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author | Filipe Manana <fdmanana@suse.com> | 2015-06-25 04:17:46 +0100 |
---|---|---|
committer | Chris Mason <clm@fb.com> | 2015-07-01 17:17:12 -0700 |
commit | a89ca6f24ffe435edad57de02eaabd37a2c6bff6 (patch) | |
tree | 9428cf5260c00f66637d29f3d8c37902c6127ddb /fs/btrfs | |
parent | 36283bf777d963fac099213297e155d071096994 (diff) | |
download | linux-a89ca6f24ffe435edad57de02eaabd37a2c6bff6.tar.bz2 |
Btrfs: fix fsync after truncate when no_holes feature is enabled
When we have the no_holes feature enabled, if a we truncate a file to a
smaller size, truncate it again but to a size greater than or equals to
its original size and fsync it, the log tree will not have any information
about the hole covering the range [truncate_1_offset, new_file_size[.
Which means if the fsync log is replayed, the file will remain with the
state it had before both truncate operations.
Without the no_holes feature this does not happen, since when the inode
is logged (full sync flag is set) it will find in the fs/subvol tree a
leaf with a generation matching the current transaction id that has an
explicit extent item representing the hole.
Fix this by adding an explicit extent item representing a hole between
the last extent and the inode's i_size if we are doing a full sync.
The issue is easy to reproduce with the following test case for fstests:
. ./common/rc
. ./common/filter
. ./common/dmflakey
_need_to_be_root
_supported_fs generic
_supported_os Linux
_require_scratch
_require_dm_flakey
# This test was motivated by an issue found in btrfs when the btrfs
# no-holes feature is enabled (introduced in kernel 3.14). So enable
# the feature if the fs being tested is btrfs.
if [ $FSTYP == "btrfs" ]; then
_require_btrfs_fs_feature "no_holes"
_require_btrfs_mkfs_feature "no-holes"
MKFS_OPTIONS="$MKFS_OPTIONS -O no-holes"
fi
rm -f $seqres.full
_scratch_mkfs >>$seqres.full 2>&1
_init_flakey
_mount_flakey
# Create our test files and make sure everything is durably persisted.
$XFS_IO_PROG -f -c "pwrite -S 0xaa 0 64K" \
-c "pwrite -S 0xbb 64K 61K" \
$SCRATCH_MNT/foo | _filter_xfs_io
$XFS_IO_PROG -f -c "pwrite -S 0xee 0 64K" \
-c "pwrite -S 0xff 64K 61K" \
$SCRATCH_MNT/bar | _filter_xfs_io
sync
# Now truncate our file foo to a smaller size (64Kb) and then truncate
# it to the size it had before the shrinking truncate (125Kb). Then
# fsync our file. If a power failure happens after the fsync, we expect
# our file to have a size of 125Kb, with the first 64Kb of data having
# the value 0xaa and the second 61Kb of data having the value 0x00.
$XFS_IO_PROG -c "truncate 64K" \
-c "truncate 125K" \
-c "fsync" \
$SCRATCH_MNT/foo
# Do something similar to our file bar, but the first truncation sets
# the file size to 0 and the second truncation expands the size to the
# double of what it was initially.
$XFS_IO_PROG -c "truncate 0" \
-c "truncate 253K" \
-c "fsync" \
$SCRATCH_MNT/bar
_load_flakey_table $FLAKEY_DROP_WRITES
_unmount_flakey
# Allow writes again, mount to trigger log replay and validate file
# contents.
_load_flakey_table $FLAKEY_ALLOW_WRITES
_mount_flakey
# We expect foo to have a size of 125Kb, the first 64Kb of data all
# having the value 0xaa and the remaining 61Kb to be a hole (all bytes
# with value 0x00).
echo "File foo content after log replay:"
od -t x1 $SCRATCH_MNT/foo
# We expect bar to have a size of 253Kb and no extents (any byte read
# from bar has the value 0x00).
echo "File bar content after log replay:"
od -t x1 $SCRATCH_MNT/bar
status=0
exit
The expected file contents in the golden output are:
File foo content after log replay:
0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa
*
0200000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0372000
File bar content after log replay:
0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0772000
Without this fix, their contents are:
File foo content after log replay:
0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa
*
0200000 bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
*
0372000
File bar content after log replay:
0000000 ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee
*
0200000 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
*
0372000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0772000
A test case submission for fstests follows soon.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs/btrfs')
-rw-r--r-- | fs/btrfs/tree-log.c | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 66f87156882f..9c45431e69ab 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -4197,6 +4197,107 @@ static int btrfs_log_all_xattrs(struct btrfs_trans_handle *trans, return 0; } +/* + * If the no holes feature is enabled we need to make sure any hole between the + * last extent and the i_size of our inode is explicitly marked in the log. This + * is to make sure that doing something like: + * + * 1) create file with 128Kb of data + * 2) truncate file to 64Kb + * 3) truncate file to 256Kb + * 4) fsync file + * 5) <crash/power failure> + * 6) mount fs and trigger log replay + * + * Will give us a file with a size of 256Kb, the first 64Kb of data match what + * the file had in its first 64Kb of data at step 1 and the last 192Kb of the + * file correspond to a hole. The presence of explicit holes in a log tree is + * what guarantees that log replay will remove/adjust file extent items in the + * fs/subvol tree. + * + * Here we do not need to care about holes between extents, that is already done + * by copy_items(). We also only need to do this in the full sync path, where we + * lookup for extents from the fs/subvol tree only. In the fast path case, we + * lookup the list of modified extent maps and if any represents a hole, we + * insert a corresponding extent representing a hole in the log tree. + */ +static int btrfs_log_trailing_hole(struct btrfs_trans_handle *trans, + struct btrfs_root *root, + struct inode *inode, + struct btrfs_path *path) +{ + int ret; + struct btrfs_key key; + u64 hole_start; + u64 hole_size; + struct extent_buffer *leaf; + struct btrfs_root *log = root->log_root; + const u64 ino = btrfs_ino(inode); + const u64 i_size = i_size_read(inode); + + if (!btrfs_fs_incompat(root->fs_info, NO_HOLES)) + return 0; + + key.objectid = ino; + key.type = BTRFS_EXTENT_DATA_KEY; + key.offset = (u64)-1; + + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + ASSERT(ret != 0); + if (ret < 0) + return ret; + + ASSERT(path->slots[0] > 0); + path->slots[0]--; + leaf = path->nodes[0]; + btrfs_item_key_to_cpu(leaf, &key, path->slots[0]); + + if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) { + /* inode does not have any extents */ + hole_start = 0; + hole_size = i_size; + } else { + struct btrfs_file_extent_item *extent; + u64 len; + + /* + * If there's an extent beyond i_size, an explicit hole was + * already inserted by copy_items(). + */ + if (key.offset >= i_size) + return 0; + + extent = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_file_extent_item); + + if (btrfs_file_extent_type(leaf, extent) == + BTRFS_FILE_EXTENT_INLINE) { + len = btrfs_file_extent_inline_len(leaf, + path->slots[0], + extent); + ASSERT(len == i_size); + return 0; + } + + len = btrfs_file_extent_num_bytes(leaf, extent); + /* Last extent goes beyond i_size, no need to log a hole. */ + if (key.offset + len > i_size) + return 0; + hole_start = key.offset + len; + hole_size = i_size - hole_start; + } + btrfs_release_path(path); + + /* Last extent ends at i_size. */ + if (hole_size == 0) + return 0; + + hole_size = ALIGN(hole_size, root->sectorsize); + ret = btrfs_insert_file_extent(trans, log, ino, hole_start, 0, 0, + hole_size, 0, hole_size, 0, 0, 0); + return ret; +} + /* log a single inode in the tree log. * At least one parent directory for this inode must exist in the tree * or be logged already. @@ -4460,6 +4561,13 @@ next_slot: err = btrfs_log_all_xattrs(trans, root, inode, path, dst_path); if (err) goto out_unlock; + if (max_key.type >= BTRFS_EXTENT_DATA_KEY && !fast_search) { + btrfs_release_path(path); + btrfs_release_path(dst_path); + err = btrfs_log_trailing_hole(trans, root, inode, path); + if (err) + goto out_unlock; + } log_extents: btrfs_release_path(path); btrfs_release_path(dst_path); |