Filipe David Borba Manana
2014-Feb-15 15:55 UTC
[PATCH] Btrfs: don't insert useless holes when punching beyond the inode's size
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>
---
fs/btrfs/file.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 006af2f..5133d71 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2165,6 +2165,7 @@ 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)
@@ -2180,14 +2181,14 @@ 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);
@@ -2196,7 +2197,7 @@ 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);
@@ -2285,10 +2286,13 @@ 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;
@@ -2321,10 +2325,12 @@ 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:
--
1.7.9.5
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