This is a long existing bug (from 2012) but exposed by a reporter
recently, that when compressed extent without data csum get written to
device-replace target device, the written data is in fact uncompressed data
other than the original compressed data.
And since btrfs still consider the data is compressed and will try to read it
as compressed, it can cause read error.
The root cause is located, and one RFC patch already sent to fix it,
titled "[PATCH] btrfs: scrub: Don't use inode pages for device replace".
(The RFC is only for the extra possible way to fix the bug, the fix
itself should work without problem)
Reported-by: James Harvey <jamespharve...@gmail.com>
Signed-off-by: Qu Wenruo <w...@suse.com>
---
changelog:
v2:
Now the fix patch is no longer RFC.
Remove _require_test as we don't really touch it.
Add comment on the mount cycle.
Add the test to group 'volume'.
---
tests/btrfs/161 | 91 +++++++++++++++++++++++++++++++++++++++++++++
tests/btrfs/161.out | 2 +
tests/btrfs/group | 1 +
3 files changed, 94 insertions(+)
create mode 100755 tests/btrfs/161
create mode 100644 tests/btrfs/161.out
diff --git a/tests/btrfs/161 b/tests/btrfs/161
new file mode 100755
index 00000000..ce1b0e04
--- /dev/null
+++ b/tests/btrfs/161
@@ -0,0 +1,91 @@
+#! /bin/bash
+# FS QA Test 161
+#
+# Test if btrfs will corrupt compressed data extent without data csum
+# by replacing it with uncompressed data, when doing replacing device.
+#
+# This could be fixed by the following RFC patch:
+# "[PATCH] btrfs: scrub: Don't use inode pages for device replace"
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2018 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# 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"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1 # failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+ cd /
+ rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch_dev_pool 2
+_require_scratch_dev_pool_equal_size
+
+
+_scratch_dev_pool_get 1
+_spare_dev_get
+_scratch_pool_mkfs >> $seqres.full 2>&1
+
+# Create nodatasum inode
+_scratch_mount "-o nodatasum"
+touch $SCRATCH_MNT/nodatasum_file
+_scratch_remount "datasum,compress"
+_pwrite_byte 0xcd 0 128K $SCRATCH_MNT/nodatasum_file > /dev/null
+
+# Write the compressed data back to disk
+sync
+
+# Replace the device
+_run_btrfs_util_prog replace start -Bf 1 $SPARE_DEV $SCRATCH_MNT
+
+# Unmount to drop all cache so next read will read from disk
+_scratch_unmount
+_mount $SPARE_DEV $SCRATCH_MNT
+
+# Now the EXTENT_DATA item still marks the extent as compressed,
+# but the on-disk data is uncompressed, thus reading it as compressed
+# will definitely cause EIO.
+cat $SCRATCH_MNT/nodatasum_file > /dev/null
+
+_scratch_unmount
+_spare_dev_put
+_scratch_dev_pool_put
+
+echo "Silence is golden"
+# success, all done
+status=0
+exit
diff --git a/tests/btrfs/161.out b/tests/btrfs/161.out
new file mode 100644
index 00000000..1752a243
--- /dev/null
+++ b/tests/btrfs/161.out
@@ -0,0 +1,2 @@
+QA output created by 161
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index f04ee8d5..9195b368 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -163,3 +163,4 @@
158 auto quick raid scrub
159 auto quick
160 auto quick
+161 auto quick replace volume
--
2.17.0
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