[PATCH] xfs/014: try a few times to create speculative preallocations

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

This test checks that speculative file preallocations are transferred to
threads writing other files when space is low.  Since we have background
threads to clear those preallocations, it's possible that the test
program might not get a speculative preallocation on the first try.

This problem has become more pronounced since the introduction of
background inode inactivation since userspace no longer has direct
control over the timing of file blocks being released from unlinked
files.  As a result, the author has seen an increase in sporadic
warnings from this test about speculative preallocations not appearing.

Therefore, modify the function to try up to five times to create the
speculative preallocation before emitting warnings that then cause
golden output failures.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 tests/xfs/014 |   41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/tests/xfs/014 b/tests/xfs/014
index a605b359..1f0ebac3 100755
--- a/tests/xfs/014
+++ b/tests/xfs/014
@@ -33,27 +33,36 @@ _cleanup()
 # failure.
 _spec_prealloc_file()
 {
-	file=$1
+	local file=$1
+	local prealloc_size=0
+	local i=0
 
-	rm -f $file
+	# Now that we have background garbage collection processes that can be
+	# triggered by low space/quota conditions, it's possible that we won't
+	# succeed in creating a speculative preallocation on the first try.
+	for ((tries = 0; tries < 5 && prealloc_size == 0; tries++)); do
+		rm -f $file
 
-	# a few file extending open-write-close cycles should be enough to
-	# trigger the fs to retain preallocation. write 256k in 32k intervals to
-	# be sure
-	for i in $(seq 0 32768 262144); do
-		$XFS_IO_PROG -f -c "pwrite $i 32k" $file >> $seqres.full
+		# a few file extending open-write-close cycles should be enough
+		# to trigger the fs to retain preallocation. write 256k in 32k
+		# intervals to be sure
+		for i in $(seq 0 32768 262144); do
+			$XFS_IO_PROG -f -c "pwrite $i 32k" $file >> $seqres.full
+		done
+
+		# write a 4k aligned amount of data to keep the calculations
+		# simple
+		$XFS_IO_PROG -c "pwrite 0 128m" $file >> $seqres.full
+
+		size=`_get_filesize $file`
+		blocks=`stat -c "%b" $file`
+		blocksize=`stat -c "%B" $file`
+
+		prealloc_size=$((blocks * blocksize - size))
 	done
 
-	# write a 4k aligned amount of data to keep the calculations simple
-	$XFS_IO_PROG -c "pwrite 0 128m" $file >> $seqres.full
-
-	size=`_get_filesize $file`
-	blocks=`stat -c "%b" $file`
-	blocksize=`stat -c "%B" $file`
-
-	prealloc_size=$((blocks * blocksize - size))
 	if [ $prealloc_size -eq 0 ]; then
-		echo "Warning: No speculative preallocation for $file." \
+		echo "Warning: No speculative preallocation for $file after $tries iterations." \
 			"Check use of the allocsize= mount option."
 	fi