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d6589101b6
When cloning/deduplicating file extents (through the clone and extent_same
ioctls) we can get data back references with offset values that are a
result of an unsigned integer arithmetic underflow, that is, values that
are much larger then they could be otherwise.
This is not a problem when decrementing or dropping the back references
(happens when we overwrite the extents or punch a hole for example, through
__btrfs_drop_extents()), since we compute the same too large offset value,
but it is a problem for the backref walking code, used by an incremental
send and the ioctls that are used by the btrfs tool "inspect-internal"
commands, as it makes it miss the corresponding file extent items because
the search key is set for an extent item that starts at an offset matching
the exceptionally large offset value of the data back reference. For an
incremental send this causes the send ioctl to fail with -EIO.
So teach the backref walking code to deal with these cases by setting the
search key's offset to 0 if the backref's offset value is larger than
LLONG_MAX (the largest possible file offset). This makes sure the backref
walking code finds the corresponding file extent items at the expense of
scanning more items and leafs in the btree.
Fixing the clone/dedup ioctls to not produce such underflowed results would
require major changes breaking backward compatibility, updating user space
tools, etc.
Simple reproducer case for fstests:
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
rm -fr $send_files_dir
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
# real QA test starts here
_supported_fs btrfs
_supported_os Linux
_require_scratch
_require_cloner
_need_to_be_root
send_files_dir=$TEST_DIR/btrfs-test-$seq
rm -f $seqres.full
rm -fr $send_files_dir
mkdir $send_files_dir
_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount
# Create our test file with a single extent of 64K starting at file
# offset 128K.
$XFS_IO_PROG -f -c "pwrite -S 0xaa 128K 64K" $SCRATCH_MNT/foo \
| _filter_xfs_io
_run_btrfs_util_prog subvolume snapshot -r $SCRATCH_MNT \
$SCRATCH_MNT/mysnap1
# Now clone parts of the original extent into lower offsets of the file.
#
# The first clone operation adds a file extent item to file offset 0
# that points to our initial extent with a data offset of 16K. The
# corresponding data back reference in the extent tree has an offset of
# 18446744073709535232, which is the result of file_offset - data_offset
# = 0 - 16K.
#
# The second clone operation adds a file extent item to file offset 16K
# that points to our initial extent with a data offset of 48K. The
# corresponding data back reference in the extent tree has an offset of
# 18446744073709518848, which is the result of file_offset - data_offset
# = 16K - 48K.
#
# Those large back reference offsets (result of unsigned arithmetic
# underflow) confused the back reference walking code (used by an
# incremental send and the multiple inspect-internal ioctls) and made it
# miss the back references, which for the case of an incremental send it
# made it fail with -EIO and print a message like the following to
# dmesg:
#
# "BTRFS error (device sdc): did not find backref in send_root. \
# inode=257, offset=0, disk_byte=12845056 found extent=12845056"
#
$CLONER_PROG -s $(((128 + 16) * 1024)) -d 0 -l $((16 * 1024)) \
$SCRATCH_MNT/foo $SCRATCH_MNT/foo
$CLONER_PROG -s $(((128 + 48) * 1024)) -d $((16 * 1024)) \
-l $((16 * 1024)) $SCRATCH_MNT/foo $SCRATCH_MNT/foo
_run_btrfs_util_prog subvolume snapshot -r $SCRATCH_MNT \
$SCRATCH_MNT/mysnap2
_run_btrfs_util_prog send $SCRATCH_MNT/mysnap1 -f $send_files_dir/1.snap
_run_btrfs_util_prog send -p $SCRATCH_MNT/mysnap1 $SCRATCH_MNT/mysnap2 \
-f $send_files_dir/2.snap
echo "File digest in the original filesystem:"
md5sum $SCRATCH_MNT/mysnap2/foo | _filter_scratch
# Now recreate the filesystem by receiving both send streams and verify
# we get the same file contents that the original filesystem had.
_scratch_unmount
_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount
_run_btrfs_util_prog receive $SCRATCH_MNT -f $send_files_dir/1.snap
_run_btrfs_util_prog receive $SCRATCH_MNT -f $send_files_dir/2.snap
echo "File digest in the new filesystem:"
md5sum $SCRATCH_MNT/mysnap2/foo | _filter_scratch
status=0
exit
The test's expected golden output is:
wrote 65536/65536 bytes at offset 131072
XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
File digest in the original filesystem:
6c6079335cff141b8a31233ead04cbff SCRATCH_MNT/mysnap2/foo
File digest in the new filesystem:
6c6079335cff141b8a31233ead04cbff SCRATCH_MNT/mysnap2/foo
But it failed with:
(...)
@@ -1,7 +1,5 @@
QA output created by 097
wrote 65536/65536 bytes at offset 131072
XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-File digest in the original filesystem:
-6c6079335cff141b8a31233ead04cbff SCRATCH_MNT/mysnap2/foo
-File digest in the new filesystem:
-6c6079335cff141b8a31233ead04cbff SCRATCH_MNT/mysnap2/foo
...
$ cat /home/fdmanana/git/hub/xfstests/results//btrfs/097.full
(...)
ERROR: send ioctl failed with -5: Input/output error
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
|
||
|---|---|---|
| .. | ||
| tests | ||
| acl.c | ||
| async-thread.c | ||
| async-thread.h | ||
| backref.c | ||
| backref.h | ||
| btrfs_inode.h | ||
| check-integrity.c | ||
| check-integrity.h | ||
| compression.c | ||
| compression.h | ||
| ctree.c | ||
| ctree.h | ||
| delayed-inode.c | ||
| delayed-inode.h | ||
| delayed-ref.c | ||
| delayed-ref.h | ||
| dev-replace.c | ||
| dev-replace.h | ||
| dir-item.c | ||
| disk-io.c | ||
| disk-io.h | ||
| export.c | ||
| export.h | ||
| extent_io.c | ||
| extent_io.h | ||
| extent_map.c | ||
| extent_map.h | ||
| extent-tree.c | ||
| extent-tree.h | ||
| file-item.c | ||
| file.c | ||
| free-space-cache.c | ||
| free-space-cache.h | ||
| hash.c | ||
| hash.h | ||
| inode-item.c | ||
| inode-map.c | ||
| inode-map.h | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| locking.c | ||
| locking.h | ||
| lzo.c | ||
| Makefile | ||
| math.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 | ||
| relocation.c | ||
| root-tree.c | ||
| scrub.c | ||
| send.c | ||
| send.h | ||
| struct-funcs.c | ||
| super.c | ||
| sysfs.c | ||
| sysfs.h | ||
| transaction.c | ||
| transaction.h | ||
| tree-defrag.c | ||
| tree-log.c | ||
| tree-log.h | ||
| ulist.c | ||
| ulist.h | ||
| uuid-tree.c | ||
| volumes.c | ||
| volumes.h | ||
| xattr.c | ||
| xattr.h | ||
| zlib.c | ||