Skip to content

Commit

Permalink
Btrfs: Fix race in btrfs_mark_extent_written
Browse files Browse the repository at this point in the history 
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>
  • Loading branch information
Yan, Zheng authored and Chris Mason committed Jan 18, 2010
1 parent 2423fdf commit 6c7d54a
Showing 1 changed file with 80 additions and 20 deletions.
100 changes: 80 additions & 20 deletions fs/btrfs/file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -506,7 +506,8 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
}

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;
Expand All @@ -522,6 +523,7 @@ static int extent_mergeable(struct extent_buffer *leaf, int slot,
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))
Expand Down Expand Up @@ -561,13 +563,15 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
u64 split;
int del_nr = 0;
int del_slot = 0;
int recow;
int ret;

btrfs_drop_extent_cache(inode, start, end - 1, 0);

path = btrfs_alloc_path();
BUG_ON(!path);
again:
recow = 0;
split = start;
key.objectid = inode->i_ino;
key.type = BTRFS_EXTENT_DATA_KEY;
Expand All @@ -591,12 +595,60 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
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) {
Expand Down Expand Up @@ -631,15 +683,18 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
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++;
Expand All @@ -650,8 +705,13 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
}
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++;
Expand All @@ -660,22 +720,22 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
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;
Expand Down

0 comments on commit 6c7d54a

Please sign in to comment.