block: remove QUEUE_FLAG_DISCARD

Just use a non-zero max_discard_sectors as an indicator for discard
support, similar to what is done for write zeroes.

The only places where needs special attention is the RAID5 driver,
which must clear discard support for security reasons by default,
even if the default stacking rules would allow for it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> [drbd]
Acked-by: Jan Höppner <hoeppner@linux.ibm.com> [s390]
Acked-by: Coly Li <colyli@suse.de> [bcache]
Acked-by: David Sterba <dsterba@suse.com> [btrfs]
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220415045258.199825-25-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 4 insertions, 20 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 7b501c8d5992..912560f611c3 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -942,7 +942,7 @@ int drbd_send_sizes(struct drbd_peer_device *peer_device, int trigger_reply, enu
 			cpu_to_be32(bdev_alignment_offset(bdev));
 		p->qlim->io_min = cpu_to_be32(bdev_io_min(bdev));
 		p->qlim->io_opt = cpu_to_be32(bdev_io_opt(bdev));
-		p->qlim->discard_enabled = blk_queue_discard(q);
+		p->qlim->discard_enabled = !!bdev_max_discard_sectors(bdev);
 		put_ldev(device);
 	} else {
 		struct request_queue *q = device->rq_queue;
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index a0a06e238e91..0678ceb50579 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1210,7 +1210,7 @@ static void decide_on_discard_support(struct drbd_device *device,
 		first_peer_device(device)->connection;
 	struct request_queue *q = device->rq_queue;
 
-	if (bdev && !blk_queue_discard(bdev->backing_bdev->bd_disk->queue))
+	if (bdev && !bdev_max_discard_sectors(bdev->backing_bdev))
 		goto not_supported;
 
 	if (connection->cstate >= C_CONNECTED &&
@@ -1230,30 +1230,16 @@ static void decide_on_discard_support(struct drbd_device *device,
 	 */
 	blk_queue_discard_granularity(q, 512);
 	q->limits.max_discard_sectors = drbd_max_discard_sectors(connection);
-	blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 	q->limits.max_write_zeroes_sectors =
 		drbd_max_discard_sectors(connection);
 	return;
 
 not_supported:
-	blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
 	blk_queue_discard_granularity(q, 0);
 	q->limits.max_discard_sectors = 0;
 	q->limits.max_write_zeroes_sectors = 0;
 }
 
-static void fixup_discard_if_not_supported(struct request_queue *q)
-{
-	/* To avoid confusion, if this queue does not support discard, clear
-	 * max_discard_sectors, which is what lsblk -D reports to the user.
-	 * Older kernels got this wrong in "stack limits".
-	 * */
-	if (!blk_queue_discard(q)) {
-		blk_queue_max_discard_sectors(q, 0);
-		blk_queue_discard_granularity(q, 0);
-	}
-}
-
 static void fixup_write_zeroes(struct drbd_device *device, struct request_queue *q)
 {
 	/* Fixup max_write_zeroes_sectors after blk_stack_limits():
@@ -1300,7 +1286,6 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
 		blk_stack_limits(&q->limits, &b->limits, 0);
 		disk_update_readahead(device->vdisk);
 	}
-	fixup_discard_if_not_supported(q);
 	fixup_write_zeroes(device, q);
 }
 
@@ -1447,7 +1432,7 @@ static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *dis
 	if (disk_conf->al_extents > drbd_al_extents_max(nbc))
 		disk_conf->al_extents = drbd_al_extents_max(nbc);
 
-	if (!blk_queue_discard(q)) {
+	if (!bdev_max_discard_sectors(bdev)) {
 		if (disk_conf->rs_discard_granularity) {
 			disk_conf->rs_discard_granularity = 0; /* disable feature */
 			drbd_info(device, "rs_discard_granularity feature disabled\n");
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 0b4c7de46398..8a4a47da56fe 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1575,11 +1575,10 @@ int drbd_issue_discard_or_zero_out(struct drbd_device *device, sector_t start, u
 
 static bool can_do_reliable_discards(struct drbd_device *device)
 {
-	struct request_queue *q = bdev_get_queue(device->ldev->backing_bdev);
 	struct disk_conf *dc;
 	bool can_do;
 
-	if (!blk_queue_discard(q))
+	if (!bdev_max_discard_sectors(device->ldev->backing_bdev))
 		return false;
 
 	rcu_read_lock();