[PATCH] common/xfs: Execute _xfs_check only when explicitly asked

[Chandan Rajendra <chandanrlinux@gmail.com>]

fsstress when executed as part of some of the tests (e.g. generic/270)
invokes chown() syscall many times by passing random integers as value
for the uid argument. For each such syscall invocation for which there
is no on-disk quota block, xfs invokes xfs_dquot_disk_alloc() which
allocates a new block and instantiates all the quota structures mapped
by the newly allocated block. For filesystems with 64k block size, the
number of on-disk quota structures created will be 16 times more than
that for a filesystem with 4k block size.

xfs_db's check command (executed after test script finishes execution)
will try to read in all of the on-disk quota structures into
memory. This causes the OOM event to be triggered when reading from
filesystems with 64k block size. For filesystems with sufficiently large
amount of system memory, this causes the test to execute for a very long
time.

Due to the above stated reasons, this commit disables execution of
xfs_db's check command unless explictly asked by the user by setting
$EXECUTE_XFS_DB_CHECK variable.

Signed-off-by: Chandan Rajendra <chandanrlinux@gmail.com>
---
 README     |  2 ++
 common/xfs | 17 +++++++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/README b/README
index 094a7742..c47569cd 100644
--- a/README
+++ b/README
@@ -88,6 +88,8 @@ Preparing system for tests:
                run xfs_repair -n to check the filesystem; xfs_repair to rebuild
                metadata indexes; and xfs_repair -n (a third time) to check the
                results of the rebuilding.
+	     - set EXECUTE_XFS_DB_CHECK=1 to have _check_xfs_filesystem
+               run xfs_db's check command on the filesystem.
              - xfs_scrub, if present, will always check the test and scratch
                filesystems if they are still online at the end of the test.
                It is no longer necessary to set TEST_XFS_SCRUB.
diff --git a/common/xfs b/common/xfs
index d9a9784f..93ebab75 100644
--- a/common/xfs
+++ b/common/xfs
@@ -455,10 +455,19 @@ _check_xfs_filesystem()
 		ok=0
 	fi
 
-	# xfs_check runs out of memory on large files, so even providing the test
-	# option (-t) to avoid indexing the free space trees doesn't make it pass on
-	# large filesystems. Avoid it.
-	if [ "$LARGE_SCRATCH_DEV" != yes ]; then
+	dbsize="$($XFS_INFO_PROG "${device}" | grep data.*bsize | sed -e 's/^.*bsize=//g' -e 's/\([0-9]*\).*$/\1/g')"
+
+	# xfs_check runs out of memory,
+	# 1. On large files. So even providing the test option (-t) to
+	# avoid indexing the free space trees doesn't make it pass on
+	# large filesystems.
+	# 2. When checking filesystems with large number of quota
+	# structures. This case happens consistently with 64k blocksize when
+	# creating large number of on-disk quota structures whose quota ids
+	# are spread across a large integer range.
+	#
+	# Hence avoid executing it unless explicitly asked by user.
+	if [ -n "$EXECUTE_XFS_DB_CHECK" -a "$LARGE_SCRATCH_DEV" != yes ]; then
 		_xfs_check $extra_log_options $device 2>&1 > $tmp.fs_check
 	fi
 	if [ -s $tmp.fs_check ]; then
-- 
2.19.1