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Btrfs: don't insert useless holes when punching beyond the inode's size

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If we punch beyond the size of an inode, we'll correctly remove any prealloc extents,
but we'll also insert file extent items representing holes (disk bytenr == 0) that start
with a key offset that lies beyond the inode's size and are not contiguous with the last
file extent item.

Example:

  $XFS_IO_PROG -f -c "truncate 118811" $SCRATCH_MNT/foo
  $XFS_IO_PROG -c "fpunch 582007 864596" $SCRATCH_MNT/foo
  $XFS_IO_PROG -c "pwrite -S 0x0d -b 39987 92267 39987" $SCRATCH_MNT/foo

btrfs-debug-tree output:

  item 4 key (257 INODE_ITEM 0) itemoff 15885 itemsize 160
	inode generation 6 transid 6 size 132254 block group 0 mode 100600 links 1
  item 5 key (257 INODE_REF 256) itemoff 15872 itemsize 13
	inode ref index 2 namelen 3 name: foo
  item 6 key (257 EXTENT_DATA 0) itemoff 15819 itemsize 53
	extent data disk byte 0 nr 0 gen 6
	extent data offset 0 nr 90112 ram 122880
	extent compression 0
  item 7 key (257 EXTENT_DATA 90112) itemoff 15766 itemsize 53
	extent data disk byte 12845056 nr 4096 gen 6
	extent data offset 0 nr 45056 ram 45056
	extent compression 2
  item 8 key (257 EXTENT_DATA 585728) itemoff 15713 itemsize 53
	extent data disk byte 0 nr 0 gen 6
	extent data offset 0 nr 860160 ram 860160
	extent compression 0

The last extent item, which represents a hole, is useless as it lies beyond the inode's
size.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
Filipe Manana 2014-02-15 15:55:58 +00:00 committed by Josef Bacik
parent 85fdfdf611
commit 12870f1c9b
1 changed files with 17 additions and 11 deletions
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28
fs/btrfs/file.c
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@ -2168,6 +2168,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
bool same_page = ((offset >> PAGE_CACHE_SHIFT) ==
((offset + len - 1) >> PAGE_CACHE_SHIFT));
bool no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
u64 ino_size = round_up(inode->i_size, PAGE_CACHE_SIZE);
ret = btrfs_wait_ordered_range(inode, offset, len);
if (ret)
@ -2183,14 +2184,14 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
* entire page.
*/
if (same_page && len < PAGE_CACHE_SIZE) {
if (offset < round_up(inode->i_size, PAGE_CACHE_SIZE))
if (offset < ino_size)
ret = btrfs_truncate_page(inode, offset, len, 0);
mutex_unlock(&inode->i_mutex);
return ret;
}
/* zero back part of the first page */
if (offset < round_up(inode->i_size, PAGE_CACHE_SIZE)) {
if (offset < ino_size) {
ret = btrfs_truncate_page(inode, offset, 0, 0);
if (ret) {
mutex_unlock(&inode->i_mutex);
@ -2199,7 +2200,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
}
/* zero the front end of the last page */
if (offset + len < round_up(inode->i_size, PAGE_CACHE_SIZE)) {
if (offset + len < ino_size) {
ret = btrfs_truncate_page(inode, offset + len, 0, 1);
if (ret) {
mutex_unlock(&inode->i_mutex);
@ -2288,10 +2289,13 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
trans->block_rsv = &root->fs_info->trans_block_rsv;
ret = fill_holes(trans, inode, path, cur_offset, drop_end);
if (ret) {
err = ret;
break;
if (cur_offset < ino_size) {
ret = fill_holes(trans, inode, path, cur_offset,
drop_end);
if (ret) {
err = ret;
break;
}
}
cur_offset = drop_end;
@ -2324,10 +2328,12 @@ static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
}
trans->block_rsv = &root->fs_info->trans_block_rsv;
ret = fill_holes(trans, inode, path, cur_offset, drop_end);
if (ret) {
err = ret;
goto out_trans;
if (cur_offset < ino_size) {
ret = fill_holes(trans, inode, path, cur_offset, drop_end);
if (ret) {
err = ret;
goto out_trans;
}
}
out_trans: