xfstests: test speculative preallocation reclaim on ENOSPC/EDQUOT

XFS can allocate significant amounts of space to files via speculative
preallocation. Such preallocation may not be reclaimed automatically on
file close() if a file is repeatedly opened and extended. For smaller
filesystems with relatively large and slow growing files, this
preallocation can linger for some time, including contributing to out of
space conditions.

Create a situation where an fs is near out of space while several files
still have lingering, significant preallocations. Verify that new
writers reclaim the preallocated space rather than return ENOSPC. Repeat
a similar test for quota limits and EDQUOT.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/xfs/014

@@ -0,0 +1,200 @@
+#!/bin/bash
+# FS QA Test No. xfs/014
+#
+# Test the behavior of XFS dynamic speculative preallocation at ENOSPC and
+# EDQUOT conditions. Speculative preallocation allocates post-EOF space to files
+# as they are extended. This test creates conditions where an fs is near a space
+# limit with lingering, relatively significant preallocations and verifies that
+# new writers reclaim said preallocations rather than prematurely fail with
+# ENOSPC/EDQUOT.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2014 Red Hat, Inc.  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!
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/quota
+
+_cleanup()
+{
+	cd /
+	umount $LOOP_MNT 2>/dev/null
+	umount $SCRATCH_MNT 2>/dev/null
+	rm -f $tmp.*
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# Create a file using a repeated open, extending write and close pattern. This
+# causes the preallocation to persist after the file is closed. Preallocation
+# will not be reclaimed unless the inode is evicted or we hit an allocation
+# failure.
+_spec_prealloc_file()
+{
+	file=$1
+
+	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
+	done
+
+	# write a 4k aligned amount of data to keep the calculations simple
+	$XFS_IO_PROG -c "pwrite 0 128m" $file >> $seqres.full
+
+	size=`stat -c "%s" $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 $file." \
+			"Check use of the allocsize= mount option."
+	fi
+
+	# keep a running total of how much preallocation we've created
+	TOTAL_PREALLOC=$((TOTAL_PREALLOC + prealloc_size))
+}
+
+_consume_free_space()
+{
+	dir=$1
+
+	# allocate all but 10MB of available space
+	freesp=`df -m $dir | awk '/^\// { print $4 - 10 }'`
+	$XFS_IO_PROG -f -c "falloc 0 ${freesp}M" $dir/spc
+}
+
+# Create several files with preallocation and consume the remaining free space
+# via fallocate to the put the fs at ENOSPC. Create a set of background writers
+# to write into ENOSPC and cause the preallocation to be reclaimed and
+# reallocated to the new writers.
+_test_enospc()
+{
+	dir=$1
+
+	rm -rf $dir/*
+
+	TOTAL_PREALLOC=0
+	for i in $(seq 0 3); do
+		_spec_prealloc_file $dir/pre$i
+	done
+
+	_consume_free_space $dir
+
+	# consume 1/2 of the current preallocation across the set of 4 writers
+	write_size=$((TOTAL_PREALLOC / 2 / 4))
+	for i in $(seq 0 3); do
+		$XFS_IO_PROG -f -c "pwrite 0 $write_size" $dir/file.$i \
+			>> $seqres.full &
+	done
+
+	wait
+}
+
+# Create preallocations accounted by both user and group quotas. Set the
+# associated quota hard limits to put them at EDQUOT. Verify that a new writer
+# reclaims the preallocated space and proceeds without error.
+_test_edquot()
+{
+	dir=$1
+
+	rm -rf $dir/*
+
+	TOTAL_PREALLOC=0
+	_spec_prealloc_file $dir/user
+	chown $qa_user $dir/user
+
+	_spec_prealloc_file $dir/group
+	chgrp $qa_group $dir/group
+
+	# writing to a file under both quotas means both will be reclaimed on
+	# allocation failure
+	touch $dir/file
+	chown $qa_user $dir/file
+	chgrp $qa_group $dir/file
+
+	# put both quotas at EDQUOT
+	blks=`$XFS_QUOTA_PROG -xc "quota -u $qa_user" $dir | \
+		tail -n 1 | awk '{ print $2 }'`
+	$XFS_QUOTA_PROG -xc "limit -u bhard=${blks}k $qa_user" $dir
+	blks=`$XFS_QUOTA_PROG -xc "quota -g $qa_grup" $dir | \
+		tail -n 1 | awk '{ print $2 }'`
+	$XFS_QUOTA_PROG -xc "limit -g bhard=${blks}k $qa_group" $dir
+
+	# each quota has a single file worth of preallocation to reclaim. leave
+	# some wiggle room and write to 1/3 the total.
+	write_size=$((TOTAL_PREALLOC / 3))
+	$XFS_IO_PROG -c "pwrite 0 $write_size" $dir/file >> $seqres.full
+}
+
+# real QA test starts here
+_supported_fs xfs
+_supported_os Linux
+
+_require_scratch
+_require_xfs_io_command "falloc"
+_require_loop
+_require_quota
+_require_user
+_require_group
+
+rm -f $seqres.full
+
+echo "Silence is golden."
+
+_scratch_mkfs_xfs >> $seqres.full 2>&1
+_scratch_mount
+
+# make sure the background eofblocks scanner doesn't interfere
+orig_sp_time=`cat /proc/sys/fs/xfs/speculative_prealloc_lifetime`
+echo 9999 > /proc/sys/fs/xfs/speculative_prealloc_lifetime
+
+LOOP_FILE=$SCRATCH_MNT/$seq.fs
+LOOP_MNT=$SCRATCH_MNT/$seq.mnt
+
+$MKFS_XFS_PROG -d "file=1,name=$LOOP_FILE,size=10g" >> $seqres.full 2>&1
+
+mkdir -p $LOOP_MNT
+mount -t xfs -o loop,uquota,gquota $LOOP_FILE $LOOP_MNT || \
+	_fail "Failed to mount loop fs."
+
+_test_enospc $LOOP_MNT
+_test_edquot $LOOP_MNT
+
+umount $LOOP_MNT
+
+echo $orig_sp_time > /proc/sys/fs/xfs/speculative_prealloc_lifetime
+
+umount $SCRATCH_MNT
+_check_scratch_fs
+
+status=0
+exit

tests/xfs/014.out

@@ -0,0 +1,2 @@
+QA output created by 014
+Silence is golden.

tests/xfs/group

@@ -10,6 +10,7 @@
 010 auto quick repair
 012 rw auto quick
 013 auto metadata stress
+014 auto enospc quick quota
 016 rw auto quick
 017 mount auto quick stress
 018 deprecated # log logprint v2log