Btrfs devel - Mar 2013 - [PATCH 3/4] Btrfs: remove unnecessary variant in btrfs_sector_sum structure

bytenr in btrfs_sector_sum is unnecessary, because the extents that
btrfs_sector_sum points to are continuous，we can find out the expected
checksums by btrfs_ordered_sum''s bytenr and the offset, so we can
remove btrfs_sector_sum''s bytenr.

After removing bytenr, we don''t use the while loop to get the checksums
one by one. Now, we can get several checksum value at one time. By this
way, the performance of write is improved by ~74% on my SSD (31MB/s ->
54MB/s)

test command:
 # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/file-item.c    | 144 ++++++++++++++++++------------------------------
 fs/btrfs/ordered-data.c |  21 +++----
 fs/btrfs/ordered-data.h |  25 ++-------
 fs/btrfs/relocation.c   |  10 ----
 fs/btrfs/scrub.c        |  16 ++----
 5 files changed, 72 insertions(+), 144 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 3e2f080..9a447bc 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -34,8 +34,7 @@
 
 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
 				   sizeof(struct btrfs_ordered_sum)) / \
-				   sizeof(struct btrfs_sector_sum) * \
-				   (r)->sectorsize - (r)->sectorsize)
+				   sizeof(u32) * (r)->sectorsize)
 
 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
@@ -311,7 +310,6 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_csum_item *item;
 	LIST_HEAD(tmplist);
 	unsigned long offset;
@@ -385,34 +383,28 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 				      struct btrfs_csum_item);
 		while (start < csum_end) {
 			size = min_t(size_t, csum_end - start,
-					MAX_ORDERED_SUM_BYTES(root));
+				     MAX_ORDERED_SUM_BYTES(root));
 			sums = kzalloc(btrfs_ordered_sum_size(root, size),
-					GFP_NOFS);
+				       GFP_NOFS);
 			if (!sums) {
 				ret = -ENOMEM;
 				goto fail;
 			}
 
-			sector_sum = sums->sums;
 			sums->bytenr = start;
-			sums->len = size;
+			sums->len = (int)size;
 
 			offset = (start - key.offset) >>
 				root->fs_info->sb->s_blocksize_bits;
 			offset *= csum_size;
+			size >>= root->fs_info->sb->s_blocksize_bits;
 
-			while (size > 0) {
-				read_extent_buffer(path->nodes[0],
-						&sector_sum->sum,
-						((unsigned long)item) +
-						offset, csum_size);
-				sector_sum->bytenr = start;
-
-				size -= root->sectorsize;
-				start += root->sectorsize;
-				offset += csum_size;
-				sector_sum++;
-			}
+			read_extent_buffer(path->nodes[0],
+					   sums->sums,
+					   ((unsigned long)item) + offset,
+					   csum_size * size);
+
+			start += root->sectorsize * size;
 			list_add_tail(&sums->list, &tmplist);
 		}
 		path->slots[0]++;
@@ -434,23 +426,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 		       struct bio *bio, u64 file_start, int contig)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	char *data;
 	struct bio_vec *bvec = bio->bi_io_vec;
 	int bio_index = 0;
+	int index;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
 	u64 offset;
-	u64 disk_bytenr;
 
 	WARN_ON(bio->bi_vcnt <= 0);
 	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 	if (!sums)
 		return -ENOMEM;
 
-	sector_sum = sums->sums;
-	disk_bytenr = (u64)bio->bi_sector << 9;
 	sums->len = bio->bi_size;
 	INIT_LIST_HEAD(&sums->list);
 
@@ -461,7 +450,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode
*inode,
 
 	ordered = btrfs_lookup_ordered_extent(inode, offset);
 	BUG_ON(!ordered); /* Logic error */
-	sums->bytenr = ordered->start;
+	sums->bytenr = (u64)bio->bi_sector << 9;
+	index = 0;
 
 	while (bio_index < bio->bi_vcnt) {
 		if (!contig)
@@ -480,29 +470,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 				       GFP_NOFS);
 			BUG_ON(!sums); /* -ENOMEM */
-			sector_sum = sums->sums;
 			sums->len = bytes_left;
 			ordered = btrfs_lookup_ordered_extent(inode, offset);
 			BUG_ON(!ordered); /* Logic error */
-			sums->bytenr = ordered->start;
+			sums->bytenr = ((u64)bio->bi_sector << 9) +
+				       total_bytes;
+			index = 0;
 		}
 
 		data = kmap_atomic(bvec->bv_page);
-		sector_sum->sum = ~(u32)0;
-		sector_sum->sum = btrfs_csum_data(root,
-						  data + bvec->bv_offset,
-						  sector_sum->sum,
-						  bvec->bv_len);
+		sums->sums[index] = ~(u32)0;
+		sums->sums[index] = btrfs_csum_data(root,
+						    data + bvec->bv_offset,
+						    sums->sums[index],
+						    bvec->bv_len);
 		kunmap_atomic(data);
-		btrfs_csum_final(sector_sum->sum,
-				 (char *)&sector_sum->sum);
-		sector_sum->bytenr = disk_bytenr;
+		btrfs_csum_final(sums->sums[index],
+				 (char *)(sums->sums + index));
 
-		sector_sum++;
 		bio_index++;
+		index++;
 		total_bytes += bvec->bv_len;
 		this_sum_bytes += bvec->bv_len;
-		disk_bytenr += bvec->bv_len;
 		offset += bvec->bv_len;
 		bvec++;
 	}
@@ -691,63 +680,42 @@ out:
 	return ret;
 }
 
-static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
-				 struct btrfs_sector_sum *sector_sum,
-				 u64 total_bytes, u64 sectorsize)
-{
-	u64 tmp = sectorsize;
-	u64 next_sector = sector_sum->bytenr;
-	struct btrfs_sector_sum *next = sector_sum + 1;
-
-	while ((tmp + total_bytes) < sums->len) {
-		if (next_sector + sectorsize != next->bytenr)
-			break;
-		tmp += sectorsize;
-		next_sector = next->bytenr;
-		next++;
-	}
-	return tmp;
-}
-
 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums)
 {
-	u64 bytenr;
-	int ret;
 	struct btrfs_key file_key;
 	struct btrfs_key found_key;
-	u64 next_offset;
-	u64 total_bytes = 0;
-	int found_next;
 	struct btrfs_path *path;
 	struct btrfs_csum_item *item;
 	struct btrfs_csum_item *item_end;
 	struct extent_buffer *leaf = NULL;
+	u64 next_offset;
+	u64 total_bytes = 0;
 	u64 csum_offset;
-	struct btrfs_sector_sum *sector_sum;
+	u64 bytenr;
 	u32 nritems;
 	u32 ins_size;
+	int index = 0;
+	int found_next;
+	int ret;
 	u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
-
-	sector_sum = sums->sums;
 again:
 	next_offset = (u64)-1;
 	found_next = 0;
+	bytenr = sums->bytenr + total_bytes;
 	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-	file_key.offset = sector_sum->bytenr;
-	bytenr = sector_sum->bytenr;
+	file_key.offset = bytenr;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 
-	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
+	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
 	if (!IS_ERR(item)) {
-		leaf = path->nodes[0];
-		ret = 0;
-		goto found;
+		csum_offset = 0;
+		goto csum;
 	}
 	ret = PTR_ERR(item);
 	if (ret != -EFBIG && ret != -ENOENT)
@@ -826,8 +794,7 @@ again:
 
 		free_space = btrfs_leaf_free_space(root, leaf) -
 					 sizeof(struct btrfs_item) - csum_size;
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		WARN_ON(tmp < 1);
 
@@ -850,8 +817,7 @@ insert:
 	if (found_next) {
 		u64 tmp;
 
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		tmp = min(tmp, (next_offset - file_key.offset) >>
 					 root->fs_info->sb->s_blocksize_bits);
@@ -873,30 +839,26 @@ insert:
 		goto fail_unlock;
 	}
 csum:
+	ret = 0;
 	leaf = path->nodes[0];
+
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	ret = 0;
+	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
+				      btrfs_item_size_nr(leaf, path->slots[0]));
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
-found:
-	item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
-				      btrfs_item_size_nr(leaf, path->slots[0]));
-next_sector:
 
-	write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item,
csum_size);
-
-	total_bytes += root->sectorsize;
-	sector_sum++;
-	if (total_bytes < sums->len) {
-		item = (struct btrfs_csum_item *)((char *)item +
-						  csum_size);
-		if (item < item_end && bytenr + PAGE_CACHE_SIZE =-		   
sector_sum->bytenr) {
-			bytenr = sector_sum->bytenr;
-			goto next_sector;
-		}
-	}
+	ins_size = (u32)(sums->len - total_bytes) >>
+		   root->fs_info->sb->s_blocksize_bits;
+	ins_size *= csum_size;
+	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
+			      ins_size);
+	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
+			    ins_size);
+
+	ins_size /= csum_size;
+	total_bytes += ins_size * root->sectorsize;
+	index += ins_size;
 
 	btrfs_mark_buffer_dirty(path->nodes[0]);
 	if (total_bytes < sums->len) {
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 2b959b6..23bb43a 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -987,7 +987,6 @@ int btrfs_find_ordered_sum(struct inode *inode, u64 offset,
u64 disk_bytenr,
 			   u32 *sum, int len)
 {
 	struct btrfs_ordered_sum *ordered_sum;
-	struct btrfs_sector_sum *sector_sums;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 	unsigned long num_sectors;
@@ -1004,17 +1003,15 @@ int btrfs_find_ordered_sum(struct inode *inode, u64
offset, u64 disk_bytenr,
 		if (disk_bytenr >= ordered_sum->bytenr &&
 		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len) {
 			i = (disk_bytenr - ordered_sum->bytenr) / sectorsize;
-			sector_sums = ordered_sum->sums + i;
-			num_sectors = ordered_sum->len / sectorsize;
-			for (; i < num_sectors; i++) {
-				if (sector_sums[i].bytenr == disk_bytenr) {
-					sum[index] = sector_sums[i].sum;
-					index++;
-					if (index == len)
-						goto out;
-					disk_bytenr += sectorsize;
-				}
-			}
+			num_sectors = ordered_sum->len / sectorsize - i;
+			num_sectors = min_t(int, len - index, num_sectors);
+			memcpy(sum + index, ordered_sum->sums + i,
+			       num_sectors);
+
+			index += (int)num_sectors;
+			if (index == len)
+				goto out;
+			disk_bytenr += num_sectors * sectorsize;
 		}
 	}
 out:
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 58b0e3b..888bcbb 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
 	struct rb_node *last;
 };
 
-/*
- * these are used to collect checksums done just before bios submission.
- * They are attached via a list into the ordered extent, and
- * checksum items are inserted into the tree after all the blocks in
- * the ordered extent are on disk
- */
-struct btrfs_sector_sum {
-	/* bytenr on disk */
-	u64 bytenr;
-	u32 sum;
-};
-
 struct btrfs_ordered_sum {
 	/* bytenr is the start of this extent on disk */
 	u64 bytenr;
@@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
 	/*
 	 * this is the length in bytes covered by the sums array below.
 	 */
-	unsigned long len;
+	int len;
 	struct list_head list;
-	/* last field is a variable length array of btrfs_sector_sums */
-	struct btrfs_sector_sum sums[];
+	/* last field is a variable length array of csums */
+	u32 sums[];
 };
 
 /*
@@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
 static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
 					 unsigned long bytes)
 {
-	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
-		root->sectorsize;
-	num_sectors++;
-	return sizeof(struct btrfs_ordered_sum) +
-		num_sectors * sizeof(struct btrfs_sector_sum);
+	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
+	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
 }
 
 static inline void
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3ebe879..5928142 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4335,10 +4335,8 @@ out:
 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	size_t offset;
 	int ret;
 	u64 disk_bytenr;
 	LIST_HEAD(list);
@@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64
file_pos, u64 len)
 		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
 		list_del_init(&sums->list);
 
-		sector_sum = sums->sums;
 		sums->bytenr = ordered->start;
 
-		offset = 0;
-		while (offset < sums->len) {
-			sector_sum->bytenr += ordered->start - disk_bytenr;
-			sector_sum++;
-			offset += root->sectorsize;
-		}
-
 		btrfs_add_ordered_sum(inode, ordered, sums);
 	}
 out:
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 53c3501..6c292b1 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2128,8 +2128,7 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 			   u8 *csum)
 {
 	struct btrfs_ordered_sum *sum = NULL;
-	int ret = 0;
-	unsigned long i;
+	unsigned long index;
 	unsigned long num_sectors;
 
 	while (!list_empty(&sctx->csum_list)) {
@@ -2148,19 +2147,14 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 	if (!sum)
 		return 0;
 
+	index = (logical - sum->bytenr) / sctx->sectorsize;
 	num_sectors = sum->len / sctx->sectorsize;
-	for (i = 0; i < num_sectors; ++i) {
-		if (sum->sums[i].bytenr == logical) {
-			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
-			ret = 1;
-			break;
-		}
-	}
-	if (ret && i == num_sectors - 1) {
+	memcpy(csum, sum->sums + index, sctx->csum_size);
+	if (index == num_sectors - 1) {
 		list_del(&sum->list);
 		kfree(sum);
 	}
-	return ret;
+	return 1;
 }
 
 /* scrub extent tries to collect up to 64 kB for each bio */
-- 
1.8.0.1
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bytenr in btrfs_sector_sum is unnecessary, because the extents that
btrfs_sector_sum points to are continuous, we can find out the expected
checksums by btrfs_ordered_sum''s bytenr and the offset, so we can
remove btrfs_sector_sum''s bytenr.

After removing bytenr, we don''t use the while loop to get the checksums
one by one. Now, we can get several checksum value at one time. By this
way, the performance of write is improved by ~74% on my SSD (31MB/s ->
54MB/s)

test command:
 # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
Changelog v1 -> v2:
- fix messy code in the changelog.
---
 fs/btrfs/file-item.c    | 144 ++++++++++++++++++------------------------------
 fs/btrfs/ordered-data.c |  21 +++----
 fs/btrfs/ordered-data.h |  25 ++-------
 fs/btrfs/relocation.c   |  10 ----
 fs/btrfs/scrub.c        |  16 ++----
 5 files changed, 72 insertions(+), 144 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 3e2f080..9a447bc 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -34,8 +34,7 @@
 
 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
 				   sizeof(struct btrfs_ordered_sum)) / \
-				   sizeof(struct btrfs_sector_sum) * \
-				   (r)->sectorsize - (r)->sectorsize)
+				   sizeof(u32) * (r)->sectorsize)
 
 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
@@ -311,7 +310,6 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_csum_item *item;
 	LIST_HEAD(tmplist);
 	unsigned long offset;
@@ -385,34 +383,28 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 				      struct btrfs_csum_item);
 		while (start < csum_end) {
 			size = min_t(size_t, csum_end - start,
-					MAX_ORDERED_SUM_BYTES(root));
+				     MAX_ORDERED_SUM_BYTES(root));
 			sums = kzalloc(btrfs_ordered_sum_size(root, size),
-					GFP_NOFS);
+				       GFP_NOFS);
 			if (!sums) {
 				ret = -ENOMEM;
 				goto fail;
 			}
 
-			sector_sum = sums->sums;
 			sums->bytenr = start;
-			sums->len = size;
+			sums->len = (int)size;
 
 			offset = (start - key.offset) >>
 				root->fs_info->sb->s_blocksize_bits;
 			offset *= csum_size;
+			size >>= root->fs_info->sb->s_blocksize_bits;
 
-			while (size > 0) {
-				read_extent_buffer(path->nodes[0],
-						&sector_sum->sum,
-						((unsigned long)item) +
-						offset, csum_size);
-				sector_sum->bytenr = start;
-
-				size -= root->sectorsize;
-				start += root->sectorsize;
-				offset += csum_size;
-				sector_sum++;
-			}
+			read_extent_buffer(path->nodes[0],
+					   sums->sums,
+					   ((unsigned long)item) + offset,
+					   csum_size * size);
+
+			start += root->sectorsize * size;
 			list_add_tail(&sums->list, &tmplist);
 		}
 		path->slots[0]++;
@@ -434,23 +426,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 		       struct bio *bio, u64 file_start, int contig)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	char *data;
 	struct bio_vec *bvec = bio->bi_io_vec;
 	int bio_index = 0;
+	int index;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
 	u64 offset;
-	u64 disk_bytenr;
 
 	WARN_ON(bio->bi_vcnt <= 0);
 	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 	if (!sums)
 		return -ENOMEM;
 
-	sector_sum = sums->sums;
-	disk_bytenr = (u64)bio->bi_sector << 9;
 	sums->len = bio->bi_size;
 	INIT_LIST_HEAD(&sums->list);
 
@@ -461,7 +450,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode
*inode,
 
 	ordered = btrfs_lookup_ordered_extent(inode, offset);
 	BUG_ON(!ordered); /* Logic error */
-	sums->bytenr = ordered->start;
+	sums->bytenr = (u64)bio->bi_sector << 9;
+	index = 0;
 
 	while (bio_index < bio->bi_vcnt) {
 		if (!contig)
@@ -480,29 +470,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 				       GFP_NOFS);
 			BUG_ON(!sums); /* -ENOMEM */
-			sector_sum = sums->sums;
 			sums->len = bytes_left;
 			ordered = btrfs_lookup_ordered_extent(inode, offset);
 			BUG_ON(!ordered); /* Logic error */
-			sums->bytenr = ordered->start;
+			sums->bytenr = ((u64)bio->bi_sector << 9) +
+				       total_bytes;
+			index = 0;
 		}
 
 		data = kmap_atomic(bvec->bv_page);
-		sector_sum->sum = ~(u32)0;
-		sector_sum->sum = btrfs_csum_data(root,
-						  data + bvec->bv_offset,
-						  sector_sum->sum,
-						  bvec->bv_len);
+		sums->sums[index] = ~(u32)0;
+		sums->sums[index] = btrfs_csum_data(root,
+						    data + bvec->bv_offset,
+						    sums->sums[index],
+						    bvec->bv_len);
 		kunmap_atomic(data);
-		btrfs_csum_final(sector_sum->sum,
-				 (char *)&sector_sum->sum);
-		sector_sum->bytenr = disk_bytenr;
+		btrfs_csum_final(sums->sums[index],
+				 (char *)(sums->sums + index));
 
-		sector_sum++;
 		bio_index++;
+		index++;
 		total_bytes += bvec->bv_len;
 		this_sum_bytes += bvec->bv_len;
-		disk_bytenr += bvec->bv_len;
 		offset += bvec->bv_len;
 		bvec++;
 	}
@@ -691,63 +680,42 @@ out:
 	return ret;
 }
 
-static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
-				 struct btrfs_sector_sum *sector_sum,
-				 u64 total_bytes, u64 sectorsize)
-{
-	u64 tmp = sectorsize;
-	u64 next_sector = sector_sum->bytenr;
-	struct btrfs_sector_sum *next = sector_sum + 1;
-
-	while ((tmp + total_bytes) < sums->len) {
-		if (next_sector + sectorsize != next->bytenr)
-			break;
-		tmp += sectorsize;
-		next_sector = next->bytenr;
-		next++;
-	}
-	return tmp;
-}
-
 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums)
 {
-	u64 bytenr;
-	int ret;
 	struct btrfs_key file_key;
 	struct btrfs_key found_key;
-	u64 next_offset;
-	u64 total_bytes = 0;
-	int found_next;
 	struct btrfs_path *path;
 	struct btrfs_csum_item *item;
 	struct btrfs_csum_item *item_end;
 	struct extent_buffer *leaf = NULL;
+	u64 next_offset;
+	u64 total_bytes = 0;
 	u64 csum_offset;
-	struct btrfs_sector_sum *sector_sum;
+	u64 bytenr;
 	u32 nritems;
 	u32 ins_size;
+	int index = 0;
+	int found_next;
+	int ret;
 	u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
-
-	sector_sum = sums->sums;
 again:
 	next_offset = (u64)-1;
 	found_next = 0;
+	bytenr = sums->bytenr + total_bytes;
 	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-	file_key.offset = sector_sum->bytenr;
-	bytenr = sector_sum->bytenr;
+	file_key.offset = bytenr;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 
-	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
+	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
 	if (!IS_ERR(item)) {
-		leaf = path->nodes[0];
-		ret = 0;
-		goto found;
+		csum_offset = 0;
+		goto csum;
 	}
 	ret = PTR_ERR(item);
 	if (ret != -EFBIG && ret != -ENOENT)
@@ -826,8 +794,7 @@ again:
 
 		free_space = btrfs_leaf_free_space(root, leaf) -
 					 sizeof(struct btrfs_item) - csum_size;
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		WARN_ON(tmp < 1);
 
@@ -850,8 +817,7 @@ insert:
 	if (found_next) {
 		u64 tmp;
 
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		tmp = min(tmp, (next_offset - file_key.offset) >>
 					 root->fs_info->sb->s_blocksize_bits);
@@ -873,30 +839,26 @@ insert:
 		goto fail_unlock;
 	}
 csum:
+	ret = 0;
 	leaf = path->nodes[0];
+
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	ret = 0;
+	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
+				      btrfs_item_size_nr(leaf, path->slots[0]));
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
-found:
-	item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
-				      btrfs_item_size_nr(leaf, path->slots[0]));
-next_sector:
 
-	write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item,
csum_size);
-
-	total_bytes += root->sectorsize;
-	sector_sum++;
-	if (total_bytes < sums->len) {
-		item = (struct btrfs_csum_item *)((char *)item +
-						  csum_size);
-		if (item < item_end && bytenr + PAGE_CACHE_SIZE =-		   
sector_sum->bytenr) {
-			bytenr = sector_sum->bytenr;
-			goto next_sector;
-		}
-	}
+	ins_size = (u32)(sums->len - total_bytes) >>
+		   root->fs_info->sb->s_blocksize_bits;
+	ins_size *= csum_size;
+	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
+			      ins_size);
+	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
+			    ins_size);
+
+	ins_size /= csum_size;
+	total_bytes += ins_size * root->sectorsize;
+	index += ins_size;
 
 	btrfs_mark_buffer_dirty(path->nodes[0]);
 	if (total_bytes < sums->len) {
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 2b959b6..23bb43a 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -987,7 +987,6 @@ int btrfs_find_ordered_sum(struct inode *inode, u64 offset,
u64 disk_bytenr,
 			   u32 *sum, int len)
 {
 	struct btrfs_ordered_sum *ordered_sum;
-	struct btrfs_sector_sum *sector_sums;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 	unsigned long num_sectors;
@@ -1004,17 +1003,15 @@ int btrfs_find_ordered_sum(struct inode *inode, u64
offset, u64 disk_bytenr,
 		if (disk_bytenr >= ordered_sum->bytenr &&
 		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len) {
 			i = (disk_bytenr - ordered_sum->bytenr) / sectorsize;
-			sector_sums = ordered_sum->sums + i;
-			num_sectors = ordered_sum->len / sectorsize;
-			for (; i < num_sectors; i++) {
-				if (sector_sums[i].bytenr == disk_bytenr) {
-					sum[index] = sector_sums[i].sum;
-					index++;
-					if (index == len)
-						goto out;
-					disk_bytenr += sectorsize;
-				}
-			}
+			num_sectors = ordered_sum->len / sectorsize - i;
+			num_sectors = min_t(int, len - index, num_sectors);
+			memcpy(sum + index, ordered_sum->sums + i,
+			       num_sectors);
+
+			index += (int)num_sectors;
+			if (index == len)
+				goto out;
+			disk_bytenr += num_sectors * sectorsize;
 		}
 	}
 out:
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 58b0e3b..888bcbb 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
 	struct rb_node *last;
 };
 
-/*
- * these are used to collect checksums done just before bios submission.
- * They are attached via a list into the ordered extent, and
- * checksum items are inserted into the tree after all the blocks in
- * the ordered extent are on disk
- */
-struct btrfs_sector_sum {
-	/* bytenr on disk */
-	u64 bytenr;
-	u32 sum;
-};
-
 struct btrfs_ordered_sum {
 	/* bytenr is the start of this extent on disk */
 	u64 bytenr;
@@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
 	/*
 	 * this is the length in bytes covered by the sums array below.
 	 */
-	unsigned long len;
+	int len;
 	struct list_head list;
-	/* last field is a variable length array of btrfs_sector_sums */
-	struct btrfs_sector_sum sums[];
+	/* last field is a variable length array of csums */
+	u32 sums[];
 };
 
 /*
@@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
 static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
 					 unsigned long bytes)
 {
-	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
-		root->sectorsize;
-	num_sectors++;
-	return sizeof(struct btrfs_ordered_sum) +
-		num_sectors * sizeof(struct btrfs_sector_sum);
+	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
+	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
 }
 
 static inline void
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3ebe879..5928142 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4335,10 +4335,8 @@ out:
 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	size_t offset;
 	int ret;
 	u64 disk_bytenr;
 	LIST_HEAD(list);
@@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64
file_pos, u64 len)
 		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
 		list_del_init(&sums->list);
 
-		sector_sum = sums->sums;
 		sums->bytenr = ordered->start;
 
-		offset = 0;
-		while (offset < sums->len) {
-			sector_sum->bytenr += ordered->start - disk_bytenr;
-			sector_sum++;
-			offset += root->sectorsize;
-		}
-
 		btrfs_add_ordered_sum(inode, ordered, sums);
 	}
 out:
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 53c3501..6c292b1 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2128,8 +2128,7 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 			   u8 *csum)
 {
 	struct btrfs_ordered_sum *sum = NULL;
-	int ret = 0;
-	unsigned long i;
+	unsigned long index;
 	unsigned long num_sectors;
 
 	while (!list_empty(&sctx->csum_list)) {
@@ -2148,19 +2147,14 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 	if (!sum)
 		return 0;
 
+	index = (logical - sum->bytenr) / sctx->sectorsize;
 	num_sectors = sum->len / sctx->sectorsize;
-	for (i = 0; i < num_sectors; ++i) {
-		if (sum->sums[i].bytenr == logical) {
-			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
-			ret = 1;
-			break;
-		}
-	}
-	if (ret && i == num_sectors - 1) {
+	memcpy(csum, sum->sums + index, sctx->csum_size);
+	if (index == num_sectors - 1) {
 		list_del(&sum->list);
 		kfree(sum);
 	}
-	return ret;
+	return 1;
 }
 
 /* scrub extent tries to collect up to 64 kB for each bio */
-- 
1.8.0.1

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Quoting Miao Xie (2013-03-28 05:03:52)
> bytenr in btrfs_sector_sum is unnecessary, because the extents that
> btrfs_sector_sum points to are continuous, we can find out the expected
> checksums by btrfs_ordered_sum''s bytenr and the offset, so we can
> remove btrfs_sector_sum''s bytenr.
I really like these, thanks for speeding up the crcs.

-chris
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On Thu, Mar 28, 2013 at 04:11:38PM +0800, Miao Xie
wrote:
> bytenr in btrfs_sector_sum is unnecessary, because the extents that
> btrfs_sector_sum points to are continuous，we can find out the expected
> checksums by btrfs_ordered_sum''s bytenr and the offset, so we can
> remove btrfs_sector_sum''s bytenr.
> 
> After removing bytenr, we don''t use the while loop to get the
checksums
> one by one. Now, we can get several checksum value at one time. By this
> way, the performance of write is improved by ~74% on my SSD (31MB/s ->
54MB/s)
> 
> test command:
>  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
Looks good to me.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> 
> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
> ---
>  fs/btrfs/file-item.c    | 144
++++++++++++++++++------------------------------
>  fs/btrfs/ordered-data.c |  21 +++----
>  fs/btrfs/ordered-data.h |  25 ++-------
>  fs/btrfs/relocation.c   |  10 ----
>  fs/btrfs/scrub.c        |  16 ++----
>  5 files changed, 72 insertions(+), 144 deletions(-)
> 
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index 3e2f080..9a447bc 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -34,8 +34,7 @@
>  
>  #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
>  				   sizeof(struct btrfs_ordered_sum)) / \
> -				   sizeof(struct btrfs_sector_sum) * \
> -				   (r)->sectorsize - (r)->sectorsize)
> +				   sizeof(u32) * (r)->sectorsize)
>  
>  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
>  			     struct btrfs_root *root,
> @@ -311,7 +310,6 @@ int btrfs_lookup_csums_range(struct btrfs_root *root,
u64 start, u64 end,
>  	struct btrfs_path *path;
>  	struct extent_buffer *leaf;
>  	struct btrfs_ordered_sum *sums;
> -	struct btrfs_sector_sum *sector_sum;
>  	struct btrfs_csum_item *item;
>  	LIST_HEAD(tmplist);
>  	unsigned long offset;
> @@ -385,34 +383,28 @@ int btrfs_lookup_csums_range(struct btrfs_root *root,
u64 start, u64 end,
>  				      struct btrfs_csum_item);
>  		while (start < csum_end) {
>  			size = min_t(size_t, csum_end - start,
> -					MAX_ORDERED_SUM_BYTES(root));
> +				     MAX_ORDERED_SUM_BYTES(root));
>  			sums = kzalloc(btrfs_ordered_sum_size(root, size),
> -					GFP_NOFS);
> +				       GFP_NOFS);
>  			if (!sums) {
>  				ret = -ENOMEM;
>  				goto fail;
>  			}
>  
> -			sector_sum = sums->sums;
>  			sums->bytenr = start;
> -			sums->len = size;
> +			sums->len = (int)size;
>  
>  			offset = (start - key.offset) >>
>  				root->fs_info->sb->s_blocksize_bits;
>  			offset *= csum_size;
> +			size >>= root->fs_info->sb->s_blocksize_bits;
>  
> -			while (size > 0) {
> -				read_extent_buffer(path->nodes[0],
> -						&sector_sum->sum,
> -						((unsigned long)item) +
> -						offset, csum_size);
> -				sector_sum->bytenr = start;
> -
> -				size -= root->sectorsize;
> -				start += root->sectorsize;
> -				offset += csum_size;
> -				sector_sum++;
> -			}
> +			read_extent_buffer(path->nodes[0],
> +					   sums->sums,
> +					   ((unsigned long)item) + offset,
> +					   csum_size * size);
> +
> +			start += root->sectorsize * size;
>  			list_add_tail(&sums->list, &tmplist);
>  		}
>  		path->slots[0]++;
> @@ -434,23 +426,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
>  		       struct bio *bio, u64 file_start, int contig)
>  {
>  	struct btrfs_ordered_sum *sums;
> -	struct btrfs_sector_sum *sector_sum;
>  	struct btrfs_ordered_extent *ordered;
>  	char *data;
>  	struct bio_vec *bvec = bio->bi_io_vec;
>  	int bio_index = 0;
> +	int index;
>  	unsigned long total_bytes = 0;
>  	unsigned long this_sum_bytes = 0;
>  	u64 offset;
> -	u64 disk_bytenr;
>  
>  	WARN_ON(bio->bi_vcnt <= 0);
>  	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
>  	if (!sums)
>  		return -ENOMEM;
>  
> -	sector_sum = sums->sums;
> -	disk_bytenr = (u64)bio->bi_sector << 9;
>  	sums->len = bio->bi_size;
>  	INIT_LIST_HEAD(&sums->list);
>  
> @@ -461,7 +450,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
>  
>  	ordered = btrfs_lookup_ordered_extent(inode, offset);
>  	BUG_ON(!ordered); /* Logic error */
> -	sums->bytenr = ordered->start;
> +	sums->bytenr = (u64)bio->bi_sector << 9;
> +	index = 0;
>  
>  	while (bio_index < bio->bi_vcnt) {
>  		if (!contig)
> @@ -480,29 +470,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
>  			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
>  				       GFP_NOFS);
>  			BUG_ON(!sums); /* -ENOMEM */
> -			sector_sum = sums->sums;
>  			sums->len = bytes_left;
>  			ordered = btrfs_lookup_ordered_extent(inode, offset);
>  			BUG_ON(!ordered); /* Logic error */
> -			sums->bytenr = ordered->start;
> +			sums->bytenr = ((u64)bio->bi_sector << 9) +
> +				       total_bytes;
> +			index = 0;
>  		}
>  
>  		data = kmap_atomic(bvec->bv_page);
> -		sector_sum->sum = ~(u32)0;
> -		sector_sum->sum = btrfs_csum_data(root,
> -						  data + bvec->bv_offset,
> -						  sector_sum->sum,
> -						  bvec->bv_len);
> +		sums->sums[index] = ~(u32)0;
> +		sums->sums[index] = btrfs_csum_data(root,
> +						    data + bvec->bv_offset,
> +						    sums->sums[index],
> +						    bvec->bv_len);
>  		kunmap_atomic(data);
> -		btrfs_csum_final(sector_sum->sum,
> -				 (char *)&sector_sum->sum);
> -		sector_sum->bytenr = disk_bytenr;
> +		btrfs_csum_final(sums->sums[index],
> +				 (char *)(sums->sums + index));
>  
> -		sector_sum++;
>  		bio_index++;
> +		index++;
>  		total_bytes += bvec->bv_len;
>  		this_sum_bytes += bvec->bv_len;
> -		disk_bytenr += bvec->bv_len;
>  		offset += bvec->bv_len;
>  		bvec++;
>  	}
> @@ -691,63 +680,42 @@ out:
>  	return ret;
>  }
>  
> -static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
> -				 struct btrfs_sector_sum *sector_sum,
> -				 u64 total_bytes, u64 sectorsize)
> -{
> -	u64 tmp = sectorsize;
> -	u64 next_sector = sector_sum->bytenr;
> -	struct btrfs_sector_sum *next = sector_sum + 1;
> -
> -	while ((tmp + total_bytes) < sums->len) {
> -		if (next_sector + sectorsize != next->bytenr)
> -			break;
> -		tmp += sectorsize;
> -		next_sector = next->bytenr;
> -		next++;
> -	}
> -	return tmp;
> -}
> -
>  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
>  			   struct btrfs_root *root,
>  			   struct btrfs_ordered_sum *sums)
>  {
> -	u64 bytenr;
> -	int ret;
>  	struct btrfs_key file_key;
>  	struct btrfs_key found_key;
> -	u64 next_offset;
> -	u64 total_bytes = 0;
> -	int found_next;
>  	struct btrfs_path *path;
>  	struct btrfs_csum_item *item;
>  	struct btrfs_csum_item *item_end;
>  	struct extent_buffer *leaf = NULL;
> +	u64 next_offset;
> +	u64 total_bytes = 0;
>  	u64 csum_offset;
> -	struct btrfs_sector_sum *sector_sum;
> +	u64 bytenr;
>  	u32 nritems;
>  	u32 ins_size;
> +	int index = 0;
> +	int found_next;
> +	int ret;
>  	u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
>  
>  	path = btrfs_alloc_path();
>  	if (!path)
>  		return -ENOMEM;
> -
> -	sector_sum = sums->sums;
>  again:
>  	next_offset = (u64)-1;
>  	found_next = 0;
> +	bytenr = sums->bytenr + total_bytes;
>  	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
> -	file_key.offset = sector_sum->bytenr;
> -	bytenr = sector_sum->bytenr;
> +	file_key.offset = bytenr;
>  	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
>  
> -	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
> +	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
>  	if (!IS_ERR(item)) {
> -		leaf = path->nodes[0];
> -		ret = 0;
> -		goto found;
> +		csum_offset = 0;
> +		goto csum;
>  	}
>  	ret = PTR_ERR(item);
>  	if (ret != -EFBIG && ret != -ENOENT)
> @@ -826,8 +794,7 @@ again:
>  
>  		free_space = btrfs_leaf_free_space(root, leaf) -
>  					 sizeof(struct btrfs_item) - csum_size;
> -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
> -					    root->sectorsize);
> +		tmp = sums->len - total_bytes;
>  		tmp >>= root->fs_info->sb->s_blocksize_bits;
>  		WARN_ON(tmp < 1);
>  
> @@ -850,8 +817,7 @@ insert:
>  	if (found_next) {
>  		u64 tmp;
>  
> -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
> -					    root->sectorsize);
> +		tmp = sums->len - total_bytes;
>  		tmp >>= root->fs_info->sb->s_blocksize_bits;
>  		tmp = min(tmp, (next_offset - file_key.offset) >>
>  					 root->fs_info->sb->s_blocksize_bits);
> @@ -873,30 +839,26 @@ insert:
>  		goto fail_unlock;
>  	}
>  csum:
> +	ret = 0;
>  	leaf = path->nodes[0];
> +
>  	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
> -	ret = 0;
> +	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
> +				      btrfs_item_size_nr(leaf, path->slots[0]));
>  	item = (struct btrfs_csum_item *)((unsigned char *)item +
>  					  csum_offset * csum_size);
> -found:
> -	item_end = btrfs_item_ptr(leaf, path->slots[0], struct
btrfs_csum_item);
> -	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
> -				      btrfs_item_size_nr(leaf, path->slots[0]));
> -next_sector:
>  
> -	write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item,
csum_size);
> -
> -	total_bytes += root->sectorsize;
> -	sector_sum++;
> -	if (total_bytes < sums->len) {
> -		item = (struct btrfs_csum_item *)((char *)item +
> -						  csum_size);
> -		if (item < item_end && bytenr + PAGE_CACHE_SIZE => -		   
sector_sum->bytenr) {
> -			bytenr = sector_sum->bytenr;
> -			goto next_sector;
> -		}
> -	}
> +	ins_size = (u32)(sums->len - total_bytes) >>
> +		   root->fs_info->sb->s_blocksize_bits;
> +	ins_size *= csum_size;
> +	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
> +			      ins_size);
> +	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
> +			    ins_size);
> +
> +	ins_size /= csum_size;
> +	total_bytes += ins_size * root->sectorsize;
> +	index += ins_size;
>  
>  	btrfs_mark_buffer_dirty(path->nodes[0]);
>  	if (total_bytes < sums->len) {
> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> index 2b959b6..23bb43a 100644
> --- a/fs/btrfs/ordered-data.c
> +++ b/fs/btrfs/ordered-data.c
> @@ -987,7 +987,6 @@ int btrfs_find_ordered_sum(struct inode *inode, u64
offset, u64 disk_bytenr,
>  			   u32 *sum, int len)
>  {
>  	struct btrfs_ordered_sum *ordered_sum;
> -	struct btrfs_sector_sum *sector_sums;
>  	struct btrfs_ordered_extent *ordered;
>  	struct btrfs_ordered_inode_tree *tree =
&BTRFS_I(inode)->ordered_tree;
>  	unsigned long num_sectors;
> @@ -1004,17 +1003,15 @@ int btrfs_find_ordered_sum(struct inode *inode, u64
offset, u64 disk_bytenr,
>  		if (disk_bytenr >= ordered_sum->bytenr &&
>  		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len) {
>  			i = (disk_bytenr - ordered_sum->bytenr) / sectorsize;
> -			sector_sums = ordered_sum->sums + i;
> -			num_sectors = ordered_sum->len / sectorsize;
> -			for (; i < num_sectors; i++) {
> -				if (sector_sums[i].bytenr == disk_bytenr) {
> -					sum[index] = sector_sums[i].sum;
> -					index++;
> -					if (index == len)
> -						goto out;
> -					disk_bytenr += sectorsize;
> -				}
> -			}
> +			num_sectors = ordered_sum->len / sectorsize - i;
> +			num_sectors = min_t(int, len - index, num_sectors);
> +			memcpy(sum + index, ordered_sum->sums + i,
> +			       num_sectors);
> +
> +			index += (int)num_sectors;
> +			if (index == len)
> +				goto out;
> +			disk_bytenr += num_sectors * sectorsize;
>  		}
>  	}
>  out:
> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> index 58b0e3b..888bcbb 100644
> --- a/fs/btrfs/ordered-data.h
> +++ b/fs/btrfs/ordered-data.h
> @@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
>  	struct rb_node *last;
>  };
>  
> -/*
> - * these are used to collect checksums done just before bios submission.
> - * They are attached via a list into the ordered extent, and
> - * checksum items are inserted into the tree after all the blocks in
> - * the ordered extent are on disk
> - */
> -struct btrfs_sector_sum {
> -	/* bytenr on disk */
> -	u64 bytenr;
> -	u32 sum;
> -};
> -
>  struct btrfs_ordered_sum {
>  	/* bytenr is the start of this extent on disk */
>  	u64 bytenr;
> @@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
>  	/*
>  	 * this is the length in bytes covered by the sums array below.
>  	 */
> -	unsigned long len;
> +	int len;
>  	struct list_head list;
> -	/* last field is a variable length array of btrfs_sector_sums */
> -	struct btrfs_sector_sum sums[];
> +	/* last field is a variable length array of csums */
> +	u32 sums[];
>  };
>  
>  /*
> @@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
>  static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
>  					 unsigned long bytes)
>  {
> -	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
> -		root->sectorsize;
> -	num_sectors++;
> -	return sizeof(struct btrfs_ordered_sum) +
> -		num_sectors * sizeof(struct btrfs_sector_sum);
> +	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
> +	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
>  }
>  
>  static inline void
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 3ebe879..5928142 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4335,10 +4335,8 @@ out:
>  int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
>  {
>  	struct btrfs_ordered_sum *sums;
> -	struct btrfs_sector_sum *sector_sum;
>  	struct btrfs_ordered_extent *ordered;
>  	struct btrfs_root *root = BTRFS_I(inode)->root;
> -	size_t offset;
>  	int ret;
>  	u64 disk_bytenr;
>  	LIST_HEAD(list);
> @@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64
file_pos, u64 len)
>  		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
>  		list_del_init(&sums->list);
>  
> -		sector_sum = sums->sums;
>  		sums->bytenr = ordered->start;
>  
> -		offset = 0;
> -		while (offset < sums->len) {
> -			sector_sum->bytenr += ordered->start - disk_bytenr;
> -			sector_sum++;
> -			offset += root->sectorsize;
> -		}
> -
>  		btrfs_add_ordered_sum(inode, ordered, sums);
>  	}
>  out:
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 53c3501..6c292b1 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2128,8 +2128,7 @@ static int scrub_find_csum(struct scrub_ctx *sctx,
u64 logical, u64 len,
>  			   u8 *csum)
>  {
>  	struct btrfs_ordered_sum *sum = NULL;
> -	int ret = 0;
> -	unsigned long i;
> +	unsigned long index;
>  	unsigned long num_sectors;
>  
>  	while (!list_empty(&sctx->csum_list)) {
> @@ -2148,19 +2147,14 @@ static int scrub_find_csum(struct scrub_ctx *sctx,
u64 logical, u64 len,
>  	if (!sum)
>  		return 0;
>  
> +	index = (logical - sum->bytenr) / sctx->sectorsize;
>  	num_sectors = sum->len / sctx->sectorsize;
> -	for (i = 0; i < num_sectors; ++i) {
> -		if (sum->sums[i].bytenr == logical) {
> -			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
> -			ret = 1;
> -			break;
> -		}
> -	}
> -	if (ret && i == num_sectors - 1) {
> +	memcpy(csum, sum->sums + index, sctx->csum_size);
> +	if (index == num_sectors - 1) {
>  		list_del(&sum->list);
>  		kfree(sum);
>  	}
> -	return ret;
> +	return 1;
>  }
>  
>  /* scrub extent tries to collect up to 64 kB for each bio */
> -- 
> 1.8.0.1
> --
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On Thu, Mar 28, 2013 at 10:38:34PM +0800, Liu Bo wrote:
> On Thu, Mar 28, 2013 at 04:11:38PM +0800, Miao Xie wrote:
> > bytenr in btrfs_sector_sum is unnecessary, because the extents that
> > btrfs_sector_sum points to are continuous，we can find out the expected
> > checksums by btrfs_ordered_sum''s bytenr and the offset, so we
can
> > remove btrfs_sector_sum''s bytenr.
> > 
> > After removing bytenr, we don''t use the while loop to get the
checksums
> > one by one. Now, we can get several checksum value at one time. By
this
> > way, the performance of write is improved by ~74% on my SSD (31MB/s
-> 54MB/s)
> > 
> > test command:
> >  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
but the title is a bit confused because you''ve actually killed all of
btrfs_sector_sum.
> 
> Looks good to me.
> 
> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> 
> > 
> > Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
> > ---
> >  fs/btrfs/file-item.c    | 144
++++++++++++++++++------------------------------
> >  fs/btrfs/ordered-data.c |  21 +++----
> >  fs/btrfs/ordered-data.h |  25 ++-------
> >  fs/btrfs/relocation.c   |  10 ----
> >  fs/btrfs/scrub.c        |  16 ++----
> >  5 files changed, 72 insertions(+), 144 deletions(-)
> > 
> > diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> > index 3e2f080..9a447bc 100644
> > --- a/fs/btrfs/file-item.c
> > +++ b/fs/btrfs/file-item.c
> > @@ -34,8 +34,7 @@
> >  
> >  #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
> >  				   sizeof(struct btrfs_ordered_sum)) / \
> > -				   sizeof(struct btrfs_sector_sum) * \
> > -				   (r)->sectorsize - (r)->sectorsize)
> > +				   sizeof(u32) * (r)->sectorsize)
> >  
> >  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
> >  			     struct btrfs_root *root,
> > @@ -311,7 +310,6 @@ int btrfs_lookup_csums_range(struct btrfs_root
*root, u64 start, u64 end,
> >  	struct btrfs_path *path;
> >  	struct extent_buffer *leaf;
> >  	struct btrfs_ordered_sum *sums;
> > -	struct btrfs_sector_sum *sector_sum;
> >  	struct btrfs_csum_item *item;
> >  	LIST_HEAD(tmplist);
> >  	unsigned long offset;
> > @@ -385,34 +383,28 @@ int btrfs_lookup_csums_range(struct btrfs_root
*root, u64 start, u64 end,
> >  				      struct btrfs_csum_item);
> >  		while (start < csum_end) {
> >  			size = min_t(size_t, csum_end - start,
> > -					MAX_ORDERED_SUM_BYTES(root));
> > +				     MAX_ORDERED_SUM_BYTES(root));
> >  			sums = kzalloc(btrfs_ordered_sum_size(root, size),
> > -					GFP_NOFS);
> > +				       GFP_NOFS);
> >  			if (!sums) {
> >  				ret = -ENOMEM;
> >  				goto fail;
> >  			}
> >  
> > -			sector_sum = sums->sums;
> >  			sums->bytenr = start;
> > -			sums->len = size;
> > +			sums->len = (int)size;
> >  
> >  			offset = (start - key.offset) >>
> >  				root->fs_info->sb->s_blocksize_bits;
> >  			offset *= csum_size;
> > +			size >>= root->fs_info->sb->s_blocksize_bits;
> >  
> > -			while (size > 0) {
> > -				read_extent_buffer(path->nodes[0],
> > -						&sector_sum->sum,
> > -						((unsigned long)item) +
> > -						offset, csum_size);
> > -				sector_sum->bytenr = start;
> > -
> > -				size -= root->sectorsize;
> > -				start += root->sectorsize;
> > -				offset += csum_size;
> > -				sector_sum++;
> > -			}
> > +			read_extent_buffer(path->nodes[0],
> > +					   sums->sums,
> > +					   ((unsigned long)item) + offset,
> > +					   csum_size * size);
> > +
> > +			start += root->sectorsize * size;
> >  			list_add_tail(&sums->list, &tmplist);
> >  		}
> >  		path->slots[0]++;
> > @@ -434,23 +426,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
> >  		       struct bio *bio, u64 file_start, int contig)
> >  {
> >  	struct btrfs_ordered_sum *sums;
> > -	struct btrfs_sector_sum *sector_sum;
> >  	struct btrfs_ordered_extent *ordered;
> >  	char *data;
> >  	struct bio_vec *bvec = bio->bi_io_vec;
> >  	int bio_index = 0;
> > +	int index;
> >  	unsigned long total_bytes = 0;
> >  	unsigned long this_sum_bytes = 0;
> >  	u64 offset;
> > -	u64 disk_bytenr;
> >  
> >  	WARN_ON(bio->bi_vcnt <= 0);
> >  	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size),
GFP_NOFS);
> >  	if (!sums)
> >  		return -ENOMEM;
> >  
> > -	sector_sum = sums->sums;
> > -	disk_bytenr = (u64)bio->bi_sector << 9;
> >  	sums->len = bio->bi_size;
> >  	INIT_LIST_HEAD(&sums->list);
> >  
> > @@ -461,7 +450,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
> >  
> >  	ordered = btrfs_lookup_ordered_extent(inode, offset);
> >  	BUG_ON(!ordered); /* Logic error */
> > -	sums->bytenr = ordered->start;
> > +	sums->bytenr = (u64)bio->bi_sector << 9;
> > +	index = 0;
> >  
> >  	while (bio_index < bio->bi_vcnt) {
> >  		if (!contig)
> > @@ -480,29 +470,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
> >  			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
> >  				       GFP_NOFS);
> >  			BUG_ON(!sums); /* -ENOMEM */
> > -			sector_sum = sums->sums;
> >  			sums->len = bytes_left;
> >  			ordered = btrfs_lookup_ordered_extent(inode, offset);
> >  			BUG_ON(!ordered); /* Logic error */
> > -			sums->bytenr = ordered->start;
> > +			sums->bytenr = ((u64)bio->bi_sector << 9) +
> > +				       total_bytes;
> > +			index = 0;
> >  		}
> >  
> >  		data = kmap_atomic(bvec->bv_page);
> > -		sector_sum->sum = ~(u32)0;
> > -		sector_sum->sum = btrfs_csum_data(root,
> > -						  data + bvec->bv_offset,
> > -						  sector_sum->sum,
> > -						  bvec->bv_len);
> > +		sums->sums[index] = ~(u32)0;
> > +		sums->sums[index] = btrfs_csum_data(root,
> > +						    data + bvec->bv_offset,
> > +						    sums->sums[index],
> > +						    bvec->bv_len);
> >  		kunmap_atomic(data);
> > -		btrfs_csum_final(sector_sum->sum,
> > -				 (char *)&sector_sum->sum);
> > -		sector_sum->bytenr = disk_bytenr;
> > +		btrfs_csum_final(sums->sums[index],
> > +				 (char *)(sums->sums + index));
> >  
> > -		sector_sum++;
> >  		bio_index++;
> > +		index++;
> >  		total_bytes += bvec->bv_len;
> >  		this_sum_bytes += bvec->bv_len;
> > -		disk_bytenr += bvec->bv_len;
> >  		offset += bvec->bv_len;
> >  		bvec++;
> >  	}
> > @@ -691,63 +680,42 @@ out:
> >  	return ret;
> >  }
> >  
> > -static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
> > -				 struct btrfs_sector_sum *sector_sum,
> > -				 u64 total_bytes, u64 sectorsize)
> > -{
> > -	u64 tmp = sectorsize;
> > -	u64 next_sector = sector_sum->bytenr;
> > -	struct btrfs_sector_sum *next = sector_sum + 1;
> > -
> > -	while ((tmp + total_bytes) < sums->len) {
> > -		if (next_sector + sectorsize != next->bytenr)
> > -			break;
> > -		tmp += sectorsize;
> > -		next_sector = next->bytenr;
> > -		next++;
> > -	}
> > -	return tmp;
> > -}
> > -
> >  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
> >  			   struct btrfs_root *root,
> >  			   struct btrfs_ordered_sum *sums)
> >  {
> > -	u64 bytenr;
> > -	int ret;
> >  	struct btrfs_key file_key;
> >  	struct btrfs_key found_key;
> > -	u64 next_offset;
> > -	u64 total_bytes = 0;
> > -	int found_next;
> >  	struct btrfs_path *path;
> >  	struct btrfs_csum_item *item;
> >  	struct btrfs_csum_item *item_end;
> >  	struct extent_buffer *leaf = NULL;
> > +	u64 next_offset;
> > +	u64 total_bytes = 0;
> >  	u64 csum_offset;
> > -	struct btrfs_sector_sum *sector_sum;
> > +	u64 bytenr;
> >  	u32 nritems;
> >  	u32 ins_size;
> > +	int index = 0;
> > +	int found_next;
> > +	int ret;
> >  	u16 csum_size =
btrfs_super_csum_size(root->fs_info->super_copy);
> >  
> >  	path = btrfs_alloc_path();
> >  	if (!path)
> >  		return -ENOMEM;
> > -
> > -	sector_sum = sums->sums;
> >  again:
> >  	next_offset = (u64)-1;
> >  	found_next = 0;
> > +	bytenr = sums->bytenr + total_bytes;
> >  	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
> > -	file_key.offset = sector_sum->bytenr;
> > -	bytenr = sector_sum->bytenr;
> > +	file_key.offset = bytenr;
> >  	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
> >  
> > -	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr,
1);
> > +	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
> >  	if (!IS_ERR(item)) {
> > -		leaf = path->nodes[0];
> > -		ret = 0;
> > -		goto found;
> > +		csum_offset = 0;
> > +		goto csum;
> >  	}
> >  	ret = PTR_ERR(item);
> >  	if (ret != -EFBIG && ret != -ENOENT)
> > @@ -826,8 +794,7 @@ again:
> >  
> >  		free_space = btrfs_leaf_free_space(root, leaf) -
> >  					 sizeof(struct btrfs_item) - csum_size;
> > -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
> > -					    root->sectorsize);
> > +		tmp = sums->len - total_bytes;
> >  		tmp >>= root->fs_info->sb->s_blocksize_bits;
> >  		WARN_ON(tmp < 1);
> >  
> > @@ -850,8 +817,7 @@ insert:
> >  	if (found_next) {
> >  		u64 tmp;
> >  
> > -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
> > -					    root->sectorsize);
> > +		tmp = sums->len - total_bytes;
> >  		tmp >>= root->fs_info->sb->s_blocksize_bits;
> >  		tmp = min(tmp, (next_offset - file_key.offset) >>
> >  					 root->fs_info->sb->s_blocksize_bits);
> > @@ -873,30 +839,26 @@ insert:
> >  		goto fail_unlock;
> >  	}
> >  csum:
> > +	ret = 0;
> >  	leaf = path->nodes[0];
> > +
> >  	item = btrfs_item_ptr(leaf, path->slots[0], struct
btrfs_csum_item);
> > -	ret = 0;
> > +	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
> > +				      btrfs_item_size_nr(leaf, path->slots[0]));
> >  	item = (struct btrfs_csum_item *)((unsigned char *)item +
> >  					  csum_offset * csum_size);
> > -found:
> > -	item_end = btrfs_item_ptr(leaf, path->slots[0], struct
btrfs_csum_item);
> > -	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
> > -				      btrfs_item_size_nr(leaf, path->slots[0]));
> > -next_sector:
> >  
> > -	write_extent_buffer(leaf, &sector_sum->sum, (unsigned
long)item, csum_size);
> > -
> > -	total_bytes += root->sectorsize;
> > -	sector_sum++;
> > -	if (total_bytes < sums->len) {
> > -		item = (struct btrfs_csum_item *)((char *)item +
> > -						  csum_size);
> > -		if (item < item_end && bytenr + PAGE_CACHE_SIZE =>
> -		    sector_sum->bytenr) {
> > -			bytenr = sector_sum->bytenr;
> > -			goto next_sector;
> > -		}
> > -	}
> > +	ins_size = (u32)(sums->len - total_bytes) >>
> > +		   root->fs_info->sb->s_blocksize_bits;
> > +	ins_size *= csum_size;
> > +	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
> > +			      ins_size);
> > +	write_extent_buffer(leaf, sums->sums + index, (unsigned
long)item,
> > +			    ins_size);
> > +
> > +	ins_size /= csum_size;
> > +	total_bytes += ins_size * root->sectorsize;
> > +	index += ins_size;
> >  
> >  	btrfs_mark_buffer_dirty(path->nodes[0]);
> >  	if (total_bytes < sums->len) {
> > diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> > index 2b959b6..23bb43a 100644
> > --- a/fs/btrfs/ordered-data.c
> > +++ b/fs/btrfs/ordered-data.c
> > @@ -987,7 +987,6 @@ int btrfs_find_ordered_sum(struct inode *inode,
u64 offset, u64 disk_bytenr,
> >  			   u32 *sum, int len)
> >  {
> >  	struct btrfs_ordered_sum *ordered_sum;
> > -	struct btrfs_sector_sum *sector_sums;
> >  	struct btrfs_ordered_extent *ordered;
> >  	struct btrfs_ordered_inode_tree *tree =
&BTRFS_I(inode)->ordered_tree;
> >  	unsigned long num_sectors;
> > @@ -1004,17 +1003,15 @@ int btrfs_find_ordered_sum(struct inode
*inode, u64 offset, u64 disk_bytenr,
> >  		if (disk_bytenr >= ordered_sum->bytenr &&
> >  		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len)
{
> >  			i = (disk_bytenr - ordered_sum->bytenr) / sectorsize;
> > -			sector_sums = ordered_sum->sums + i;
> > -			num_sectors = ordered_sum->len / sectorsize;
> > -			for (; i < num_sectors; i++) {
> > -				if (sector_sums[i].bytenr == disk_bytenr) {
> > -					sum[index] = sector_sums[i].sum;
> > -					index++;
> > -					if (index == len)
> > -						goto out;
> > -					disk_bytenr += sectorsize;
> > -				}
> > -			}
> > +			num_sectors = ordered_sum->len / sectorsize - i;
> > +			num_sectors = min_t(int, len - index, num_sectors);
> > +			memcpy(sum + index, ordered_sum->sums + i,
> > +			       num_sectors);
> > +
> > +			index += (int)num_sectors;
> > +			if (index == len)
> > +				goto out;
> > +			disk_bytenr += num_sectors * sectorsize;
> >  		}
> >  	}
> >  out:
> > diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> > index 58b0e3b..888bcbb 100644
> > --- a/fs/btrfs/ordered-data.h
> > +++ b/fs/btrfs/ordered-data.h
> > @@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
> >  	struct rb_node *last;
> >  };
> >  
> > -/*
> > - * these are used to collect checksums done just before bios
submission.
> > - * They are attached via a list into the ordered extent, and
> > - * checksum items are inserted into the tree after all the blocks in
> > - * the ordered extent are on disk
> > - */
> > -struct btrfs_sector_sum {
> > -	/* bytenr on disk */
> > -	u64 bytenr;
> > -	u32 sum;
> > -};
> > -
> >  struct btrfs_ordered_sum {
> >  	/* bytenr is the start of this extent on disk */
> >  	u64 bytenr;
> > @@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
> >  	/*
> >  	 * this is the length in bytes covered by the sums array below.
> >  	 */
> > -	unsigned long len;
> > +	int len;
> >  	struct list_head list;
> > -	/* last field is a variable length array of btrfs_sector_sums */
> > -	struct btrfs_sector_sum sums[];
> > +	/* last field is a variable length array of csums */
> > +	u32 sums[];
> >  };
> >  
> >  /*
> > @@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
> >  static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
> >  					 unsigned long bytes)
> >  {
> > -	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
> > -		root->sectorsize;
> > -	num_sectors++;
> > -	return sizeof(struct btrfs_ordered_sum) +
> > -		num_sectors * sizeof(struct btrfs_sector_sum);
> > +	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
> > +	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
> >  }
> >  
> >  static inline void
> > diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> > index 3ebe879..5928142 100644
> > --- a/fs/btrfs/relocation.c
> > +++ b/fs/btrfs/relocation.c
> > @@ -4335,10 +4335,8 @@ out:
> >  int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64
len)
> >  {
> >  	struct btrfs_ordered_sum *sums;
> > -	struct btrfs_sector_sum *sector_sum;
> >  	struct btrfs_ordered_extent *ordered;
> >  	struct btrfs_root *root = BTRFS_I(inode)->root;
> > -	size_t offset;
> >  	int ret;
> >  	u64 disk_bytenr;
> >  	LIST_HEAD(list);
> > @@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode
*inode, u64 file_pos, u64 len)
> >  		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
> >  		list_del_init(&sums->list);
> >  
> > -		sector_sum = sums->sums;
> >  		sums->bytenr = ordered->start;
> >  
> > -		offset = 0;
> > -		while (offset < sums->len) {
> > -			sector_sum->bytenr += ordered->start - disk_bytenr;
> > -			sector_sum++;
> > -			offset += root->sectorsize;
> > -		}
> > -
> >  		btrfs_add_ordered_sum(inode, ordered, sums);
> >  	}
> >  out:
> > diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> > index 53c3501..6c292b1 100644
> > --- a/fs/btrfs/scrub.c
> > +++ b/fs/btrfs/scrub.c
> > @@ -2128,8 +2128,7 @@ static int scrub_find_csum(struct scrub_ctx
*sctx, u64 logical, u64 len,
> >  			   u8 *csum)
> >  {
> >  	struct btrfs_ordered_sum *sum = NULL;
> > -	int ret = 0;
> > -	unsigned long i;
> > +	unsigned long index;
> >  	unsigned long num_sectors;
> >  
> >  	while (!list_empty(&sctx->csum_list)) {
> > @@ -2148,19 +2147,14 @@ static int scrub_find_csum(struct scrub_ctx
*sctx, u64 logical, u64 len,
> >  	if (!sum)
> >  		return 0;
> >  
> > +	index = (logical - sum->bytenr) / sctx->sectorsize;
> >  	num_sectors = sum->len / sctx->sectorsize;
> > -	for (i = 0; i < num_sectors; ++i) {
> > -		if (sum->sums[i].bytenr == logical) {
> > -			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
> > -			ret = 1;
> > -			break;
> > -		}
> > -	}
> > -	if (ret && i == num_sectors - 1) {
> > +	memcpy(csum, sum->sums + index, sctx->csum_size);
> > +	if (index == num_sectors - 1) {
> >  		list_del(&sum->list);
> >  		kfree(sum);
> >  	}
> > -	return ret;
> > +	return 1;
> >  }
> >  
> >  /* scrub extent tries to collect up to 64 kB for each bio */
> > -- 
> > 1.8.0.1
> > --
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On Thu, 28 Mar 2013 22:41:50 +0800, Liu Bo wrote:
> On Thu, Mar 28, 2013 at 10:38:34PM +0800, Liu Bo wrote:
>> On Thu, Mar 28, 2013 at 04:11:38PM +0800, Miao Xie wrote:
>>> bytenr in btrfs_sector_sum is unnecessary, because the extents that
>>> btrfs_sector_sum points to are continuous，we can find out the
expected
>>> checksums by btrfs_ordered_sum''s bytenr and the offset, so
we can
>>> remove btrfs_sector_sum''s bytenr.
>>>
>>> After removing bytenr, we don''t use the while loop to get
the checksums
>>> one by one. Now, we can get several checksum value at one time. By
this
>>> way, the performance of write is improved by ~74% on my SSD (31MB/s
-> 54MB/s)
>>>
>>> test command:
>>>  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
> 
> but the title is a bit confused because you''ve actually killed all
of
> btrfs_sector_sum.
I misused the old title, will change it later.

Thanks
Miao
> 
>>
>> Looks good to me.
>>
>> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
>>
>>>
>>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
>>> ---
>>>  fs/btrfs/file-item.c    | 144
++++++++++++++++++------------------------------
>>>  fs/btrfs/ordered-data.c |  21 +++----
>>>  fs/btrfs/ordered-data.h |  25 ++-------
>>>  fs/btrfs/relocation.c   |  10 ----
>>>  fs/btrfs/scrub.c        |  16 ++----
>>>  5 files changed, 72 insertions(+), 144 deletions(-)
>>>
>>> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
>>> index 3e2f080..9a447bc 100644
>>> --- a/fs/btrfs/file-item.c
>>> +++ b/fs/btrfs/file-item.c
>>> @@ -34,8 +34,7 @@
>>>  
>>>  #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
>>>  				   sizeof(struct btrfs_ordered_sum)) / \
>>> -				   sizeof(struct btrfs_sector_sum) * \
>>> -				   (r)->sectorsize - (r)->sectorsize)
>>> +				   sizeof(u32) * (r)->sectorsize)
>>>  
>>>  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
>>>  			     struct btrfs_root *root,
>>> @@ -311,7 +310,6 @@ int btrfs_lookup_csums_range(struct btrfs_root
*root, u64 start, u64 end,
>>>  	struct btrfs_path *path;
>>>  	struct extent_buffer *leaf;
>>>  	struct btrfs_ordered_sum *sums;
>>> -	struct btrfs_sector_sum *sector_sum;
>>>  	struct btrfs_csum_item *item;
>>>  	LIST_HEAD(tmplist);
>>>  	unsigned long offset;
>>> @@ -385,34 +383,28 @@ int btrfs_lookup_csums_range(struct
btrfs_root *root, u64 start, u64 end,
>>>  				      struct btrfs_csum_item);
>>>  		while (start < csum_end) {
>>>  			size = min_t(size_t, csum_end - start,
>>> -					MAX_ORDERED_SUM_BYTES(root));
>>> +				     MAX_ORDERED_SUM_BYTES(root));
>>>  			sums = kzalloc(btrfs_ordered_sum_size(root, size),
>>> -					GFP_NOFS);
>>> +				       GFP_NOFS);
>>>  			if (!sums) {
>>>  				ret = -ENOMEM;
>>>  				goto fail;
>>>  			}
>>>  
>>> -			sector_sum = sums->sums;
>>>  			sums->bytenr = start;
>>> -			sums->len = size;
>>> +			sums->len = (int)size;
>>>  
>>>  			offset = (start - key.offset) >>
>>>  				root->fs_info->sb->s_blocksize_bits;
>>>  			offset *= csum_size;
>>> +			size >>= root->fs_info->sb->s_blocksize_bits;
>>>  
>>> -			while (size > 0) {
>>> -				read_extent_buffer(path->nodes[0],
>>> -						&sector_sum->sum,
>>> -						((unsigned long)item) +
>>> -						offset, csum_size);
>>> -				sector_sum->bytenr = start;
>>> -
>>> -				size -= root->sectorsize;
>>> -				start += root->sectorsize;
>>> -				offset += csum_size;
>>> -				sector_sum++;
>>> -			}
>>> +			read_extent_buffer(path->nodes[0],
>>> +					   sums->sums,
>>> +					   ((unsigned long)item) + offset,
>>> +					   csum_size * size);
>>> +
>>> +			start += root->sectorsize * size;
>>>  			list_add_tail(&sums->list, &tmplist);
>>>  		}
>>>  		path->slots[0]++;
>>> @@ -434,23 +426,20 @@ int btrfs_csum_one_bio(struct btrfs_root
*root, struct inode *inode,
>>>  		       struct bio *bio, u64 file_start, int contig)
>>>  {
>>>  	struct btrfs_ordered_sum *sums;
>>> -	struct btrfs_sector_sum *sector_sum;
>>>  	struct btrfs_ordered_extent *ordered;
>>>  	char *data;
>>>  	struct bio_vec *bvec = bio->bi_io_vec;
>>>  	int bio_index = 0;
>>> +	int index;
>>>  	unsigned long total_bytes = 0;
>>>  	unsigned long this_sum_bytes = 0;
>>>  	u64 offset;
>>> -	u64 disk_bytenr;
>>>  
>>>  	WARN_ON(bio->bi_vcnt <= 0);
>>>  	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size),
GFP_NOFS);
>>>  	if (!sums)
>>>  		return -ENOMEM;
>>>  
>>> -	sector_sum = sums->sums;
>>> -	disk_bytenr = (u64)bio->bi_sector << 9;
>>>  	sums->len = bio->bi_size;
>>>  	INIT_LIST_HEAD(&sums->list);
>>>  
>>> @@ -461,7 +450,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
>>>  
>>>  	ordered = btrfs_lookup_ordered_extent(inode, offset);
>>>  	BUG_ON(!ordered); /* Logic error */
>>> -	sums->bytenr = ordered->start;
>>> +	sums->bytenr = (u64)bio->bi_sector << 9;
>>> +	index = 0;
>>>  
>>>  	while (bio_index < bio->bi_vcnt) {
>>>  		if (!contig)
>>> @@ -480,29 +470,28 @@ int btrfs_csum_one_bio(struct btrfs_root
*root, struct inode *inode,
>>>  			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
>>>  				       GFP_NOFS);
>>>  			BUG_ON(!sums); /* -ENOMEM */
>>> -			sector_sum = sums->sums;
>>>  			sums->len = bytes_left;
>>>  			ordered = btrfs_lookup_ordered_extent(inode, offset);
>>>  			BUG_ON(!ordered); /* Logic error */
>>> -			sums->bytenr = ordered->start;
>>> +			sums->bytenr = ((u64)bio->bi_sector << 9) +
>>> +				       total_bytes;
>>> +			index = 0;
>>>  		}
>>>  
>>>  		data = kmap_atomic(bvec->bv_page);
>>> -		sector_sum->sum = ~(u32)0;
>>> -		sector_sum->sum = btrfs_csum_data(root,
>>> -						  data + bvec->bv_offset,
>>> -						  sector_sum->sum,
>>> -						  bvec->bv_len);
>>> +		sums->sums[index] = ~(u32)0;
>>> +		sums->sums[index] = btrfs_csum_data(root,
>>> +						    data + bvec->bv_offset,
>>> +						    sums->sums[index],
>>> +						    bvec->bv_len);
>>>  		kunmap_atomic(data);
>>> -		btrfs_csum_final(sector_sum->sum,
>>> -				 (char *)&sector_sum->sum);
>>> -		sector_sum->bytenr = disk_bytenr;
>>> +		btrfs_csum_final(sums->sums[index],
>>> +				 (char *)(sums->sums + index));
>>>  
>>> -		sector_sum++;
>>>  		bio_index++;
>>> +		index++;
>>>  		total_bytes += bvec->bv_len;
>>>  		this_sum_bytes += bvec->bv_len;
>>> -		disk_bytenr += bvec->bv_len;
>>>  		offset += bvec->bv_len;
>>>  		bvec++;
>>>  	}
>>> @@ -691,63 +680,42 @@ out:
>>>  	return ret;
>>>  }
>>>  
>>> -static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
>>> -				 struct btrfs_sector_sum *sector_sum,
>>> -				 u64 total_bytes, u64 sectorsize)
>>> -{
>>> -	u64 tmp = sectorsize;
>>> -	u64 next_sector = sector_sum->bytenr;
>>> -	struct btrfs_sector_sum *next = sector_sum + 1;
>>> -
>>> -	while ((tmp + total_bytes) < sums->len) {
>>> -		if (next_sector + sectorsize != next->bytenr)
>>> -			break;
>>> -		tmp += sectorsize;
>>> -		next_sector = next->bytenr;
>>> -		next++;
>>> -	}
>>> -	return tmp;
>>> -}
>>> -
>>>  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
>>>  			   struct btrfs_root *root,
>>>  			   struct btrfs_ordered_sum *sums)
>>>  {
>>> -	u64 bytenr;
>>> -	int ret;
>>>  	struct btrfs_key file_key;
>>>  	struct btrfs_key found_key;
>>> -	u64 next_offset;
>>> -	u64 total_bytes = 0;
>>> -	int found_next;
>>>  	struct btrfs_path *path;
>>>  	struct btrfs_csum_item *item;
>>>  	struct btrfs_csum_item *item_end;
>>>  	struct extent_buffer *leaf = NULL;
>>> +	u64 next_offset;
>>> +	u64 total_bytes = 0;
>>>  	u64 csum_offset;
>>> -	struct btrfs_sector_sum *sector_sum;
>>> +	u64 bytenr;
>>>  	u32 nritems;
>>>  	u32 ins_size;
>>> +	int index = 0;
>>> +	int found_next;
>>> +	int ret;
>>>  	u16 csum_size =
btrfs_super_csum_size(root->fs_info->super_copy);
>>>  
>>>  	path = btrfs_alloc_path();
>>>  	if (!path)
>>>  		return -ENOMEM;
>>> -
>>> -	sector_sum = sums->sums;
>>>  again:
>>>  	next_offset = (u64)-1;
>>>  	found_next = 0;
>>> +	bytenr = sums->bytenr + total_bytes;
>>>  	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
>>> -	file_key.offset = sector_sum->bytenr;
>>> -	bytenr = sector_sum->bytenr;
>>> +	file_key.offset = bytenr;
>>>  	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
>>>  
>>> -	item = btrfs_lookup_csum(trans, root, path,
sector_sum->bytenr, 1);
>>> +	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
>>>  	if (!IS_ERR(item)) {
>>> -		leaf = path->nodes[0];
>>> -		ret = 0;
>>> -		goto found;
>>> +		csum_offset = 0;
>>> +		goto csum;
>>>  	}
>>>  	ret = PTR_ERR(item);
>>>  	if (ret != -EFBIG && ret != -ENOENT)
>>> @@ -826,8 +794,7 @@ again:
>>>  
>>>  		free_space = btrfs_leaf_free_space(root, leaf) -
>>>  					 sizeof(struct btrfs_item) - csum_size;
>>> -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
>>> -					    root->sectorsize);
>>> +		tmp = sums->len - total_bytes;
>>>  		tmp >>= root->fs_info->sb->s_blocksize_bits;
>>>  		WARN_ON(tmp < 1);
>>>  
>>> @@ -850,8 +817,7 @@ insert:
>>>  	if (found_next) {
>>>  		u64 tmp;
>>>  
>>> -		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
>>> -					    root->sectorsize);
>>> +		tmp = sums->len - total_bytes;
>>>  		tmp >>= root->fs_info->sb->s_blocksize_bits;
>>>  		tmp = min(tmp, (next_offset - file_key.offset) >>
>>>  					 root->fs_info->sb->s_blocksize_bits);
>>> @@ -873,30 +839,26 @@ insert:
>>>  		goto fail_unlock;
>>>  	}
>>>  csum:
>>> +	ret = 0;
>>>  	leaf = path->nodes[0];
>>> +
>>>  	item = btrfs_item_ptr(leaf, path->slots[0], struct
btrfs_csum_item);
>>> -	ret = 0;
>>> +	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
>>> +				      btrfs_item_size_nr(leaf, path->slots[0]));
>>>  	item = (struct btrfs_csum_item *)((unsigned char *)item +
>>>  					  csum_offset * csum_size);
>>> -found:
>>> -	item_end = btrfs_item_ptr(leaf, path->slots[0], struct
btrfs_csum_item);
>>> -	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
>>> -				      btrfs_item_size_nr(leaf, path->slots[0]));
>>> -next_sector:
>>>  
>>> -	write_extent_buffer(leaf, &sector_sum->sum, (unsigned
long)item, csum_size);
>>> -
>>> -	total_bytes += root->sectorsize;
>>> -	sector_sum++;
>>> -	if (total_bytes < sums->len) {
>>> -		item = (struct btrfs_csum_item *)((char *)item +
>>> -						  csum_size);
>>> -		if (item < item_end && bytenr + PAGE_CACHE_SIZE
=>>> -		    sector_sum->bytenr) {
>>> -			bytenr = sector_sum->bytenr;
>>> -			goto next_sector;
>>> -		}
>>> -	}
>>> +	ins_size = (u32)(sums->len - total_bytes) >>
>>> +		   root->fs_info->sb->s_blocksize_bits;
>>> +	ins_size *= csum_size;
>>> +	ins_size = min_t(u32, (unsigned long)item_end - (unsigned
long)item,
>>> +			      ins_size);
>>> +	write_extent_buffer(leaf, sums->sums + index, (unsigned
long)item,
>>> +			    ins_size);
>>> +
>>> +	ins_size /= csum_size;
>>> +	total_bytes += ins_size * root->sectorsize;
>>> +	index += ins_size;
>>>  
>>>  	btrfs_mark_buffer_dirty(path->nodes[0]);
>>>  	if (total_bytes < sums->len) {
>>> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
>>> index 2b959b6..23bb43a 100644
>>> --- a/fs/btrfs/ordered-data.c
>>> +++ b/fs/btrfs/ordered-data.c
>>> @@ -987,7 +987,6 @@ int btrfs_find_ordered_sum(struct inode *inode,
u64 offset, u64 disk_bytenr,
>>>  			   u32 *sum, int len)
>>>  {
>>>  	struct btrfs_ordered_sum *ordered_sum;
>>> -	struct btrfs_sector_sum *sector_sums;
>>>  	struct btrfs_ordered_extent *ordered;
>>>  	struct btrfs_ordered_inode_tree *tree =
&BTRFS_I(inode)->ordered_tree;
>>>  	unsigned long num_sectors;
>>> @@ -1004,17 +1003,15 @@ int btrfs_find_ordered_sum(struct inode
*inode, u64 offset, u64 disk_bytenr,
>>>  		if (disk_bytenr >= ordered_sum->bytenr &&
>>>  		    disk_bytenr < ordered_sum->bytenr +
ordered_sum->len) {
>>>  			i = (disk_bytenr - ordered_sum->bytenr) / sectorsize;
>>> -			sector_sums = ordered_sum->sums + i;
>>> -			num_sectors = ordered_sum->len / sectorsize;
>>> -			for (; i < num_sectors; i++) {
>>> -				if (sector_sums[i].bytenr == disk_bytenr) {
>>> -					sum[index] = sector_sums[i].sum;
>>> -					index++;
>>> -					if (index == len)
>>> -						goto out;
>>> -					disk_bytenr += sectorsize;
>>> -				}
>>> -			}
>>> +			num_sectors = ordered_sum->len / sectorsize - i;
>>> +			num_sectors = min_t(int, len - index, num_sectors);
>>> +			memcpy(sum + index, ordered_sum->sums + i,
>>> +			       num_sectors);
>>> +
>>> +			index += (int)num_sectors;
>>> +			if (index == len)
>>> +				goto out;
>>> +			disk_bytenr += num_sectors * sectorsize;
>>>  		}
>>>  	}
>>>  out:
>>> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
>>> index 58b0e3b..888bcbb 100644
>>> --- a/fs/btrfs/ordered-data.h
>>> +++ b/fs/btrfs/ordered-data.h
>>> @@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
>>>  	struct rb_node *last;
>>>  };
>>>  
>>> -/*
>>> - * these are used to collect checksums done just before bios
submission.
>>> - * They are attached via a list into the ordered extent, and
>>> - * checksum items are inserted into the tree after all the blocks
in
>>> - * the ordered extent are on disk
>>> - */
>>> -struct btrfs_sector_sum {
>>> -	/* bytenr on disk */
>>> -	u64 bytenr;
>>> -	u32 sum;
>>> -};
>>> -
>>>  struct btrfs_ordered_sum {
>>>  	/* bytenr is the start of this extent on disk */
>>>  	u64 bytenr;
>>> @@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
>>>  	/*
>>>  	 * this is the length in bytes covered by the sums array below.
>>>  	 */
>>> -	unsigned long len;
>>> +	int len;
>>>  	struct list_head list;
>>> -	/* last field is a variable length array of btrfs_sector_sums */
>>> -	struct btrfs_sector_sum sums[];
>>> +	/* last field is a variable length array of csums */
>>> +	u32 sums[];
>>>  };
>>>  
>>>  /*
>>> @@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
>>>  static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
>>>  					 unsigned long bytes)
>>>  {
>>> -	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
>>> -		root->sectorsize;
>>> -	num_sectors++;
>>> -	return sizeof(struct btrfs_ordered_sum) +
>>> -		num_sectors * sizeof(struct btrfs_sector_sum);
>>> +	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
>>> +	return sizeof(struct btrfs_ordered_sum) + num_sectors *
sizeof(u32);
>>>  }
>>>  
>>>  static inline void
>>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
>>> index 3ebe879..5928142 100644
>>> --- a/fs/btrfs/relocation.c
>>> +++ b/fs/btrfs/relocation.c
>>> @@ -4335,10 +4335,8 @@ out:
>>>  int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64
len)
>>>  {
>>>  	struct btrfs_ordered_sum *sums;
>>> -	struct btrfs_sector_sum *sector_sum;
>>>  	struct btrfs_ordered_extent *ordered;
>>>  	struct btrfs_root *root = BTRFS_I(inode)->root;
>>> -	size_t offset;
>>>  	int ret;
>>>  	u64 disk_bytenr;
>>>  	LIST_HEAD(list);
>>> @@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode
*inode, u64 file_pos, u64 len)
>>>  		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
>>>  		list_del_init(&sums->list);
>>>  
>>> -		sector_sum = sums->sums;
>>>  		sums->bytenr = ordered->start;
>>>  
>>> -		offset = 0;
>>> -		while (offset < sums->len) {
>>> -			sector_sum->bytenr += ordered->start - disk_bytenr;
>>> -			sector_sum++;
>>> -			offset += root->sectorsize;
>>> -		}
>>> -
>>>  		btrfs_add_ordered_sum(inode, ordered, sums);
>>>  	}
>>>  out:
>>> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
>>> index 53c3501..6c292b1 100644
>>> --- a/fs/btrfs/scrub.c
>>> +++ b/fs/btrfs/scrub.c
>>> @@ -2128,8 +2128,7 @@ static int scrub_find_csum(struct scrub_ctx
*sctx, u64 logical, u64 len,
>>>  			   u8 *csum)
>>>  {
>>>  	struct btrfs_ordered_sum *sum = NULL;
>>> -	int ret = 0;
>>> -	unsigned long i;
>>> +	unsigned long index;
>>>  	unsigned long num_sectors;
>>>  
>>>  	while (!list_empty(&sctx->csum_list)) {
>>> @@ -2148,19 +2147,14 @@ static int scrub_find_csum(struct scrub_ctx
*sctx, u64 logical, u64 len,
>>>  	if (!sum)
>>>  		return 0;
>>>  
>>> +	index = (logical - sum->bytenr) / sctx->sectorsize;
>>>  	num_sectors = sum->len / sctx->sectorsize;
>>> -	for (i = 0; i < num_sectors; ++i) {
>>> -		if (sum->sums[i].bytenr == logical) {
>>> -			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
>>> -			ret = 1;
>>> -			break;
>>> -		}
>>> -	}
>>> -	if (ret && i == num_sectors - 1) {
>>> +	memcpy(csum, sum->sums + index, sctx->csum_size);
>>> +	if (index == num_sectors - 1) {
>>>  		list_del(&sum->list);
>>>  		kfree(sum);
>>>  	}
>>> -	return ret;
>>> +	return 1;
>>>  }
>>>  
>>>  /* scrub extent tries to collect up to 64 kB for each bio */
>>> -- 
>>> 1.8.0.1
>>> --
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Using the structure btrfs_sector_sum to keep the checksum value is
unnecessary, because the extents that btrfs_sector_sum points to are
continuous, we can find out the expected checksums by
btrfs_ordered_sum''s
bytenr and the offset, so we can remove btrfs_sector_sum''s bytenr.
After
removing bytenr, there is only one member in the structure, so it makes
no sense to keep the structure, just remove it, and use a u32 array to
store the checksum value.

By this change, we don''t use the while loop to get the checksums one by
one. Now, we can get several checksum value at one time, it improved the
performance by ~74% on my SSD (31MB/s -> 54MB/s).

test command:
 # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
---
Changelog v1 -> v2:
- modify the changelog and the title which can not explain this patch clearly
- fix the 64bit division problem on 32bit machine
---
 fs/btrfs/file-item.c    | 144 ++++++++++++++++++------------------------------
 fs/btrfs/ordered-data.c |  19 +++----
 fs/btrfs/ordered-data.h |  25 ++-------
 fs/btrfs/relocation.c   |  10 ----
 fs/btrfs/scrub.c        |  16 ++----
 5 files changed, 71 insertions(+), 143 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 484017a..8d653c2 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -34,8 +34,7 @@
 
 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
 				   sizeof(struct btrfs_ordered_sum)) / \
-				   sizeof(struct btrfs_sector_sum) * \
-				   (r)->sectorsize - (r)->sectorsize)
+				   sizeof(u32) * (r)->sectorsize)
 
 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
@@ -313,7 +312,6 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_csum_item *item;
 	LIST_HEAD(tmplist);
 	unsigned long offset;
@@ -387,34 +385,28 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64
start, u64 end,
 				      struct btrfs_csum_item);
 		while (start < csum_end) {
 			size = min_t(size_t, csum_end - start,
-					MAX_ORDERED_SUM_BYTES(root));
+				     MAX_ORDERED_SUM_BYTES(root));
 			sums = kzalloc(btrfs_ordered_sum_size(root, size),
-					GFP_NOFS);
+				       GFP_NOFS);
 			if (!sums) {
 				ret = -ENOMEM;
 				goto fail;
 			}
 
-			sector_sum = sums->sums;
 			sums->bytenr = start;
-			sums->len = size;
+			sums->len = (int)size;
 
 			offset = (start - key.offset) >>
 				root->fs_info->sb->s_blocksize_bits;
 			offset *= csum_size;
+			size >>= root->fs_info->sb->s_blocksize_bits;
 
-			while (size > 0) {
-				read_extent_buffer(path->nodes[0],
-						&sector_sum->sum,
-						((unsigned long)item) +
-						offset, csum_size);
-				sector_sum->bytenr = start;
-
-				size -= root->sectorsize;
-				start += root->sectorsize;
-				offset += csum_size;
-				sector_sum++;
-			}
+			read_extent_buffer(path->nodes[0],
+					   sums->sums,
+					   ((unsigned long)item) + offset,
+					   csum_size * size);
+
+			start += root->sectorsize * size;
 			list_add_tail(&sums->list, &tmplist);
 		}
 		path->slots[0]++;
@@ -436,23 +428,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 		       struct bio *bio, u64 file_start, int contig)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	char *data;
 	struct bio_vec *bvec = bio->bi_io_vec;
 	int bio_index = 0;
+	int index;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
 	u64 offset;
-	u64 disk_bytenr;
 
 	WARN_ON(bio->bi_vcnt <= 0);
 	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 	if (!sums)
 		return -ENOMEM;
 
-	sector_sum = sums->sums;
-	disk_bytenr = (u64)bio->bi_sector << 9;
 	sums->len = bio->bi_size;
 	INIT_LIST_HEAD(&sums->list);
 
@@ -463,7 +452,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode
*inode,
 
 	ordered = btrfs_lookup_ordered_extent(inode, offset);
 	BUG_ON(!ordered); /* Logic error */
-	sums->bytenr = ordered->start;
+	sums->bytenr = (u64)bio->bi_sector << 9;
+	index = 0;
 
 	while (bio_index < bio->bi_vcnt) {
 		if (!contig)
@@ -482,29 +472,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
 			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 				       GFP_NOFS);
 			BUG_ON(!sums); /* -ENOMEM */
-			sector_sum = sums->sums;
 			sums->len = bytes_left;
 			ordered = btrfs_lookup_ordered_extent(inode, offset);
 			BUG_ON(!ordered); /* Logic error */
-			sums->bytenr = ordered->start;
+			sums->bytenr = ((u64)bio->bi_sector << 9) +
+				       total_bytes;
+			index = 0;
 		}
 
 		data = kmap_atomic(bvec->bv_page);
-		sector_sum->sum = ~(u32)0;
-		sector_sum->sum = btrfs_csum_data(root,
-						  data + bvec->bv_offset,
-						  sector_sum->sum,
-						  bvec->bv_len);
+		sums->sums[index] = ~(u32)0;
+		sums->sums[index] = btrfs_csum_data(root,
+						    data + bvec->bv_offset,
+						    sums->sums[index],
+						    bvec->bv_len);
 		kunmap_atomic(data);
-		btrfs_csum_final(sector_sum->sum,
-				 (char *)&sector_sum->sum);
-		sector_sum->bytenr = disk_bytenr;
+		btrfs_csum_final(sums->sums[index],
+				 (char *)(sums->sums + index));
 
-		sector_sum++;
 		bio_index++;
+		index++;
 		total_bytes += bvec->bv_len;
 		this_sum_bytes += bvec->bv_len;
-		disk_bytenr += bvec->bv_len;
 		offset += bvec->bv_len;
 		bvec++;
 	}
@@ -693,63 +682,42 @@ out:
 	return ret;
 }
 
-static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
-				 struct btrfs_sector_sum *sector_sum,
-				 u64 total_bytes, u64 sectorsize)
-{
-	u64 tmp = sectorsize;
-	u64 next_sector = sector_sum->bytenr;
-	struct btrfs_sector_sum *next = sector_sum + 1;
-
-	while ((tmp + total_bytes) < sums->len) {
-		if (next_sector + sectorsize != next->bytenr)
-			break;
-		tmp += sectorsize;
-		next_sector = next->bytenr;
-		next++;
-	}
-	return tmp;
-}
-
 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums)
 {
-	u64 bytenr;
-	int ret;
 	struct btrfs_key file_key;
 	struct btrfs_key found_key;
-	u64 next_offset;
-	u64 total_bytes = 0;
-	int found_next;
 	struct btrfs_path *path;
 	struct btrfs_csum_item *item;
 	struct btrfs_csum_item *item_end;
 	struct extent_buffer *leaf = NULL;
+	u64 next_offset;
+	u64 total_bytes = 0;
 	u64 csum_offset;
-	struct btrfs_sector_sum *sector_sum;
+	u64 bytenr;
 	u32 nritems;
 	u32 ins_size;
+	int index = 0;
+	int found_next;
+	int ret;
 	u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
-
-	sector_sum = sums->sums;
 again:
 	next_offset = (u64)-1;
 	found_next = 0;
+	bytenr = sums->bytenr + total_bytes;
 	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-	file_key.offset = sector_sum->bytenr;
-	bytenr = sector_sum->bytenr;
+	file_key.offset = bytenr;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 
-	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
+	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
 	if (!IS_ERR(item)) {
-		leaf = path->nodes[0];
-		ret = 0;
-		goto found;
+		csum_offset = 0;
+		goto csum;
 	}
 	ret = PTR_ERR(item);
 	if (ret != -EFBIG && ret != -ENOENT)
@@ -828,8 +796,7 @@ again:
 
 		free_space = btrfs_leaf_free_space(root, leaf) -
 					 sizeof(struct btrfs_item) - csum_size;
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		WARN_ON(tmp < 1);
 
@@ -852,8 +819,7 @@ insert:
 	if (found_next) {
 		u64 tmp;
 
-		tmp = btrfs_sector_sum_left(sums, sector_sum, total_bytes,
-					    root->sectorsize);
+		tmp = sums->len - total_bytes;
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		tmp = min(tmp, (next_offset - file_key.offset) >>
 					 root->fs_info->sb->s_blocksize_bits);
@@ -875,30 +841,26 @@ insert:
 		goto fail_unlock;
 	}
 csum:
+	ret = 0;
 	leaf = path->nodes[0];
+
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	ret = 0;
+	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
+				      btrfs_item_size_nr(leaf, path->slots[0]));
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
-found:
-	item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
-	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
-				      btrfs_item_size_nr(leaf, path->slots[0]));
-next_sector:
 
-	write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item,
csum_size);
-
-	total_bytes += root->sectorsize;
-	sector_sum++;
-	if (total_bytes < sums->len) {
-		item = (struct btrfs_csum_item *)((char *)item +
-						  csum_size);
-		if (item < item_end && bytenr + PAGE_CACHE_SIZE =-		   
sector_sum->bytenr) {
-			bytenr = sector_sum->bytenr;
-			goto next_sector;
-		}
-	}
+	ins_size = (u32)(sums->len - total_bytes) >>
+		   root->fs_info->sb->s_blocksize_bits;
+	ins_size *= csum_size;
+	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
+			      ins_size);
+	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
+			    ins_size);
+
+	ins_size /= csum_size;
+	total_bytes += ins_size * root->sectorsize;
+	index += ins_size;
 
 	btrfs_mark_buffer_dirty(path->nodes[0]);
 	if (total_bytes < sums->len) {
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 1ddd728..937c40c 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -989,7 +989,6 @@ int btrfs_find_ordered_sum(struct inode *inode, u64 offset,
u64 disk_bytenr,
 			   u32 *sum, int len)
 {
 	struct btrfs_ordered_sum *ordered_sum;
-	struct btrfs_sector_sum *sector_sums;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 	unsigned long num_sectors;
@@ -1007,18 +1006,16 @@ int btrfs_find_ordered_sum(struct inode *inode, u64
offset, u64 disk_bytenr,
 		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len) {
 			i = (disk_bytenr - ordered_sum->bytenr) >>
 			    inode->i_sb->s_blocksize_bits;
-			sector_sums = ordered_sum->sums + i;
 			num_sectors = ordered_sum->len >>
 				      inode->i_sb->s_blocksize_bits;
-			for (; i < num_sectors; i++) {
-				if (sector_sums[i].bytenr == disk_bytenr) {
-					sum[index] = sector_sums[i].sum;
-					index++;
-					if (index == len)
-						goto out;
-					disk_bytenr += sectorsize;
-				}
-			}
+			num_sectors = min_t(int, len - index, num_sectors - i);
+			memcpy(sum + index, ordered_sum->sums + i,
+			       num_sectors);
+
+			index += (int)num_sectors;
+			if (index == len)
+				goto out;
+			disk_bytenr += num_sectors * sectorsize;
 		}
 	}
 out:
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 58b0e3b..888bcbb 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -26,18 +26,6 @@ struct btrfs_ordered_inode_tree {
 	struct rb_node *last;
 };
 
-/*
- * these are used to collect checksums done just before bios submission.
- * They are attached via a list into the ordered extent, and
- * checksum items are inserted into the tree after all the blocks in
- * the ordered extent are on disk
- */
-struct btrfs_sector_sum {
-	/* bytenr on disk */
-	u64 bytenr;
-	u32 sum;
-};
-
 struct btrfs_ordered_sum {
 	/* bytenr is the start of this extent on disk */
 	u64 bytenr;
@@ -45,10 +33,10 @@ struct btrfs_ordered_sum {
 	/*
 	 * this is the length in bytes covered by the sums array below.
 	 */
-	unsigned long len;
+	int len;
 	struct list_head list;
-	/* last field is a variable length array of btrfs_sector_sums */
-	struct btrfs_sector_sum sums[];
+	/* last field is a variable length array of csums */
+	u32 sums[];
 };
 
 /*
@@ -149,11 +137,8 @@ struct btrfs_ordered_extent {
 static inline int btrfs_ordered_sum_size(struct btrfs_root *root,
 					 unsigned long bytes)
 {
-	unsigned long num_sectors = (bytes + root->sectorsize - 1) /
-		root->sectorsize;
-	num_sectors++;
-	return sizeof(struct btrfs_ordered_sum) +
-		num_sectors * sizeof(struct btrfs_sector_sum);
+	int num_sectors = (int)DIV_ROUND_UP(bytes, root->sectorsize);
+	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
 }
 
 static inline void
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3ebe879..5928142 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4335,10 +4335,8 @@ out:
 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 {
 	struct btrfs_ordered_sum *sums;
-	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	size_t offset;
 	int ret;
 	u64 disk_bytenr;
 	LIST_HEAD(list);
@@ -4356,16 +4354,8 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64
file_pos, u64 len)
 		sums = list_entry(list.next, struct btrfs_ordered_sum, list);
 		list_del_init(&sums->list);
 
-		sector_sum = sums->sums;
 		sums->bytenr = ordered->start;
 
-		offset = 0;
-		while (offset < sums->len) {
-			sector_sum->bytenr += ordered->start - disk_bytenr;
-			sector_sum++;
-			offset += root->sectorsize;
-		}
-
 		btrfs_add_ordered_sum(inode, ordered, sums);
 	}
 out:
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 85e072b..9a81e65 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2129,8 +2129,7 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 			   u8 *csum)
 {
 	struct btrfs_ordered_sum *sum = NULL;
-	int ret = 0;
-	unsigned long i;
+	unsigned long index;
 	unsigned long num_sectors;
 
 	while (!list_empty(&sctx->csum_list)) {
@@ -2149,19 +2148,14 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
logical, u64 len,
 	if (!sum)
 		return 0;
 
+	index = ((u32)(logical - sum->bytenr)) / sctx->sectorsize;
 	num_sectors = sum->len / sctx->sectorsize;
-	for (i = 0; i < num_sectors; ++i) {
-		if (sum->sums[i].bytenr == logical) {
-			memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
-			ret = 1;
-			break;
-		}
-	}
-	if (ret && i == num_sectors - 1) {
+	memcpy(csum, sum->sums + index, sctx->csum_size);
+	if (index == num_sectors - 1) {
 		list_del(&sum->list);
 		kfree(sum);
 	}
-	return ret;
+	return 1;
 }
 
 /* scrub extent tries to collect up to 64 kB for each bio */
-- 
1.8.0.1

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On Wed, Apr 03, 2013 at 03:14:56AM -0600, Miao Xie
wrote:
> Using the structure btrfs_sector_sum to keep the checksum value is
> unnecessary, because the extents that btrfs_sector_sum points to are
> continuous, we can find out the expected checksums by
btrfs_ordered_sum''s
> bytenr and the offset, so we can remove btrfs_sector_sum''s bytenr.
After
> removing bytenr, there is only one member in the structure, so it makes
> no sense to keep the structure, just remove it, and use a u32 array to
> store the checksum value.
> 
> By this change, we don''t use the while loop to get the checksums
one by
> one. Now, we can get several checksum value at one time, it improved the
> performance by ~74% on my SSD (31MB/s -> 54MB/s).
> 
> test command:
>  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
> 
> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> ---
> Changelog v1 -> v2:
> - modify the changelog and the title which can not explain this patch
clearly
> - fix the 64bit division problem on 32bit machine
> ---
>  fs/btrfs/file-item.c    | 144
++++++++++++++++++------------------------------
>  fs/btrfs/ordered-data.c |  19 +++----
>  fs/btrfs/ordered-data.h |  25 ++-------
>  fs/btrfs/relocation.c   |  10 ----
>  fs/btrfs/scrub.c        |  16 ++----
>  5 files changed, 71 insertions(+), 143 deletions(-)
> 
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index 484017a..8d653c2 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -34,8 +34,7 @@
> 
>  #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
>                                    sizeof(struct btrfs_ordered_sum)) / \
> -                                  sizeof(struct btrfs_sector_sum) * \
> -                                  (r)->sectorsize - (r)->sectorsize)
> +                                  sizeof(u32) * (r)->sectorsize)
> 
>  int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
>                              struct btrfs_root *root,
> @@ -313,7 +312,6 @@ int btrfs_lookup_csums_range(struct btrfs_root *root,
u64 start, u64 end,
>         struct btrfs_path *path;
>         struct extent_buffer *leaf;
>         struct btrfs_ordered_sum *sums;
> -       struct btrfs_sector_sum *sector_sum;
>         struct btrfs_csum_item *item;
>         LIST_HEAD(tmplist);
>         unsigned long offset;
> @@ -387,34 +385,28 @@ int btrfs_lookup_csums_range(struct btrfs_root *root,
u64 start, u64 end,
>                                       struct btrfs_csum_item);
>                 while (start < csum_end) {
>                         size = min_t(size_t, csum_end - start,
> -                                       MAX_ORDERED_SUM_BYTES(root));
> +                                    MAX_ORDERED_SUM_BYTES(root));
>                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
> -                                       GFP_NOFS);
> +                                      GFP_NOFS);
>                         if (!sums) {
>                                 ret = -ENOMEM;
>                                 goto fail;
>                         }
> 
> -                       sector_sum = sums->sums;
>                         sums->bytenr = start;
> -                       sums->len = size;
> +                       sums->len = (int)size;
> 
>                         offset = (start - key.offset) >>
>                                
root->fs_info->sb->s_blocksize_bits;
>                         offset *= csum_size;
> +                       size >>=
root->fs_info->sb->s_blocksize_bits;
> 
> -                       while (size > 0) {
> -                               read_extent_buffer(path->nodes[0],
> -                                               &sector_sum->sum,
> -                                               ((unsigned long)item) +
> -                                               offset, csum_size);
> -                               sector_sum->bytenr = start;
> -
> -                               size -= root->sectorsize;
> -                               start += root->sectorsize;
> -                               offset += csum_size;
> -                               sector_sum++;
> -                       }
> +                       read_extent_buffer(path->nodes[0],
> +                                          sums->sums,
> +                                          ((unsigned long)item) + offset,
> +                                          csum_size * size);
> +
> +                       start += root->sectorsize * size;
>                         list_add_tail(&sums->list, &tmplist);
>                 }
>                 path->slots[0]++;
> @@ -436,23 +428,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
>                        struct bio *bio, u64 file_start, int contig)
>  {
>         struct btrfs_ordered_sum *sums;
> -       struct btrfs_sector_sum *sector_sum;
>         struct btrfs_ordered_extent *ordered;
>         char *data;
>         struct bio_vec *bvec = bio->bi_io_vec;
>         int bio_index = 0;
> +       int index;
>         unsigned long total_bytes = 0;
>         unsigned long this_sum_bytes = 0;
>         u64 offset;
> -       u64 disk_bytenr;
> 
>         WARN_ON(bio->bi_vcnt <= 0);
>         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size),
GFP_NOFS);
>         if (!sums)
>                 return -ENOMEM;
> 
> -       sector_sum = sums->sums;
> -       disk_bytenr = (u64)bio->bi_sector << 9;
>         sums->len = bio->bi_size;
>         INIT_LIST_HEAD(&sums->list);
> 
> @@ -463,7 +452,8 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct
inode *inode,
> 
>         ordered = btrfs_lookup_ordered_extent(inode, offset);
>         BUG_ON(!ordered); /* Logic error */
> -       sums->bytenr = ordered->start;
> +       sums->bytenr = (u64)bio->bi_sector << 9;
> +       index = 0;
> 
>         while (bio_index < bio->bi_vcnt) {
>                 if (!contig)
> @@ -482,29 +472,28 @@ int btrfs_csum_one_bio(struct btrfs_root *root,
struct inode *inode,
>                         sums = kzalloc(btrfs_ordered_sum_size(root,
bytes_left),
>                                        GFP_NOFS);
>                         BUG_ON(!sums); /* -ENOMEM */
> -                       sector_sum = sums->sums;
>                         sums->len = bytes_left;
>                         ordered = btrfs_lookup_ordered_extent(inode,
offset);
>                         BUG_ON(!ordered); /* Logic error */
> -                       sums->bytenr = ordered->start;
> +                       sums->bytenr = ((u64)bio->bi_sector <<
9) +
> +                                      total_bytes;
> +                       index = 0;
>                 }
> 
>                 data = kmap_atomic(bvec->bv_page);
> -               sector_sum->sum = ~(u32)0;
> -               sector_sum->sum = btrfs_csum_data(root,
> -                                                 data +
bvec->bv_offset,
> -                                                 sector_sum->sum,
> -                                                 bvec->bv_len);
> +               sums->sums[index] = ~(u32)0;
> +               sums->sums[index] = btrfs_csum_data(root,
> +                                                   data +
bvec->bv_offset,
> +                                                   sums->sums[index],
> +                                                   bvec->bv_len);
>                 kunmap_atomic(data);
> -               btrfs_csum_final(sector_sum->sum,
> -                                (char *)&sector_sum->sum);
> -               sector_sum->bytenr = disk_bytenr;
> +               btrfs_csum_final(sums->sums[index],
> +                                (char *)(sums->sums + index));
> 
> -               sector_sum++;
>                 bio_index++;
> +               index++;
>                 total_bytes += bvec->bv_len;
>                 this_sum_bytes += bvec->bv_len;
> -               disk_bytenr += bvec->bv_len;
>                 offset += bvec->bv_len;
>                 bvec++;
>         }
> @@ -693,63 +682,42 @@ out:
>         return ret;
>  }
> 
> -static u64 btrfs_sector_sum_left(struct btrfs_ordered_sum *sums,
> -                                struct btrfs_sector_sum *sector_sum,
> -                                u64 total_bytes, u64 sectorsize)
> -{
> -       u64 tmp = sectorsize;
> -       u64 next_sector = sector_sum->bytenr;
> -       struct btrfs_sector_sum *next = sector_sum + 1;
> -
> -       while ((tmp + total_bytes) < sums->len) {
> -               if (next_sector + sectorsize != next->bytenr)
> -                       break;
> -               tmp += sectorsize;
> -               next_sector = next->bytenr;
> -               next++;
> -       }
> -       return tmp;
> -}
> -
>  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
>                            struct btrfs_root *root,
>                            struct btrfs_ordered_sum *sums)
>  {
> -       u64 bytenr;
> -       int ret;
>         struct btrfs_key file_key;
>         struct btrfs_key found_key;
> -       u64 next_offset;
> -       u64 total_bytes = 0;
> -       int found_next;
>         struct btrfs_path *path;
>         struct btrfs_csum_item *item;
>         struct btrfs_csum_item *item_end;
>         struct extent_buffer *leaf = NULL;
> +       u64 next_offset;
> +       u64 total_bytes = 0;
>         u64 csum_offset;
> -       struct btrfs_sector_sum *sector_sum;
> +       u64 bytenr;
>         u32 nritems;
>         u32 ins_size;
> +       int index = 0;
> +       int found_next;
> +       int ret;
>         u16 csum_size =
btrfs_super_csum_size(root->fs_info->super_copy);
> 
>         path = btrfs_alloc_path();
>         if (!path)
>                 return -ENOMEM;
> -
> -       sector_sum = sums->sums;
>  again:
>         next_offset = (u64)-1;
>         found_next = 0;
> +       bytenr = sums->bytenr + total_bytes;
>         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
> -       file_key.offset = sector_sum->bytenr;
> -       bytenr = sector_sum->bytenr;
> +       file_key.offset = bytenr;
>         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
> 
> -       item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr,
1);
> +       item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
>         if (!IS_ERR(item)) {
> -               leaf = path->nodes[0];
> -               ret = 0;
> -               goto found;
> +               csum_offset = 0;
> +               goto csum;
Ok I''ve just spent the last 3 hours tracking down an fsync() problem
that turned
out to be because of this patch.  btrfs_lookup_csum() assumes you are just going
in 4k chunks, but we could be going in larger chunks.  So as long as the bytenr
falls inside of this csum item it thinks its good.  So what I''m seeing
is this,
we have item

[0-8k]

and we are csumming

[4k-12k]

and then we''re adding our new csum into the old one, the sizes match
but the
bytenrs don''t match.  If you want a reproducer just run my fsync
xfstest that I
just posted.  I''m dropping this patch for now and I''ll wait
for you to fix it.
Thanks,

Josef
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On tue, 23 Apr 2013 16:54:35 -0400, Josef Bacik wrote:
> On Wed, Apr 03, 2013 at 03:14:56AM -0600, Miao Xie wrote:
>> Using the structure btrfs_sector_sum to keep the checksum value is
>> unnecessary, because the extents that btrfs_sector_sum points to are
>> continuous, we can find out the expected checksums by
btrfs_ordered_sum''s
>> bytenr and the offset, so we can remove btrfs_sector_sum''s
bytenr. After
>> removing bytenr, there is only one member in the structure, so it makes
>> no sense to keep the structure, just remove it, and use a u32 array to
>> store the checksum value.
>>
>> By this change, we don''t use the while loop to get the
checksums one by
>> one. Now, we can get several checksum value at one time, it improved
the
>> performance by ~74% on my SSD (31MB/s -> 54MB/s).
>>
>> test command:
>>  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
>>
>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
>> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
[SNIP]
>>         next_offset = (u64)-1;
>>         found_next = 0;
>> +       bytenr = sums->bytenr + total_bytes;
>>         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
>> -       file_key.offset = sector_sum->bytenr;
>> -       bytenr = sector_sum->bytenr;
>> +       file_key.offset = bytenr;
>>         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
>>
>> -       item = btrfs_lookup_csum(trans, root, path,
sector_sum->bytenr, 1);
>> +       item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
>>         if (!IS_ERR(item)) {
>> -               leaf = path->nodes[0];
>> -               ret = 0;
>> -               goto found;
>> +               csum_offset = 0;
>> +               goto csum;
> 
> Ok I''ve just spent the last 3 hours tracking down an fsync()
problem that turned
> out to be because of this patch.  btrfs_lookup_csum() assumes you are just
going
> in 4k chunks, but we could be going in larger chunks.  So as long as the
bytenr
> falls inside of this csum item it thinks its good.  So what I''m
seeing is this,
> we have item
> 
> [0-8k]
> 
> and we are csumming
> 
> [4k-12k]
> 
> and then we''re adding our new csum into the old one, the sizes
match but the
> bytenrs don''t match.  If you want a reproducer just run my fsync
xfstest that I
> just posted.  I''m dropping this patch for now and I''ll
wait for you to fix it.
> Thanks,
Is the reproducer is the 311th case of xfstests?
([PATCH] xfstests 311: test fsync with dm flakey V2)

If yes, I''m so sorry that we didn''t reproduce the problem you
said above. Could you
give me your test option?

Thanks
Miao

On Fri, 26 Apr 2013 16:58:18 +0800, Miao Xie wrote:
> On tue, 23 Apr 2013 16:54:35 -0400, Josef Bacik wrote:
>> On Wed, Apr 03, 2013 at 03:14:56AM -0600, Miao Xie wrote:
>>> Using the structure btrfs_sector_sum to keep the checksum value is
>>> unnecessary, because the extents that btrfs_sector_sum points to
are
>>> continuous, we can find out the expected checksums by
btrfs_ordered_sum''s
>>> bytenr and the offset, so we can remove btrfs_sector_sum''s
bytenr. After
>>> removing bytenr, there is only one member in the structure, so it
makes
>>> no sense to keep the structure, just remove it, and use a u32 array
to
>>> store the checksum value.
>>>
>>> By this change, we don''t use the while loop to get the
checksums one by
>>> one. Now, we can get several checksum value at one time, it
improved the
>>> performance by ~74% on my SSD (31MB/s -> 54MB/s).
>>>
>>> test command:
>>>  # dd if=/dev/zero of=/mnt/btrfs/file0 bs=1M count=1024 oflag=sync
>>>
>>> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
>>> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> [SNIP]
>>>         next_offset = (u64)-1;
>>>         found_next = 0;
>>> +       bytenr = sums->bytenr + total_bytes;
>>>         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
>>> -       file_key.offset = sector_sum->bytenr;
>>> -       bytenr = sector_sum->bytenr;
>>> +       file_key.offset = bytenr;
>>>         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
>>>
>>> -       item = btrfs_lookup_csum(trans, root, path,
sector_sum->bytenr, 1);
>>> +       item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
>>>         if (!IS_ERR(item)) {
>>> -               leaf = path->nodes[0];
>>> -               ret = 0;
>>> -               goto found;
>>> +               csum_offset = 0;
>>> +               goto csum;
>>
>> Ok I''ve just spent the last 3 hours tracking down an fsync()
problem that turned
>> out to be because of this patch.  btrfs_lookup_csum() assumes you are
just going
>> in 4k chunks, but we could be going in larger chunks.  So as long as
the bytenr
>> falls inside of this csum item it thinks its good.  So what
I''m seeing is this,
>> we have item
>>
>> [0-8k]
>>
>> and we are csumming
>>
>> [4k-12k]
>>
>> and then we''re adding our new csum into the old one, the sizes
match but the
>> bytenrs don''t match.  If you want a reproducer just run my
fsync xfstest that I
>> just posted.  I''m dropping this patch for now and
I''ll wait for you to fix it.
>> Thanks,
> 
> Is the reproducer is the 311th case of xfstests?
> ([PATCH] xfstests 311: test fsync with dm flakey V2)
> 
> If yes, I''m so sorry that we didn''t reproduce the problem
you said above. Could you
> give me your test option?
please ignore the attached patch, I sent it out by mistake.

Thanks
Miao
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