new file mode 100755
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+#! /bin/bash
+# FSQA Test No. 095
+#
+# Regression test for adding and dropping an equal number of references for
+# file extents. Verify that if we drop N references for a file extent and we
+# add too N new references for that same file extent in the same transaction,
+# running the delayed references (always happens at transaction commit time)
+# does not fail.
+#
+# The regression was introduced in the 4.2-rc1 Linux kernel.
+#
+#-----------------------------------------------------------------------
+#
+# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
+# Author: Filipe Manana <fdmanana@suse.com>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+#-----------------------------------------------------------------------
+#
+
+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()
+{
+ _cleanup_flakey
+ rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmflakey
+
+# real QA test starts here
+_need_to_be_root
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+_require_dm_flakey
+_require_cloner
+_require_metadata_journaling $SCRATCH_DEV
+_require_xfs_io_command "falloc"
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+_init_flakey
+_mount_flakey
+
+# Create prealloc extent covering range [160K, 620K[
+$XFS_IO_PROG -f -c "falloc 160K 460K" $SCRATCH_MNT/foo
+
+# Now write to the last 80K of the prealloc extent plus 40K to the unallocated
+# space that immediately follows it. This creates a new extent of 40K that spans
+# the range [620K, 660K[.
+$XFS_IO_PROG -c "pwrite -S 0xaa 540K 120K" $SCRATCH_MNT/foo | _filter_xfs_io
+
+# At this point, there are now 2 back references to the prealloc extent in our
+# extent tree. Both are for our file offset 160K and one relates to a file
+# extent item with a data offset of 0 and a length of 380K, while the other
+# relates to a file extent item with a data offset of 380K and a length of 80K.
+
+# Make sure everything done so far is durably persisted (all back references are
+# in the extent tree, etc).
+sync
+
+# Now clone all extents of our file that cover the offset 160K up to its eof
+# (660K at this point) into itself at offset 2M. This leaves a hole in the file
+# covering the range [660K, 2M[. The prealloc extent will now be referenced by
+# the file twice, once for offset 160K and once for offset 2M. The 40K extent
+# that follows the prealloc extent will also be referenced twice by our file,
+# once for offset 620K and once for offset 2M + 460K.
+$CLONER_PROG -s $((160 * 1024)) -d $((2 * 1024 * 1024)) -l 0 $SCRATCH_MNT/foo \
+ $SCRATCH_MNT/foo
+
+# Now create one new extent in our file with a size of 100Kb. It will span the
+# range [3M, 3M + 100K[. It also will cause creation of a hole spanning the
+# range [2M + 460K, 3M[. Our new file size is 3M + 100K.
+$XFS_IO_PROG -c "pwrite -S 0xbb 3M 100K" $SCRATCH_MNT/foo | _filter_xfs_io
+
+# At this point, there are now (in memory) 4 back references to the prealloc
+# extent.
+#
+# Two of them are for file offset 160K, related to file extent items
+# matching the file offsets 160K and 540K respectively, with data offsets of
+# 0 and 380K respectively, and with lengths of 380K and 80K respectively.
+#
+# The other two references are for file offset 2M, related to file extent items
+# matching the file offsets 2M and 2M + 380K respectively, with data offsets of
+# 0 and 380K respectively, and with lengths of 380K and 80K respectively.
+#
+# The 40K extent has 2 back references, one for file offset 620K and the other
+# for file offset 2M + 460K.
+#
+# The 100K extent has a single back reference and it relates to file offset 3M.
+
+# Now clone our 100K extent into offset 600K. That offset covers the last 20K
+# of the prealloc extent, the whole 40K extent and 40K of the hole starting at
+# offset 660K.
+$CLONER_PROG -s $((3 * 1024 * 1024)) -d $((600 * 1024)) -l $((100 * 1024)) \
+ $SCRATCH_MNT/foo $SCRATCH_MNT/foo
+
+# At this point there's only one reference to the 40K extent, at file offset
+# 2M + 460K, we have 4 references for the prealloc extent (2 for file offset
+# 160K and 2 for file offset 2M) and 2 references for the 100K extent (1 for
+# file offset 3M and a new one for file offset 600K).
+
+# Now fsync our file to make all its new data and metadata updates are durably
+# persisted and present if a power failure/crash happens after a successful
+# fsync and before the next transaction commit.
+$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foo
+
+echo "File digest before power failure:"
+md5sum $SCRATCH_MNT/foo | _filter_scratch
+
+# Silently drop all writes and ummount to simulate a crash/power failure.
+_load_flakey_table $FLAKEY_DROP_WRITES
+_unmount_flakey
+
+# Allow writes again, mount to trigger log replay and validate file contents.
+# During log replay, the btrfs delayed references implementation used to run the
+# deletion of back references before the addition of new back references, which
+# made the addition fail as it didn't find the key in the extent tree that it
+# was looking for. The failure triggered by this test was related to the 40K
+# extent, which got 1 reference dropped and 1 reference added during the fsync
+# log replay - when running the delayed references at transaction commit time,
+# btrfs was applying the deletion before the insertion, resulting in a failure
+# of the insertion that ended up turning the fs into read-only mode.
+_load_flakey_table $FLAKEY_ALLOW_WRITES
+_mount_flakey
+
+echo "File digest after log replay:"
+md5sum $SCRATCH_MNT/foo | _filter_scratch
+
+_unmount_flakey
+
+status=0
+exit
new file mode 100644
@@ -0,0 +1,9 @@
+QA output created by 095
+wrote 122880/122880 bytes at offset 552960
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 102400/102400 bytes at offset 3145728
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+File digest before power failure:
+beaf47c36659ac29bb9363fb8ffa10a1 SCRATCH_MNT/foo
+File digest after log replay:
+beaf47c36659ac29bb9363fb8ffa10a1 SCRATCH_MNT/foo
@@ -96,3 +96,4 @@
092 auto quick send
093 auto quick clone
094 auto quick send
+095 auto quick metadata