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Subject[064/111] Btrfs: Fix race in btrfs_mark_extent_written
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Yan, Zheng <zheng.yan@oracle.com>

commit 6c7d54ac87f338c479d9729e8392eca3f76e11e1 upstream.

Fix bug reported by Johannes Hirte. The reason of that bug
is btrfs_del_items is called after btrfs_duplicate_item and
btrfs_del_items triggers tree balance. The fix is check that
case and call btrfs_search_slot when needed.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/btrfs/file.c | 100 ++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 80 insertions(+), 20 deletions(-)

--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -506,7 +506,8 @@ next_slot:
}

static int extent_mergeable(struct extent_buffer *leaf, int slot,
- u64 objectid, u64 bytenr, u64 *start, u64 *end)
+ u64 objectid, u64 bytenr, u64 orig_offset,
+ u64 *start, u64 *end)
{
struct btrfs_file_extent_item *fi;
struct btrfs_key key;
@@ -522,6 +523,7 @@ static int extent_mergeable(struct exten
fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||
+ btrfs_file_extent_offset(leaf, fi) != key.offset - orig_offset ||
btrfs_file_extent_compression(leaf, fi) ||
btrfs_file_extent_encryption(leaf, fi) ||
btrfs_file_extent_other_encoding(leaf, fi))
@@ -561,6 +563,7 @@ int btrfs_mark_extent_written(struct btr
u64 split;
int del_nr = 0;
int del_slot = 0;
+ int recow;
int ret;

btrfs_drop_extent_cache(inode, start, end - 1, 0);
@@ -568,6 +571,7 @@ int btrfs_mark_extent_written(struct btr
path = btrfs_alloc_path();
BUG_ON(!path);
again:
+ recow = 0;
split = start;
key.objectid = inode->i_ino;
key.type = BTRFS_EXTENT_DATA_KEY;
@@ -591,12 +595,60 @@ again:
bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
orig_offset = key.offset - btrfs_file_extent_offset(leaf, fi);
+ memcpy(&new_key, &key, sizeof(new_key));
+
+ if (start == key.offset && end < extent_end) {
+ other_start = 0;
+ other_end = start;
+ if (extent_mergeable(leaf, path->slots[0] - 1,
+ inode->i_ino, bytenr, orig_offset,
+ &other_start, &other_end)) {
+ new_key.offset = end;
+ btrfs_set_item_key_safe(trans, root, path, &new_key);
+ fi = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
+ btrfs_set_file_extent_num_bytes(leaf, fi,
+ extent_end - end);
+ btrfs_set_file_extent_offset(leaf, fi,
+ end - orig_offset);
+ fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
+ struct btrfs_file_extent_item);
+ btrfs_set_file_extent_num_bytes(leaf, fi,
+ end - other_start);
+ btrfs_mark_buffer_dirty(leaf);
+ goto out;
+ }
+ }
+
+ if (start > key.offset && end == extent_end) {
+ other_start = end;
+ other_end = 0;
+ if (extent_mergeable(leaf, path->slots[0] + 1,
+ inode->i_ino, bytenr, orig_offset,
+ &other_start, &other_end)) {
+ fi = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
+ btrfs_set_file_extent_num_bytes(leaf, fi,
+ start - key.offset);
+ path->slots[0]++;
+ new_key.offset = start;
+ btrfs_set_item_key_safe(trans, root, path, &new_key);
+
+ fi = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
+ btrfs_set_file_extent_num_bytes(leaf, fi,
+ other_end - start);
+ btrfs_set_file_extent_offset(leaf, fi,
+ start - orig_offset);
+ btrfs_mark_buffer_dirty(leaf);
+ goto out;
+ }
+ }

while (start > key.offset || end < extent_end) {
if (key.offset == start)
split = end;

- memcpy(&new_key, &key, sizeof(new_key));
new_key.offset = split;
ret = btrfs_duplicate_item(trans, root, path, &new_key);
if (ret == -EAGAIN) {
@@ -631,15 +683,18 @@ again:
path->slots[0]--;
extent_end = end;
}
+ recow = 1;
}

- fi = btrfs_item_ptr(leaf, path->slots[0],
- struct btrfs_file_extent_item);
-
other_start = end;
other_end = 0;
- if (extent_mergeable(leaf, path->slots[0] + 1, inode->i_ino,
- bytenr, &other_start, &other_end)) {
+ if (extent_mergeable(leaf, path->slots[0] + 1,
+ inode->i_ino, bytenr, orig_offset,
+ &other_start, &other_end)) {
+ if (recow) {
+ btrfs_release_path(root, path);
+ goto again;
+ }
extent_end = other_end;
del_slot = path->slots[0] + 1;
del_nr++;
@@ -650,8 +705,13 @@ again:
}
other_start = 0;
other_end = start;
- if (extent_mergeable(leaf, path->slots[0] - 1, inode->i_ino,
- bytenr, &other_start, &other_end)) {
+ if (extent_mergeable(leaf, path->slots[0] - 1,
+ inode->i_ino, bytenr, orig_offset,
+ &other_start, &other_end)) {
+ if (recow) {
+ btrfs_release_path(root, path);
+ goto again;
+ }
key.offset = other_start;
del_slot = path->slots[0];
del_nr++;
@@ -660,22 +720,22 @@ again:
inode->i_ino, orig_offset);
BUG_ON(ret);
}
+ fi = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
if (del_nr == 0) {
btrfs_set_file_extent_type(leaf, fi,
BTRFS_FILE_EXTENT_REG);
btrfs_mark_buffer_dirty(leaf);
- goto out;
- }
-
- fi = btrfs_item_ptr(leaf, del_slot - 1,
- struct btrfs_file_extent_item);
- btrfs_set_file_extent_type(leaf, fi, BTRFS_FILE_EXTENT_REG);
- btrfs_set_file_extent_num_bytes(leaf, fi,
- extent_end - key.offset);
- btrfs_mark_buffer_dirty(leaf);
+ } else {
+ btrfs_set_file_extent_type(leaf, fi,
+ BTRFS_FILE_EXTENT_REG);
+ btrfs_set_file_extent_num_bytes(leaf, fi,
+ extent_end - key.offset);
+ btrfs_mark_buffer_dirty(leaf);

- ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
- BUG_ON(ret);
+ ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+ BUG_ON(ret);
+ }
out:
btrfs_free_path(path);
return 0;



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