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During an incremental send operation, when processing the new references
for the current inode, we might send an unlink operation for another inode
that has a conflicting path and has more than one hard link. However this
path was computed and cached before we processed previous new references
for the current inode. We may have orphanized a directory of that path
while processing a previous new reference, in which case the path will
be invalid and cause the receiver process to fail.
The following reproducer triggers the problem and explains how/why it
happens in its comments:
$ cat test-send-unlink.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV >/dev/null
mount $DEV $MNT
# Create our test files and directory. Inode 259 (file3) has two hard
# links.
touch $MNT/file1
touch $MNT/file2
touch $MNT/file3
mkdir $MNT/A
ln $MNT/file3 $MNT/A/hard_link
# Filesystem looks like:
#
# . (ino 256)
# |----- file1 (ino 257)
# |----- file2 (ino 258)
# |----- file3 (ino 259)
# |----- A/ (ino 260)
# |---- hard_link (ino 259)
#
# Now create the base snapshot, which is going to be the parent snapshot
# for a later incremental send.
btrfs subvolume snapshot -r $MNT $MNT/snap1
btrfs send -f /tmp/snap1.send $MNT/snap1
# Move inode 257 into directory inode 260. This results in computing the
# path for inode 260 as "/A" and caching it.
mv $MNT/file1 $MNT/A/file1
# Move inode 258 (file2) into directory inode 260, with a name of
# "hard_link", moving first inode 259 away since it currently has that
# location and name.
mv $MNT/A/hard_link $MNT/tmp
mv $MNT/file2 $MNT/A/hard_link
# Now rename inode 260 to something else (B for example) and then create
# a hard link for inode 258 that has the old name and location of inode
# 260 ("/A").
mv $MNT/A $MNT/B
ln $MNT/B/hard_link $MNT/A
# Filesystem now looks like:
#
# . (ino 256)
# |----- tmp (ino 259)
# |----- file3 (ino 259)
# |----- B/ (ino 260)
# | |---- file1 (ino 257)
# | |---- hard_link (ino 258)
# |
# |----- A (ino 258)
# Create another snapshot of our subvolume and use it for an incremental
# send.
btrfs subvolume snapshot -r $MNT $MNT/snap2
btrfs send -f /tmp/snap2.send -p $MNT/snap1 $MNT/snap2
# Now unmount the filesystem, create a new one, mount it and try to
# apply both send streams to recreate both snapshots.
umount $DEV
mkfs.btrfs -f $DEV >/dev/null
mount $DEV $MNT
# First add the first snapshot to the new filesystem by applying the
# first send stream.
btrfs receive -f /tmp/snap1.send $MNT
# The incremental receive operation below used to fail with the
# following error:
#
# ERROR: unlink A/hard_link failed: No such file or directory
#
# This is because when send is processing inode 257, it generates the
# path for inode 260 as "/A", since that inode is its parent in the send
# snapshot, and caches that path.
#
# Later when processing inode 258, it first processes its new reference
# that has the path of "/A", which results in orphanizing inode 260
# because there is a a path collision. This results in issuing a rename
# operation from "/A" to "/o260-6-0".
#
# Finally when processing the new reference "B/hard_link" for inode 258,
# it notices that it collides with inode 259 (not yet processed, because
# it has a higher inode number), since that inode has the name
# "hard_link" under the directory inode 260. It also checks that inode
# 259 has two hardlinks, so it decides to issue a unlink operation for
# the name "hard_link" for inode 259. However the path passed to the
# unlink operation is "/A/hard_link", which is incorrect since currently
# "/A" does not exists, due to the orphanization of inode 260 mentioned
# before. The path is incorrect because it was computed and cached
# before the orphanization. This results in the receiver to fail with
# the above error.
btrfs receive -f /tmp/snap2.send $MNT
umount $MNT
When running the test, it fails like this:
$ ./test-send-unlink.sh
Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1'
At subvol /mnt/sdi/snap1
Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2'
At subvol /mnt/sdi/snap2
At subvol snap1
At snapshot snap2
ERROR: unlink A/hard_link failed: No such file or directory
Fix this by recomputing a path before issuing an unlink operation when
processing the new references for the current inode if we previously
have orphanized a directory.
A test case for fstests will follow soon.
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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|---|---|---|
| .. | ||
| tests | ||
| acl.c | ||
| async-thread.c | ||
| async-thread.h | ||
| backref.c | ||
| backref.h | ||
| block-group.c | ||
| block-group.h | ||
| block-rsv.c | ||
| block-rsv.h | ||
| btrfs_inode.h | ||
| check-integrity.c | ||
| check-integrity.h | ||
| compression.c | ||
| compression.h | ||
| ctree.c | ||
| ctree.h | ||
| delalloc-space.c | ||
| delalloc-space.h | ||
| delayed-inode.c | ||
| delayed-inode.h | ||
| delayed-ref.c | ||
| delayed-ref.h | ||
| dev-replace.c | ||
| dev-replace.h | ||
| dir-item.c | ||
| discard.c | ||
| discard.h | ||
| disk-io.c | ||
| disk-io.h | ||
| export.c | ||
| export.h | ||
| extent_io.c | ||
| extent_io.h | ||
| extent_map.c | ||
| extent_map.h | ||
| extent-io-tree.h | ||
| extent-tree.c | ||
| file-item.c | ||
| file.c | ||
| free-space-cache.c | ||
| free-space-cache.h | ||
| free-space-tree.c | ||
| free-space-tree.h | ||
| inode-item.c | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| locking.c | ||
| locking.h | ||
| lzo.c | ||
| Makefile | ||
| misc.h | ||
| ordered-data.c | ||
| ordered-data.h | ||
| orphan.c | ||
| print-tree.c | ||
| print-tree.h | ||
| props.c | ||
| props.h | ||
| qgroup.c | ||
| qgroup.h | ||
| raid56.c | ||
| raid56.h | ||
| rcu-string.h | ||
| reada.c | ||
| ref-verify.c | ||
| ref-verify.h | ||
| reflink.c | ||
| reflink.h | ||
| relocation.c | ||
| root-tree.c | ||
| scrub.c | ||
| send.c | ||
| send.h | ||
| space-info.c | ||
| space-info.h | ||
| struct-funcs.c | ||
| subpage.c | ||
| subpage.h | ||
| super.c | ||
| sysfs.c | ||
| sysfs.h | ||
| transaction.c | ||
| transaction.h | ||
| tree-checker.c | ||
| tree-checker.h | ||
| tree-defrag.c | ||
| tree-log.c | ||
| tree-log.h | ||
| tree-mod-log.c | ||
| tree-mod-log.h | ||
| ulist.c | ||
| ulist.h | ||
| uuid-tree.c | ||
| volumes.c | ||
| volumes.h | ||
| xattr.c | ||
| xattr.h | ||
| zlib.c | ||
| zoned.c | ||
| zoned.h | ||
| zstd.c | ||