tony feedback

Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>

Author: pcd1193182

man/man4/zfs.4

@@ -457,6 +457,11 @@ because user pages can be placed under write protection in
 .Fx
 before the Direct I/O write is issued.
 .
+.It Sy zfs_vdev_large_label_min_size Ns = Ns Sy 1000000000000 Pq uint
+Minimum device size to use the large label format, if the feature is enabled.
+Note that disks that are too small to store the large label (less than about
+1084MiB) will not use it, regardless of the value of this tunable.
+.
 .It Sy zfs_vdev_min_auto_ashift Ns = Ns Sy ASHIFT_MIN Po 9 Pc Pq uint
 Minimum ashift used when creating new top-level vdevs.
 .

man/man7/zpool-features.7

@@ -738,7 +738,10 @@ However, because uberblocks always take at least one disk sector, large disk
 sectors result in unacceptably small uberblock rings.
 The new label format is 256MiB in size, with 128KiB reserved for the expanded
 uberblock ring.
-When enabled, the new larger size will be used on sufficiently large disks.
+When enabled, the new larger size will be used on disks of at least 1TB (by
+default, controlled by the
+.Sy zfs_vdev_large_label_min_size
+tunable).
 .Pp
 This feature becomes active when a large label is written to any of the disks
 in the pool.

module/zfs/vdev.c

@@ -100,7 +100,7 @@ static uint_t zfs_vdev_default_ms_shift = 29;
 /* upper limit for metaslab size (16G) */
 static uint_t zfs_vdev_max_ms_shift = 34;
 
-uint64_t zfs_vdev_large_label_min_size = 1ULL << 40;
+uint64_t zfs_vdev_large_label_min_size = 1000ULL * 1000 * 1000 * 1000;
 
 static int vdev_validate_skip = B_FALSE;
 
@@ -2289,7 +2289,9 @@ vdev_open(vdev_t *vd)
 	    spa->spa_create_large_label_ok))
 		large_label = B_FALSE;
 	else if (vd->vdev_asize == 0 && vd->vdev_ops->vdev_op_leaf)
-		large_label = osize > zfs_vdev_large_label_min_size;
+		large_label = (osize > zfs_vdev_large_label_min_size) &&
+		    (osize > SPA_MINDEVSIZE + (VDEV_LARGE_LABEL_SIZE -
+		    sizeof (vdev_label_t)) * VDEV_LABELS);
 	else
 		large_label = vd->vdev_large_label;
 	uint64_t align;

tests/zfs-tests/include/tunables.cfg

@@ -45,6 +45,7 @@ EMBEDDED_SLOG_MIN_MS		embedded_slog_min_ms		zfs_embedded_slog_min_ms
 INITIALIZE_CHUNK_SIZE		initialize_chunk_size		zfs_initialize_chunk_size
 INITIALIZE_VALUE		initialize_value		zfs_initialize_value
 KEEP_LOG_SPACEMAPS_AT_EXPORT	keep_log_spacemaps_at_export	zfs_keep_log_spacemaps_at_export
+LARGE_LABEL_MIN_SIZE		vdev.large_label_min_size	zfs_vdev_large_label_min_size
 LUA_MAX_MEMLIMIT		lua.max_memlimit		zfs_lua_max_memlimit
 L2ARC_MFUONLY			l2arc.mfuonly			l2arc_mfuonly
 L2ARC_NOPREFETCH		l2arc.noprefetch		l2arc_noprefetch

tests/zfs-tests/tests/functional/large_label/large_label_001_pos.ksh

@@ -36,11 +36,14 @@
 function cleanup {
 	log_pos zpool destroy $TESTPOOL
 	log_must rm $mntpnt/dsk*
+	log_must restore_tunable LARGE_LABEL_MIN_SIZE
 }
 
 log_assert "Verify that new label works for basic pool operation"
 log_onexit cleanup
 
+log_must save_tunable LARGE_LABEL_MIN_SIZE
+
 mntpnt="$TESTDIR1"
 log_must truncate -s 2T $mntpnt/dsk0
 
@@ -51,5 +54,14 @@ log_must create_pool -f $TESTPOOL "$DSK"0
 log_must zdb -l "$DSK"0
 log_must uses_large_label "$DSK"0
 log_mustnot uses_old_label "$DSK"0
+log_must destroy_pool $TESTPOOL
+
+log_must set_tunable64 LARGE_LABEL_MIN_SIZE 1
+log_must truncate -s 64M $mntpnt/dsk1
+
+log_must create_pool -f $TESTPOOL "$DSK"1
+log_must zdb -l "$DSK"1
+log_mustnot uses_large_label "$DSK"1
+log_must uses_old_label "$DSK"1
 
 log_pass "New label works for basic pool operation"

tests/zfs-tests/tests/functional/large_label/large_label_002_pos.ksh

@@ -49,7 +49,7 @@ DSK="$mntpnt/dsk"
 
 log_must create_pool -f $TESTPOOL "$DSK"0 mirror "$DSK"1 "$DSK"2 raidz1 "$DSK"3 "$DSK"4 "$DSK"5 log "$DSK"6 special "$DSK"7
 
-log_must dd if=/dev/urandom of=/$TESTPOOL/f1 bs=1M count=1k
+log_must file_write -o create -d 'R' -f /$TESTPOOL/f1 -b 1M -c 1k
 log_must sync_pool $TESTPOOL
 
 for i in `seq 0 7`; do

tests/zfs-tests/tests/functional/large_label/large_label_mirror.ksh

@@ -48,7 +48,7 @@ log_must truncate -s 2G $mntpnt/small1
 
 log_must create_pool -f $TESTPOOL $mntpnt/small1
 log_must zfs create $TESTPOOL/fs
-log_must dd if=/dev/urandom of=/$TESTPOOL/fs/f1 bs=1M count=16
+log_must file_write -o create -d 'R' -f /$TESTPOOL/fs/f1 -b 1M -c 16
 log_must touch /$TESTPOOL/f2
 
 log_must sync_pool $TESTPOOL