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>

13 files changed, 10 insertions, 45 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();
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 8d800d46e498..0e061c9896ef 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -314,15 +314,12 @@ static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
 
 	mode |= FALLOC_FL_KEEP_SIZE;
 
-	if (!blk_queue_discard(lo->lo_queue)) {
-		ret = -EOPNOTSUPP;
-		goto out;
-	}
+	if (!bdev_max_discard_sectors(lo->lo_device))
+		return -EOPNOTSUPP;
 
 	ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
 	if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
-		ret = -EIO;
- out:
+		return -EIO;
 	return ret;
 }
 
@@ -787,12 +784,10 @@ static void loop_config_discard(struct loop_device *lo)
 		q->limits.discard_granularity = granularity;
 		blk_queue_max_discard_sectors(q, max_discard_sectors);
 		blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 	} else {
 		q->limits.discard_granularity = 0;
 		blk_queue_max_discard_sectors(q, 0);
 		blk_queue_max_write_zeroes_sectors(q, 0);
-		blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
 	}
 	q->limits.discard_alignment = 0;
 }
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 5a1f98494ddd..4729aef8c646 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1231,8 +1231,6 @@ static void nbd_parse_flags(struct nbd_device *nbd)
 		set_disk_ro(nbd->disk, true);
 	else
 		set_disk_ro(nbd->disk, false);
-	if (config->flags & NBD_FLAG_SEND_TRIM)
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 	if (config->flags & NBD_FLAG_SEND_FLUSH) {
 		if (config->flags & NBD_FLAG_SEND_FUA)
 			blk_queue_write_cache(nbd->disk->queue, true, true);
@@ -1319,8 +1317,7 @@ static void nbd_config_put(struct nbd_device *nbd)
 		nbd->tag_set.timeout = 0;
 		nbd->disk->queue->limits.discard_granularity = 0;
 		nbd->disk->queue->limits.discard_alignment = 0;
-		blk_queue_max_discard_sectors(nbd->disk->queue, UINT_MAX);
-		blk_queue_flag_clear(QUEUE_FLAG_DISCARD, nbd->disk->queue);
+		blk_queue_max_discard_sectors(nbd->disk->queue, 0);
 
 		mutex_unlock(&nbd->config_lock);
 		nbd_put(nbd);
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index c441a4972064..5cb4c92cdffe 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1767,7 +1767,6 @@ static void null_config_discard(struct nullb *nullb)
 	nullb->q->limits.discard_granularity = nullb->dev->blocksize;
 	nullb->q->limits.discard_alignment = nullb->dev->blocksize;
 	blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
-	blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
 }
 
 static const struct block_device_operations null_bio_ops = {
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index b844432bad20..2b21f717cce1 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4942,7 +4942,6 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
 	blk_queue_io_opt(q, rbd_dev->opts->alloc_size);
 
 	if (rbd_dev->opts->trim) {
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 		q->limits.discard_granularity = rbd_dev->opts->alloc_size;
 		blk_queue_max_discard_sectors(q, objset_bytes >> SECTOR_SHIFT);
 		blk_queue_max_write_zeroes_sectors(q, objset_bytes >> SECTOR_SHIFT);
diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
index b66e8840b94b..efa99a388450 100644
--- a/drivers/block/rnbd/rnbd-clt.c
+++ b/drivers/block/rnbd/rnbd-clt.c
@@ -1364,8 +1364,6 @@ static void setup_request_queue(struct rnbd_clt_dev *dev)
 	blk_queue_max_discard_sectors(dev->queue, dev->max_discard_sectors);
 	dev->queue->limits.discard_granularity	= dev->discard_granularity;
 	dev->queue->limits.discard_alignment	= dev->discard_alignment;
-	if (dev->max_discard_sectors)
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, dev->queue);
 	if (dev->secure_discard)
 		blk_queue_flag_set(QUEUE_FLAG_SECERASE, dev->queue);
 
diff --git a/drivers/block/rnbd/rnbd-srv-dev.h b/drivers/block/rnbd/rnbd-srv-dev.h
index f82fbb4bbda8..1f7e1c8fd4d9 100644
--- a/drivers/block/rnbd/rnbd-srv-dev.h
+++ b/drivers/block/rnbd/rnbd-srv-dev.h
@@ -49,9 +49,6 @@ static inline int rnbd_dev_get_secure_discard(const struct rnbd_dev *dev)
 
 static inline int rnbd_dev_get_max_discard_sects(const struct rnbd_dev *dev)
 {
-	if (!blk_queue_discard(bdev_get_queue(dev->bdev)))
-		return 0;
-
 	return bdev_max_discard_sectors(dev->bdev);
 }
 
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index a8bcf3f664af..6ccf15253dee 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -888,8 +888,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 			v = sg_elems;
 		blk_queue_max_discard_segments(q,
 					       min(v, MAX_DISCARD_SEGMENTS));
-
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 	}
 
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_WRITE_ZEROES)) {
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 8b691fe50475..83cd08041e6b 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -583,7 +583,7 @@ static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info
 	if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 		return;
 
-	if (blk_queue_discard(q)) {
+	if (bdev_max_discard_sectors(bdev)) {
 		err = xenbus_printf(xbt, dev->nodename,
 			"discard-granularity", "%u",
 			q->limits.discard_granularity);
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 003056d4f7f5..e13cb4d48f1e 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -944,7 +944,6 @@ static void blkif_set_queue_limits(struct blkfront_info *info)
 	blk_queue_flag_set(QUEUE_FLAG_VIRT, rq);
 
 	if (info->feature_discard) {
-		blk_queue_flag_set(QUEUE_FLAG_DISCARD, rq);
 		blk_queue_max_discard_sectors(rq, get_capacity(gd));
 		rq->limits.discard_granularity = info->discard_granularity ?:
 						 info->physical_sector_size;
@@ -1606,7 +1605,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 				blkif_req(req)->error = BLK_STS_NOTSUPP;
 				info->feature_discard = 0;
 				info->feature_secdiscard = 0;
-				blk_queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
+				blk_queue_max_discard_sectors(rq, 0);
 				blk_queue_flag_clear(QUEUE_FLAG_SECERASE, rq);
 			}
 			break;
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index e9474b02012d..59ff444bf6c7 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1952,7 +1952,6 @@ static int zram_add(void)
 	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 	zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
 	blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
-	blk_queue_flag_set(QUEUE_FLAG_DISCARD, zram->disk->queue);
 
 	/*
 	 * zram_bio_discard() will clear all logical blocks if logical block