Josef Bacik
2014-Jun-05 20:15 UTC
[PATCH] Btrfs: make fiemap not blow when you have lots of snapshots
We have been iterating all references for each extent we have in a file when we
do fiemap to see if it is shared. This is fine when you have a few clones or a
few snapshots, but when you have 5k snapshots suddenly fiemap just sits there
and stares at you. So add btrfs_check_shared which will use the backref walking
code but will short circuit as soon as it finds a root or inode that doesn't
match the one we currently have. This makes fiemap on my testbox go from
looking at me blankly for a day to spitting out actual output in a reasonable
amount of time. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
---
fs/btrfs/backref.c | 109 +++++++++++++++++++++++++++++++++++++++++++++------
fs/btrfs/backref.h | 3 ++
fs/btrfs/extent_io.c | 44 ++++++++-------------
3 files changed, 118 insertions(+), 38 deletions(-)
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 84d0912..baacc41 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -25,6 +25,9 @@
#include "delayed-ref.h"
#include "locking.h"
+/* Just an arbitrary number so we can be sure this happened */
+#define BACKREF_FOUND_SHARED 6
+
struct extent_inode_elem {
u64 inum;
u64 offset;
@@ -378,7 +381,8 @@ out:
static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 time_seq,
struct list_head *head,
- const u64 *extent_item_pos, u64 total_refs)
+ const u64 *extent_item_pos, u64 total_refs,
+ u64 root_objectid)
{
int err;
int ret = 0;
@@ -403,6 +407,10 @@ static int __resolve_indirect_refs(struct btrfs_fs_info
*fs_info,
continue;
if (ref->count == 0)
continue;
+ if (root_objectid && ref->root_id != root_objectid) {
+ ret = BACKREF_FOUND_SHARED;
+ goto out;
+ }
err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
parents, extent_item_pos,
total_refs);
@@ -562,7 +570,8 @@ static void __merge_refs(struct list_head *head, int mode)
* smaller or equal that seq to the list
*/
static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
- struct list_head *prefs, u64 *total_refs)
+ struct list_head *prefs, u64 *total_refs,
+ u64 inum)
{
struct btrfs_delayed_extent_op *extent_op = head->extent_op;
struct rb_node *n = &head->node.rb_node;
@@ -626,6 +635,16 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head
*head, u64 seq,
key.objectid = ref->objectid;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = ref->offset;
+
+ /*
+ * Found a inum that doesn't match our known inum, we
+ * know it's shared.
+ */
+ if (inum && ref->objectid != inum) {
+ ret = BACKREF_FOUND_SHARED;
+ break;
+ }
+
ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
node->bytenr,
node->ref_mod * sgn, GFP_ATOMIC);
@@ -660,7 +679,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head
*head, u64 seq,
static int __add_inline_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
int *info_level, struct list_head *prefs,
- u64 *total_refs)
+ u64 *total_refs, u64 inum)
{
int ret = 0;
int slot;
@@ -745,6 +764,12 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
+
+ if (inum && key.objectid != inum) {
+ ret = BACKREF_FOUND_SHARED;
+ break;
+ }
+
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0,
bytenr, count, GFP_NOFS);
@@ -766,7 +791,7 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
*/
static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
struct btrfs_path *path, u64 bytenr,
- int info_level, struct list_head *prefs)
+ int info_level, struct list_head *prefs, u64 inum)
{
struct btrfs_root *extent_root = fs_info->extent_root;
int ret;
@@ -828,6 +853,12 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
dref);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_extent_data_ref_offset(leaf, dref);
+
+ if (inum && key.objectid != inum) {
+ ret = BACKREF_FOUND_SHARED;
+ break;
+ }
+
root = btrfs_extent_data_ref_root(leaf, dref);
ret = __add_prelim_ref(prefs, root, &key, 0, 0,
bytenr, count, GFP_NOFS);
@@ -855,7 +886,8 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
static int find_parent_nodes(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 bytenr,
u64 time_seq, struct ulist *refs,
- struct ulist *roots, const u64 *extent_item_pos)
+ struct ulist *roots, const u64 *extent_item_pos,
+ u64 root_objectid, u64 inum)
{
struct btrfs_key key;
struct btrfs_path *path;
@@ -930,7 +962,8 @@ again:
}
spin_unlock(&delayed_refs->lock);
ret = __add_delayed_refs(head, time_seq,
- &prefs_delayed, &total_refs);
+ &prefs_delayed, &total_refs,
+ inum);
mutex_unlock(&head->mutex);
if (ret)
goto out;
@@ -952,11 +985,11 @@ again:
key.type == BTRFS_METADATA_ITEM_KEY)) {
ret = __add_inline_refs(fs_info, path, bytenr,
&info_level, &prefs,
- &total_refs);
+ &total_refs, inum);
if (ret)
goto out;
ret = __add_keyed_refs(fs_info, path, bytenr,
- info_level, &prefs);
+ info_level, &prefs, inum);
if (ret)
goto out;
}
@@ -972,7 +1005,8 @@ again:
__merge_refs(&prefs, 1);
ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
- extent_item_pos, total_refs);
+ extent_item_pos, total_refs,
+ root_objectid);
if (ret)
goto out;
@@ -982,6 +1016,11 @@ again:
ref = list_first_entry(&prefs, struct __prelim_ref, list);
WARN_ON(ref->count < 0);
if (roots && ref->count && ref->root_id &&
ref->parent == 0) {
+ if (root_objectid && ref->root_id != root_objectid) {
+ ret = BACKREF_FOUND_SHARED;
+ goto out;
+ }
+
/* no parent == root of tree */
ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
if (ret < 0)
@@ -1085,7 +1124,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle
*trans,
return -ENOMEM;
ret = find_parent_nodes(trans, fs_info, bytenr,
- time_seq, *leafs, NULL, extent_item_pos);
+ time_seq, *leafs, NULL, extent_item_pos, 0, 0);
if (ret < 0 && ret != -ENOENT) {
free_leaf_list(*leafs);
return ret;
@@ -1128,7 +1167,7 @@ static int __btrfs_find_all_roots(struct
btrfs_trans_handle *trans,
ULIST_ITER_INIT(&uiter);
while (1) {
ret = find_parent_nodes(trans, fs_info, bytenr,
- time_seq, tmp, *roots, NULL);
+ time_seq, tmp, *roots, NULL, 0, 0);
if (ret < 0 && ret != -ENOENT) {
ulist_free(tmp);
ulist_free(*roots);
@@ -1159,6 +1198,54 @@ int btrfs_find_all_roots(struct btrfs_trans_handle
*trans,
return ret;
}
+int btrfs_check_shared(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_info *fs_info, u64 root_objectid,
+ u64 inum, u64 bytenr)
+{
+ struct ulist *tmp = NULL;
+ struct ulist *roots = NULL;
+ struct ulist_iterator uiter;
+ struct ulist_node *node;
+ struct seq_list elem = {};
+ int ret = 0;
+
+ tmp = ulist_alloc(GFP_NOFS);
+ roots = ulist_alloc(GFP_NOFS);
+ if (!tmp || !roots) {
+ ulist_free(tmp);
+ ulist_free(roots);
+ return -ENOMEM;
+ }
+
+ if (trans)
+ btrfs_get_tree_mod_seq(fs_info, &elem);
+ else
+ down_read(&fs_info->commit_root_sem);
+ ULIST_ITER_INIT(&uiter);
+ while (1) {
+ ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
+ roots, NULL, root_objectid, inum);
+ if (ret == BACKREF_FOUND_SHARED) {
+ ret = 1;
+ break;
+ }
+ if (ret < 0 && ret != -ENOENT)
+ break;
+ node = ulist_next(tmp, &uiter);
+ if (!node)
+ break;
+ bytenr = node->val;
+ cond_resched();
+ }
+ if (trans)
+ btrfs_put_tree_mod_seq(fs_info, &elem);
+ else
+ up_read(&fs_info->commit_root_sem);
+ ulist_free(tmp);
+ ulist_free(roots);
+ return ret;
+}
+
/*
* this makes the path point to (inum INODE_ITEM ioff)
*/
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index 94e9442..71fef59 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -71,6 +71,9 @@ int btrfs_find_one_extref(struct btrfs_root *root, u64
inode_objectid,
u64 start_off, struct btrfs_path *path,
struct btrfs_inode_extref **ret_extref,
u64 *found_off);
+int btrfs_check_shared(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_info *fs_info, u64 root_objectid,
+ u64 inum, u64 bytenr);
int __init btrfs_prelim_ref_init(void);
void btrfs_prelim_ref_exit(void);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8285ed0..d5fb685 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4113,19 +4113,6 @@ static struct extent_map *get_extent_skip_holes(struct
inode *inode,
return NULL;
}
-static noinline int count_ext_ref(u64 inum, u64 offset, u64 root_id, void *ctx)
-{
- unsigned long cnt = *((unsigned long *)ctx);
-
- cnt++;
- *((unsigned long *)ctx) = cnt;
-
- /* Now we're sure that the extent is shared. */
- if (cnt > 1)
- return 1;
- return 0;
-}
-
int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len, get_extent_t *get_extent)
{
@@ -4142,6 +4129,7 @@ int extent_fiemap(struct inode *inode, struct
fiemap_extent_info *fieinfo,
struct extent_map *em = NULL;
struct extent_state *cached_state = NULL;
struct btrfs_path *path;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
int end = 0;
u64 em_start = 0;
u64 em_len = 0;
@@ -4155,15 +4143,15 @@ int extent_fiemap(struct inode *inode, struct
fiemap_extent_info *fieinfo,
return -ENOMEM;
path->leave_spinning = 1;
- start = ALIGN(start, BTRFS_I(inode)->root->sectorsize);
- len = ALIGN(len, BTRFS_I(inode)->root->sectorsize);
+ start = ALIGN(start, root->sectorsize);
+ len = ALIGN(len, root->sectorsize);
/*
* lookup the last file extent. We're not using i_size here
* because there might be preallocation past i_size
*/
- ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root,
- path, btrfs_ino(inode), -1, 0);
+ ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode), -1,
+ 0);
if (ret < 0) {
btrfs_free_path(path);
return ret;
@@ -4256,25 +4244,27 @@ int extent_fiemap(struct inode *inode, struct
fiemap_extent_info *fieinfo,
} else if (em->block_start == EXTENT_MAP_DELALLOC) {
flags |= (FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
- } else {
- unsigned long ref_cnt = 0;
+ } else if (fieinfo->fi_extents_max) {
+ u64 bytenr = em->block_start -
+ (em->start - em->orig_start);
disko = em->block_start + offset_in_extent;
/*
* As btrfs supports shared space, this information
* can be exported to userspace tools via
- * flag FIEMAP_EXTENT_SHARED.
+ * flag FIEMAP_EXTENT_SHARED. If fi_extents_max == 0
+ * then we're just getting a count and we can skip the
+ * lookup stuff.
*/
- ret = iterate_inodes_from_logical(
- em->block_start,
- BTRFS_I(inode)->root->fs_info,
- path, count_ext_ref, &ref_cnt);
- if (ret < 0 && ret != -ENOENT)
+ ret = btrfs_check_shared(NULL, root->fs_info,
+ root->objectid,
+ btrfs_ino(inode), bytenr);
+ if (ret < 0)
goto out_free;
-
- if (ref_cnt > 1)
+ if (ret)
flags |= FIEMAP_EXTENT_SHARED;
+ ret = 0;
}
if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
flags |= FIEMAP_EXTENT_ENCODED;
--
1.8.3.1
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