ZTS: Remove ashift setting from dedup_quota test (#17250)

The test writes 1M of 1KB blocks, which may produce up to 1GB of
dirty data.  On top of that ashift=12 likely produces additional
4GB of ZIO buffers during sync process.  On top of that we likely
need some page cache since the pool reside on files.  And finally
we need to cache the DDT.  Not surprising that the test regularly
ends up in OOMs, possibly depending on TXG size variations.

Also replace fio with pretty strange parameter set with a set of
dd writes and TXG commits, just as we neeed here.

While here, remove compression.  It has nothing to do here, but
waste CI CPU time.

Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Tony Hutter <[email protected]>
(cherry picked from commit 1d8f625)

Author: amotin

tests/zfs-tests/tests/functional/dedup/dedup_quota.ksh

@@ -76,7 +76,7 @@ function do_setup
 {
 	log_must truncate -s 5G $VDEV_GENERAL
 	# Use 'xattr=sa' to prevent selinux xattrs influencing our accounting
-	log_must zpool create -o ashift=12 -f -O xattr=sa -m $MOUNTDIR $POOL $VDEV_GENERAL
+	log_must zpool create -f -O xattr=sa -m $MOUNTDIR $POOL $VDEV_GENERAL
 	log_must zfs set compression=off dedup=on $POOL
 }
 
@@ -186,31 +186,30 @@ function ddt_dedup_vdev_limit
 	# add a dedicated dedup/special VDEV and enable an automatic quota
 	if (( RANDOM % 2 == 0 )) ; then
 		class="special"
+		size="200M"
 	else
 		class="dedup"
+		size="100M"
 	fi
-	log_must truncate -s 200M $VDEV_DEDUP
+	log_must truncate -s $size $VDEV_DEDUP
 	log_must zpool add $POOL $class $VDEV_DEDUP
 	log_must zpool set dedup_table_quota=auto $POOL
 
 	log_must zfs set recordsize=1K $POOL
-	log_must zfs set compression=zstd $POOL
 
 	# Generate a working set to fill up the dedup/special allocation class
-	log_must fio --directory=$MOUNTDIR --name=dedup-filler-1 \
-		--rw=read --bs=1m --numjobs=2 --iodepth=8 \
-		--size=512M --end_fsync=1 --ioengine=posixaio --runtime=1 \
-		--group_reporting --fallocate=none --output-format=terse \
-		--dedupe_percentage=0
-	log_must sync_pool $POOL
+	for i in {0..63}; do
+		log_must dd if=/dev/urandom of=$MOUNTDIR/file${i} bs=1M count=16
+		log_must sync_pool $POOL
+	done
 
 	zpool status -D $POOL
 	zpool list -v $POOL
 	echo DDT size $(dedup_table_size), with $(ddt_entries) entries
 
 	#
-	# With no DDT quota in place, the above workload will produce over
-	# 800,000 entries by using space in the normal class. With a quota, it
+	# With no DDT quota in place, the above workload will produce up to
+	# 1M of entries by using space in the normal class. With a quota, it
 	# should be well under 500,000. However, logged entries are hard to
 	# account for because they can appear on both logs, and can also
 	# represent an eventual removal. This isn't easily visible from