jim owens
2009-Dec-17 23:29 UTC
[PATCH] Reorder __btrfs_map_block to make code more efficient.
Allocate multi structure only after we know the correct size
and do not do unneeded steps when we are only returning length.
Signed-off-by: jim owens <jowens@hp.com>
---
fs/btrfs/volumes.c | 65 +++++++++++++++++++--------------------------------
1 files changed, 24 insertions(+), 41 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e555408..db5fe6c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2625,26 +2625,12 @@ static int __btrfs_map_block(struct btrfs_mapping_tree
*map_tree, int rw,
u64 offset;
u64 stripe_offset;
u64 stripe_nr;
- int stripes_allocated = 8;
- int stripes_required = 1;
int stripe_index;
int i;
int num_stripes;
- int max_errors = 0;
+ int max_errors;
struct btrfs_multi_bio *multi = NULL;
- if (multi_ret && !(rw & (1 << BIO_RW)))
- stripes_allocated = 1;
-again:
- if (multi_ret) {
- multi = kzalloc(btrfs_multi_bio_size(stripes_allocated),
- GFP_NOFS);
- if (!multi)
- return -ENOMEM;
-
- atomic_set(&multi->error, 0);
- }
-
read_lock(&em_tree->lock);
em = lookup_extent_mapping(em_tree, logical, *length);
read_unlock(&em_tree->lock);
@@ -2663,27 +2649,6 @@ again:
map = (struct map_lookup *)em->bdev;
offset = logical - em->start;
- if (mirror_num > map->num_stripes)
- mirror_num = 0;
-
- /* if our multi bio struct is too small, back off and try again */
- if (rw & (1 << BIO_RW)) {
- if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
- BTRFS_BLOCK_GROUP_DUP)) {
- stripes_required = map->num_stripes;
- max_errors = 1;
- } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
- stripes_required = map->sub_stripes;
- max_errors = 1;
- }
- }
- if (multi_ret && (rw & (1 << BIO_RW)) &&
- stripes_allocated < stripes_required) {
- stripes_allocated = map->num_stripes;
- free_extent_map(em);
- kfree(multi);
- goto again;
- }
stripe_nr = offset;
/*
* stripe_nr counts the total number of stripes we have to stride
@@ -2711,6 +2676,18 @@ again:
if (!multi_ret && !unplug_page)
goto out;
+ if (mirror_num > map->num_stripes)
+ mirror_num = 0;
+
+ max_errors = 0;
+ if (rw & (1 << BIO_RW)) {
+ if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
+ BTRFS_BLOCK_GROUP_DUP))
+ max_errors = 1;
+ else if (map->type & BTRFS_BLOCK_GROUP_RAID10)
+ max_errors = 1;
+ }
+
num_stripes = 1;
stripe_index = 0;
if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
@@ -2755,6 +2732,17 @@ again:
}
BUG_ON(stripe_index >= map->num_stripes);
+ if (multi_ret) {
+ multi = kzalloc(btrfs_multi_bio_size(num_stripes), GFP_NOFS);
+ if (!multi)
+ return -ENOMEM;
+ *multi_ret = multi;
+
+ atomic_set(&multi->error, 0);
+ multi->num_stripes = num_stripes;
+ multi->max_errors = max_errors;
+ }
+
for (i = 0; i < num_stripes; i++) {
if (unplug_page) {
struct btrfs_device *device;
@@ -2774,11 +2762,6 @@ again:
}
stripe_index++;
}
- if (multi_ret) {
- *multi_ret = multi;
- multi->num_stripes = num_stripes;
- multi->max_errors = max_errors;
- }
out:
free_extent_map(em);
return 0;
--
1.5.6.3
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