drbd atomic queue limits conversion

drbd atomic queue limits conversion

[Christoph Hellwig]

Hi Jens,

this is a standalone resend of the drbd queue limits conversion.
Philipp said Linbit has reviewed and tested it, and they'll hopefully
provide the formal tags for that in a bit.

Diffstat:
 drbd_main.c |   13 ++-
 drbd_nl.c   |  210 ++++++++++++++++++++++++++++--------------------------------
 2 files changed, 110 insertions(+), 113 deletions(-)

[PATCH 1/7] drbd: pass the max_hw_sectors limit to blk_alloc_disk

[Christoph Hellwig]

Pass a queue_limits structure with the max_hw_sectors limit to
blk_alloc_disk instead of updating the limit on the allocated gendisk.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_main.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index cea1e537fd56c1..113b441d4d3670 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2690,6 +2690,14 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	int id;
 	int vnr = adm_ctx->volume;
 	enum drbd_ret_code err = ERR_NOMEM;
+	struct queue_limits lim = {
+		/*
+		 * Setting the max_hw_sectors to an odd value of 8kibyte here.
+		 * This triggers a max_bio_size message upon first attach or
+		 * connect.
+		 */
+		.max_hw_sectors		= DRBD_MAX_BIO_SIZE_SAFE >> 8,
+	};
 
 	device = minor_to_device(minor);
 	if (device)
@@ -2708,7 +2716,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 
 	drbd_init_set_defaults(device);
 
-	disk = blk_alloc_disk(NULL, NUMA_NO_NODE);
+	disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
 	if (IS_ERR(disk)) {
 		err = PTR_ERR(disk);
 		goto out_no_disk;
@@ -2729,9 +2737,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 
 	blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, disk->queue);
 	blk_queue_write_cache(disk->queue, true, true);
-	/* Setting the max_hw_sectors to an odd value of 8kibyte here
-	   This triggers a max_bio_size message upon first attach or connect */
-	blk_queue_max_hw_sectors(disk->queue, DRBD_MAX_BIO_SIZE_SAFE >> 8);
 
 	device->md_io.page = alloc_page(GFP_KERNEL);
 	if (!device->md_io.page)
-- 
2.39.2

[PATCH 2/7] drbd: refactor drbd_reconsider_queue_parameters

[Christoph Hellwig]

Split out a drbd_max_peer_bio_size helper for the peer I/O size,
and condense the various checks to a nested min3(..., max())) instead
of using a lot of local variables.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 84 +++++++++++++++++++++---------------
 1 file changed, 49 insertions(+), 35 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 43747a1aae4353..9135001a8e572d 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1189,6 +1189,33 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
 	return 0;
 }
 
+static unsigned int drbd_max_peer_bio_size(struct drbd_device *device)
+{
+	/*
+	 * We may ignore peer limits if the peer is modern enough.  From 8.3.8
+	 * onwards the peer can use multiple BIOs for a single peer_request.
+	 */
+	if (device->state.conn < C_WF_REPORT_PARAMS)
+		return device->peer_max_bio_size;
+
+	if (first_peer_device(device)->connection->agreed_pro_version < 94)
+		return min(device->peer_max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
+
+	/*
+	 * Correct old drbd (up to 8.3.7) if it believes it can do more than
+	 * 32KiB.
+	 */
+	if (first_peer_device(device)->connection->agreed_pro_version == 94)
+		return DRBD_MAX_SIZE_H80_PACKET;
+
+	/*
+	 * drbd 8.3.8 onwards, before 8.4.0
+	 */
+	if (first_peer_device(device)->connection->agreed_pro_version < 100)
+		return DRBD_MAX_BIO_SIZE_P95;
+	return DRBD_MAX_BIO_SIZE;
+}
+
 static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
 {
 	q->limits.discard_granularity = granularity;
@@ -1303,48 +1330,35 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
 	fixup_discard_support(device, q);
 }
 
-void drbd_reconsider_queue_parameters(struct drbd_device *device, struct drbd_backing_dev *bdev, struct o_qlim *o)
+void drbd_reconsider_queue_parameters(struct drbd_device *device,
+		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
-	unsigned int now, new, local, peer;
-
-	now = queue_max_hw_sectors(device->rq_queue) << 9;
-	local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
-	peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */
+	unsigned int now = queue_max_hw_sectors(device->rq_queue) <<
+			SECTOR_SHIFT;
+	unsigned int new;
 
 	if (bdev) {
-		local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
-		device->local_max_bio_size = local;
-	}
-	local = min(local, DRBD_MAX_BIO_SIZE);
-
-	/* We may ignore peer limits if the peer is modern enough.
-	   Because new from 8.3.8 onwards the peer can use multiple
-	   BIOs for a single peer_request */
-	if (device->state.conn >= C_WF_REPORT_PARAMS) {
-		if (first_peer_device(device)->connection->agreed_pro_version < 94)
-			peer = min(device->peer_max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
-			/* Correct old drbd (up to 8.3.7) if it believes it can do more than 32KiB */
-		else if (first_peer_device(device)->connection->agreed_pro_version == 94)
-			peer = DRBD_MAX_SIZE_H80_PACKET;
-		else if (first_peer_device(device)->connection->agreed_pro_version < 100)
-			peer = DRBD_MAX_BIO_SIZE_P95;  /* drbd 8.3.8 onwards, before 8.4.0 */
-		else
-			peer = DRBD_MAX_BIO_SIZE;
+		struct request_queue *b = bdev->backing_bdev->bd_disk->queue;
 
-		/* We may later detach and re-attach on a disconnected Primary.
-		 * Avoid this setting to jump back in that case.
-		 * We want to store what we know the peer DRBD can handle,
-		 * not what the peer IO backend can handle. */
-		if (peer > device->peer_max_bio_size)
-			device->peer_max_bio_size = peer;
+		device->local_max_bio_size =
+			queue_max_hw_sectors(b) << SECTOR_SHIFT;
 	}
-	new = min(local, peer);
 
-	if (device->state.role == R_PRIMARY && new < now)
-		drbd_err(device, "ASSERT FAILED new < now; (%u < %u)\n", new, now);
-
-	if (new != now)
+	/*
+	 * We may later detach and re-attach on a disconnected Primary.  Avoid
+	 * decreasing the value in this case.
+	 *
+	 * We want to store what we know the peer DRBD can handle, not what the
+	 * peer IO backend can handle.
+	 */
+	new = min3(DRBD_MAX_BIO_SIZE, device->local_max_bio_size,
+		max(drbd_max_peer_bio_size(device), device->peer_max_bio_size));
+	if (new != now) {
+		if (device->state.role == R_PRIMARY && new < now)
+			drbd_err(device, "ASSERT FAILED new < now; (%u < %u)\n",
+					new, now);
 		drbd_info(device, "max BIO size = %u\n", new);
+	}
 
 	drbd_setup_queue_param(device, bdev, new, o);
 }
-- 
2.39.2

[PATCH 3/7] drbd: refactor the backing dev max_segments calculation

[Christoph Hellwig]

Factor out a drbd_backing_dev_max_segments helper that checks the
backing device limitation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 9135001a8e572d..0326b7322ceb48 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1295,30 +1295,39 @@ static void fixup_discard_support(struct drbd_device *device, struct request_que
 	}
 }
 
+/* This is the workaround for "bio would need to, but cannot, be split" */
+static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
+{
+	unsigned int max_segments;
+
+	rcu_read_lock();
+	max_segments = rcu_dereference(device->ldev->disk_conf)->max_bio_bvecs;
+	rcu_read_unlock();
+
+	if (!max_segments)
+		return BLK_MAX_SEGMENTS;
+	return max_segments;
+}
+
 static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
 				   unsigned int max_bio_size, struct o_qlim *o)
 {
 	struct request_queue * const q = device->rq_queue;
 	unsigned int max_hw_sectors = max_bio_size >> 9;
-	unsigned int max_segments = 0;
+	unsigned int max_segments = BLK_MAX_SEGMENTS;
 	struct request_queue *b = NULL;
-	struct disk_conf *dc;
 
 	if (bdev) {
 		b = bdev->backing_bdev->bd_disk->queue;
 
 		max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
-		rcu_read_lock();
-		dc = rcu_dereference(device->ldev->disk_conf);
-		max_segments = dc->max_bio_bvecs;
-		rcu_read_unlock();
+		max_segments = drbd_backing_dev_max_segments(device);
 
 		blk_set_stacking_limits(&q->limits);
 	}
 
 	blk_queue_max_hw_sectors(q, max_hw_sectors);
-	/* This is the workaround for "bio would need to, but cannot, be split" */
-	blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
+	blk_queue_max_segments(q, max_segments);
 	blk_queue_segment_boundary(q, PAGE_SIZE-1);
 	decide_on_discard_support(device, bdev);
 
-- 
2.39.2

[PATCH 4/7] drbd: merge drbd_setup_queue_param into drbd_reconsider_queue_parameters

[Christoph Hellwig]

drbd_setup_queue_param is only called by drbd_reconsider_queue_parameters
and there is no really clear boundary of responsibilities between the
two.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 56 ++++++++++++++----------------------
 1 file changed, 22 insertions(+), 34 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0326b7322ceb48..0f40fdee089971 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1309,45 +1309,16 @@ static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 	return max_segments;
 }
 
-static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
-				   unsigned int max_bio_size, struct o_qlim *o)
-{
-	struct request_queue * const q = device->rq_queue;
-	unsigned int max_hw_sectors = max_bio_size >> 9;
-	unsigned int max_segments = BLK_MAX_SEGMENTS;
-	struct request_queue *b = NULL;
-
-	if (bdev) {
-		b = bdev->backing_bdev->bd_disk->queue;
-
-		max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
-		max_segments = drbd_backing_dev_max_segments(device);
-
-		blk_set_stacking_limits(&q->limits);
-	}
-
-	blk_queue_max_hw_sectors(q, max_hw_sectors);
-	blk_queue_max_segments(q, max_segments);
-	blk_queue_segment_boundary(q, PAGE_SIZE-1);
-	decide_on_discard_support(device, bdev);
-
-	if (b) {
-		blk_stack_limits(&q->limits, &b->limits, 0);
-		disk_update_readahead(device->vdisk);
-	}
-	fixup_write_zeroes(device, q);
-	fixup_discard_support(device, q);
-}
-
 void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
-	unsigned int now = queue_max_hw_sectors(device->rq_queue) <<
-			SECTOR_SHIFT;
+	struct request_queue * const q = device->rq_queue;
+	unsigned int now = queue_max_hw_sectors(q) << 9;
+	struct request_queue *b = NULL;
 	unsigned int new;
 
 	if (bdev) {
-		struct request_queue *b = bdev->backing_bdev->bd_disk->queue;
+		b = bdev->backing_bdev->bd_disk->queue;
 
 		device->local_max_bio_size =
 			queue_max_hw_sectors(b) << SECTOR_SHIFT;
@@ -1369,7 +1340,24 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		drbd_info(device, "max BIO size = %u\n", new);
 	}
 
-	drbd_setup_queue_param(device, bdev, new, o);
+	if (bdev) {
+		blk_set_stacking_limits(&q->limits);
+		blk_queue_max_segments(q,
+			drbd_backing_dev_max_segments(device));
+	} else {
+		blk_queue_max_segments(q, BLK_MAX_SEGMENTS);
+	}
+
+	blk_queue_max_hw_sectors(q, new >> SECTOR_SHIFT);
+	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
+	decide_on_discard_support(device, bdev);
+
+	if (bdev) {
+		blk_stack_limits(&q->limits, &b->limits, 0);
+		disk_update_readahead(device->vdisk);
+	}
+	fixup_write_zeroes(device, q);
+	fixup_discard_support(device, q);
 }
 
 /* Starts the worker thread */
-- 
2.39.2

[PATCH 5/7] drbd: don't set max_write_zeroes_sectors in decide_on_discard_support

[Christoph Hellwig]

fixup_write_zeroes always overrides the max_write_zeroes_sectors value
a little further down the callchain, so don't bother to setup a limit
in decide_on_discard_support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0f40fdee089971..a79b7fe5335de4 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1260,7 +1260,6 @@ static void decide_on_discard_support(struct drbd_device *device,
 	blk_queue_discard_granularity(q, 512);
 	max_discard_sectors = drbd_max_discard_sectors(connection);
 	blk_queue_max_discard_sectors(q, max_discard_sectors);
-	blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
 	return;
 
 not_supported:
-- 
2.39.2

[PATCH 6/7] drbd: split out a drbd_discard_supported helper

[Christoph Hellwig]

Add a helper to check if discard is supported for a given connection /
backing device combination.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index a79b7fe5335de4..94ed2b3ea6361d 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1231,24 +1231,33 @@ static unsigned int drbd_max_discard_sectors(struct drbd_connection *connection)
 	return AL_EXTENT_SIZE >> 9;
 }
 
-static void decide_on_discard_support(struct drbd_device *device,
+static bool drbd_discard_supported(struct drbd_connection *connection,
 		struct drbd_backing_dev *bdev)
 {
-	struct drbd_connection *connection =
-		first_peer_device(device)->connection;
-	struct request_queue *q = device->rq_queue;
-	unsigned int max_discard_sectors;
-
 	if (bdev && !bdev_max_discard_sectors(bdev->backing_bdev))
-		goto not_supported;
+		return false;
 
 	if (connection->cstate >= C_CONNECTED &&
 	    !(connection->agreed_features & DRBD_FF_TRIM)) {
 		drbd_info(connection,
 			"peer DRBD too old, does not support TRIM: disabling discards\n");
-		goto not_supported;
+		return false;
 	}
 
+	return true;
+}
+
+static void decide_on_discard_support(struct drbd_device *device,
+		struct drbd_backing_dev *bdev)
+{
+	struct drbd_connection *connection =
+		first_peer_device(device)->connection;
+	struct request_queue *q = device->rq_queue;
+	unsigned int max_discard_sectors;
+
+	if (!drbd_discard_supported(connection, bdev))
+		goto not_supported;
+
 	/*
 	 * We don't care for the granularity, really.
 	 *
-- 
2.39.2

[PATCH 7/7] drbd: atomically update queue limits in drbd_reconsider_queue_parameters

[Christoph Hellwig]

Switch drbd_reconsider_queue_parameters to set up the queue parameters
in an on-stack queue_limits structure and apply the atomically.  Remove
various helpers that have become so trivial that they can be folded into
drbd_reconsider_queue_parameters.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/drbd/drbd_nl.c | 119 ++++++++++++++---------------------
 1 file changed, 46 insertions(+), 73 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 94ed2b3ea6361d..fbd92803dc1da4 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1216,11 +1216,6 @@ static unsigned int drbd_max_peer_bio_size(struct drbd_device *device)
 	return DRBD_MAX_BIO_SIZE;
 }
 
-static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
-{
-	q->limits.discard_granularity = granularity;
-}
-
 static unsigned int drbd_max_discard_sectors(struct drbd_connection *connection)
 {
 	/* when we introduced REQ_WRITE_SAME support, we also bumped
@@ -1247,62 +1242,6 @@ static bool drbd_discard_supported(struct drbd_connection *connection,
 	return true;
 }
 
-static void decide_on_discard_support(struct drbd_device *device,
-		struct drbd_backing_dev *bdev)
-{
-	struct drbd_connection *connection =
-		first_peer_device(device)->connection;
-	struct request_queue *q = device->rq_queue;
-	unsigned int max_discard_sectors;
-
-	if (!drbd_discard_supported(connection, bdev))
-		goto not_supported;
-
-	/*
-	 * We don't care for the granularity, really.
-	 *
-	 * Stacking limits below should fix it for the local device.  Whether or
-	 * not it is a suitable granularity on the remote device is not our
-	 * problem, really. If you care, you need to use devices with similar
-	 * topology on all peers.
-	 */
-	blk_queue_discard_granularity(q, 512);
-	max_discard_sectors = drbd_max_discard_sectors(connection);
-	blk_queue_max_discard_sectors(q, max_discard_sectors);
-	return;
-
-not_supported:
-	blk_queue_discard_granularity(q, 0);
-	blk_queue_max_discard_sectors(q, 0);
-}
-
-static void fixup_write_zeroes(struct drbd_device *device, struct request_queue *q)
-{
-	/* Fixup max_write_zeroes_sectors after blk_stack_limits():
-	 * if we can handle "zeroes" efficiently on the protocol,
-	 * we want to do that, even if our backend does not announce
-	 * max_write_zeroes_sectors itself. */
-	struct drbd_connection *connection = first_peer_device(device)->connection;
-	/* If the peer announces WZEROES support, use it.  Otherwise, rather
-	 * send explicit zeroes than rely on some discard-zeroes-data magic. */
-	if (connection->agreed_features & DRBD_FF_WZEROES)
-		q->limits.max_write_zeroes_sectors = DRBD_MAX_BBIO_SECTORS;
-	else
-		q->limits.max_write_zeroes_sectors = 0;
-}
-
-static void fixup_discard_support(struct drbd_device *device, struct request_queue *q)
-{
-	unsigned int max_discard = device->rq_queue->limits.max_discard_sectors;
-	unsigned int discard_granularity =
-		device->rq_queue->limits.discard_granularity >> SECTOR_SHIFT;
-
-	if (discard_granularity > max_discard) {
-		blk_queue_discard_granularity(q, 0);
-		blk_queue_max_discard_sectors(q, 0);
-	}
-}
-
 /* This is the workaround for "bio would need to, but cannot, be split" */
 static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 {
@@ -1320,8 +1259,11 @@ static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
+	struct drbd_connection *connection =
+		first_peer_device(device)->connection;
 	struct request_queue * const q = device->rq_queue;
 	unsigned int now = queue_max_hw_sectors(q) << 9;
+	struct queue_limits lim;
 	struct request_queue *b = NULL;
 	unsigned int new;
 
@@ -1348,24 +1290,55 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		drbd_info(device, "max BIO size = %u\n", new);
 	}
 
+	lim = queue_limits_start_update(q);
 	if (bdev) {
-		blk_set_stacking_limits(&q->limits);
-		blk_queue_max_segments(q,
-			drbd_backing_dev_max_segments(device));
+		blk_set_stacking_limits(&lim);
+		lim.max_segments = drbd_backing_dev_max_segments(device);
 	} else {
-		blk_queue_max_segments(q, BLK_MAX_SEGMENTS);
+		lim.max_segments = BLK_MAX_SEGMENTS;
 	}
 
-	blk_queue_max_hw_sectors(q, new >> SECTOR_SHIFT);
-	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
-	decide_on_discard_support(device, bdev);
+	lim.max_hw_sectors = new >> SECTOR_SHIFT;
+	lim.seg_boundary_mask = PAGE_SIZE - 1;
 
-	if (bdev) {
-		blk_stack_limits(&q->limits, &b->limits, 0);
-		disk_update_readahead(device->vdisk);
+	/*
+	 * We don't care for the granularity, really.
+	 *
+	 * Stacking limits below should fix it for the local device.  Whether or
+	 * not it is a suitable granularity on the remote device is not our
+	 * problem, really. If you care, you need to use devices with similar
+	 * topology on all peers.
+	 */
+	if (drbd_discard_supported(connection, bdev)) {
+		lim.discard_granularity = 512;
+		lim.max_hw_discard_sectors =
+			drbd_max_discard_sectors(connection);
+	} else {
+		lim.discard_granularity = 0;
+		lim.max_hw_discard_sectors = 0;
 	}
-	fixup_write_zeroes(device, q);
-	fixup_discard_support(device, q);
+
+	if (bdev)
+		blk_stack_limits(&lim, &b->limits, 0);
+
+	/*
+	 * If we can handle "zeroes" efficiently on the protocol, we want to do
+	 * that, even if our backend does not announce max_write_zeroes_sectors
+	 * itself.
+	 */
+	if (connection->agreed_features & DRBD_FF_WZEROES)
+		lim.max_write_zeroes_sectors = DRBD_MAX_BBIO_SECTORS;
+	else
+		lim.max_write_zeroes_sectors = 0;
+
+	if ((lim.discard_granularity >> SECTOR_SHIFT) >
+	    lim.max_hw_discard_sectors) {
+		lim.discard_granularity = 0;
+		lim.max_hw_discard_sectors = 0;
+	}
+
+	if (queue_limits_commit_update(q, &lim))
+		drbd_err(device, "setting new queue limits failed\n");
 }
 
 /* Starts the worker thread */
-- 
2.39.2

[PATCH 0/7] drbd atomic queue limits conversion

[Philipp Reisner]

Hello Jens,

Here, with the Reviewed-by and Tested-by trailers.

Christoph Hellwig (7):
  drbd: pass the max_hw_sectors limit to blk_alloc_disk
  drbd: refactor drbd_reconsider_queue_parameters
  drbd: refactor the backing dev max_segments calculation
  drbd: merge drbd_setup_queue_param into
    drbd_reconsider_queue_parameters
  drbd: don't set max_write_zeroes_sectors in decide_on_discard_support
  drbd: split out a drbd_discard_supported helper
  drbd: atomically update queue limits in
    drbd_reconsider_queue_parameters

 drivers/block/drbd/drbd_main.c |  13 +-
 drivers/block/drbd/drbd_nl.c   | 210 ++++++++++++++++-----------------
 2 files changed, 110 insertions(+), 113 deletions(-)

-- 
2.40.1

Re: [PATCH 0/7] drbd atomic queue limits conversion

[Jens Axboe]

On Wed, 06 Mar 2024 15:03:25 +0100, Philipp Reisner wrote:
> Here, with the Reviewed-by and Tested-by trailers.
> 
> Christoph Hellwig (7):
>   drbd: pass the max_hw_sectors limit to blk_alloc_disk
>   drbd: refactor drbd_reconsider_queue_parameters
>   drbd: refactor the backing dev max_segments calculation
>   drbd: merge drbd_setup_queue_param into
>     drbd_reconsider_queue_parameters
>   drbd: don't set max_write_zeroes_sectors in decide_on_discard_support
>   drbd: split out a drbd_discard_supported helper
>   drbd: atomically update queue limits in
>     drbd_reconsider_queue_parameters
> 
> [...]

Applied, thanks!

[1/7] drbd: pass the max_hw_sectors limit to blk_alloc_disk
      commit: aa067325c05dc3a3aac588f40cacf8418f916cee
[2/7] drbd: refactor drbd_reconsider_queue_parameters
      commit: 342d81fde24152adf9747e6e126c8c3179d1a54c
[3/7] drbd: refactor the backing dev max_segments calculation
      commit: 2828908d5cc8396e7c91d04d67e03ed834234bcd
[4/7] drbd: merge drbd_setup_queue_param into drbd_reconsider_queue_parameters
      commit: e16344e506314e35b1a5a8ccd7b88f4b1844ebb0
[5/7] drbd: don't set max_write_zeroes_sectors in decide_on_discard_support
      commit: e3992e02c970f6eb803b98b9f733cad40f190161
[6/7] drbd: split out a drbd_discard_supported helper
      commit: 5eaee6e9c8f9940ecee93678972774fb8dd450d5
[7/7] drbd: atomically update queue limits in drbd_reconsider_queue_parameters
      commit: e6dfe748f09e37f77437bd337f891f5b57d5d5a2

Best regards,
-- 
Jens Axboe

[PATCH 1/7] drbd: pass the max_hw_sectors limit to blk_alloc_disk

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

Pass a queue_limits structure with the max_hw_sectors limit to
blk_alloc_disk instead of updating the limit on the allocated gendisk.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_main.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index cea1e537fd56..113b441d4d36 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2690,6 +2690,14 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	int id;
 	int vnr = adm_ctx->volume;
 	enum drbd_ret_code err = ERR_NOMEM;
+	struct queue_limits lim = {
+		/*
+		 * Setting the max_hw_sectors to an odd value of 8kibyte here.
+		 * This triggers a max_bio_size message upon first attach or
+		 * connect.
+		 */
+		.max_hw_sectors		= DRBD_MAX_BIO_SIZE_SAFE >> 8,
+	};
 
 	device = minor_to_device(minor);
 	if (device)
@@ -2708,7 +2716,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 
 	drbd_init_set_defaults(device);
 
-	disk = blk_alloc_disk(NULL, NUMA_NO_NODE);
+	disk = blk_alloc_disk(&lim, NUMA_NO_NODE);
 	if (IS_ERR(disk)) {
 		err = PTR_ERR(disk);
 		goto out_no_disk;
@@ -2729,9 +2737,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 
 	blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, disk->queue);
 	blk_queue_write_cache(disk->queue, true, true);
-	/* Setting the max_hw_sectors to an odd value of 8kibyte here
-	   This triggers a max_bio_size message upon first attach or connect */
-	blk_queue_max_hw_sectors(disk->queue, DRBD_MAX_BIO_SIZE_SAFE >> 8);
 
 	device->md_io.page = alloc_page(GFP_KERNEL);
 	if (!device->md_io.page)
-- 
2.40.1

[PATCH 2/7] drbd: refactor drbd_reconsider_queue_parameters

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

Split out a drbd_max_peer_bio_size helper for the peer I/O size,
and condense the various checks to a nested min3(..., max())) instead
of using a lot of local variables.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 84 +++++++++++++++++++++---------------
 1 file changed, 49 insertions(+), 35 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 43747a1aae43..9135001a8e57 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1189,6 +1189,33 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
 	return 0;
 }
 
+static unsigned int drbd_max_peer_bio_size(struct drbd_device *device)
+{
+	/*
+	 * We may ignore peer limits if the peer is modern enough.  From 8.3.8
+	 * onwards the peer can use multiple BIOs for a single peer_request.
+	 */
+	if (device->state.conn < C_WF_REPORT_PARAMS)
+		return device->peer_max_bio_size;
+
+	if (first_peer_device(device)->connection->agreed_pro_version < 94)
+		return min(device->peer_max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
+
+	/*
+	 * Correct old drbd (up to 8.3.7) if it believes it can do more than
+	 * 32KiB.
+	 */
+	if (first_peer_device(device)->connection->agreed_pro_version == 94)
+		return DRBD_MAX_SIZE_H80_PACKET;
+
+	/*
+	 * drbd 8.3.8 onwards, before 8.4.0
+	 */
+	if (first_peer_device(device)->connection->agreed_pro_version < 100)
+		return DRBD_MAX_BIO_SIZE_P95;
+	return DRBD_MAX_BIO_SIZE;
+}
+
 static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
 {
 	q->limits.discard_granularity = granularity;
@@ -1303,48 +1330,35 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
 	fixup_discard_support(device, q);
 }
 
-void drbd_reconsider_queue_parameters(struct drbd_device *device, struct drbd_backing_dev *bdev, struct o_qlim *o)
+void drbd_reconsider_queue_parameters(struct drbd_device *device,
+		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
-	unsigned int now, new, local, peer;
-
-	now = queue_max_hw_sectors(device->rq_queue) << 9;
-	local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
-	peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */
+	unsigned int now = queue_max_hw_sectors(device->rq_queue) <<
+			SECTOR_SHIFT;
+	unsigned int new;
 
 	if (bdev) {
-		local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
-		device->local_max_bio_size = local;
-	}
-	local = min(local, DRBD_MAX_BIO_SIZE);
-
-	/* We may ignore peer limits if the peer is modern enough.
-	   Because new from 8.3.8 onwards the peer can use multiple
-	   BIOs for a single peer_request */
-	if (device->state.conn >= C_WF_REPORT_PARAMS) {
-		if (first_peer_device(device)->connection->agreed_pro_version < 94)
-			peer = min(device->peer_max_bio_size, DRBD_MAX_SIZE_H80_PACKET);
-			/* Correct old drbd (up to 8.3.7) if it believes it can do more than 32KiB */
-		else if (first_peer_device(device)->connection->agreed_pro_version == 94)
-			peer = DRBD_MAX_SIZE_H80_PACKET;
-		else if (first_peer_device(device)->connection->agreed_pro_version < 100)
-			peer = DRBD_MAX_BIO_SIZE_P95;  /* drbd 8.3.8 onwards, before 8.4.0 */
-		else
-			peer = DRBD_MAX_BIO_SIZE;
+		struct request_queue *b = bdev->backing_bdev->bd_disk->queue;
 
-		/* We may later detach and re-attach on a disconnected Primary.
-		 * Avoid this setting to jump back in that case.
-		 * We want to store what we know the peer DRBD can handle,
-		 * not what the peer IO backend can handle. */
-		if (peer > device->peer_max_bio_size)
-			device->peer_max_bio_size = peer;
+		device->local_max_bio_size =
+			queue_max_hw_sectors(b) << SECTOR_SHIFT;
 	}
-	new = min(local, peer);
 
-	if (device->state.role == R_PRIMARY && new < now)
-		drbd_err(device, "ASSERT FAILED new < now; (%u < %u)\n", new, now);
-
-	if (new != now)
+	/*
+	 * We may later detach and re-attach on a disconnected Primary.  Avoid
+	 * decreasing the value in this case.
+	 *
+	 * We want to store what we know the peer DRBD can handle, not what the
+	 * peer IO backend can handle.
+	 */
+	new = min3(DRBD_MAX_BIO_SIZE, device->local_max_bio_size,
+		max(drbd_max_peer_bio_size(device), device->peer_max_bio_size));
+	if (new != now) {
+		if (device->state.role == R_PRIMARY && new < now)
+			drbd_err(device, "ASSERT FAILED new < now; (%u < %u)\n",
+					new, now);
 		drbd_info(device, "max BIO size = %u\n", new);
+	}
 
 	drbd_setup_queue_param(device, bdev, new, o);
 }
-- 
2.40.1

[PATCH 3/7] drbd: refactor the backing dev max_segments calculation

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

Factor out a drbd_backing_dev_max_segments helper that checks the
backing device limitation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 9135001a8e57..0326b7322ceb 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1295,30 +1295,39 @@ static void fixup_discard_support(struct drbd_device *device, struct request_que
 	}
 }
 
+/* This is the workaround for "bio would need to, but cannot, be split" */
+static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
+{
+	unsigned int max_segments;
+
+	rcu_read_lock();
+	max_segments = rcu_dereference(device->ldev->disk_conf)->max_bio_bvecs;
+	rcu_read_unlock();
+
+	if (!max_segments)
+		return BLK_MAX_SEGMENTS;
+	return max_segments;
+}
+
 static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
 				   unsigned int max_bio_size, struct o_qlim *o)
 {
 	struct request_queue * const q = device->rq_queue;
 	unsigned int max_hw_sectors = max_bio_size >> 9;
-	unsigned int max_segments = 0;
+	unsigned int max_segments = BLK_MAX_SEGMENTS;
 	struct request_queue *b = NULL;
-	struct disk_conf *dc;
 
 	if (bdev) {
 		b = bdev->backing_bdev->bd_disk->queue;
 
 		max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
-		rcu_read_lock();
-		dc = rcu_dereference(device->ldev->disk_conf);
-		max_segments = dc->max_bio_bvecs;
-		rcu_read_unlock();
+		max_segments = drbd_backing_dev_max_segments(device);
 
 		blk_set_stacking_limits(&q->limits);
 	}
 
 	blk_queue_max_hw_sectors(q, max_hw_sectors);
-	/* This is the workaround for "bio would need to, but cannot, be split" */
-	blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
+	blk_queue_max_segments(q, max_segments);
 	blk_queue_segment_boundary(q, PAGE_SIZE-1);
 	decide_on_discard_support(device, bdev);
 
-- 
2.40.1

[PATCH 4/7] drbd: merge drbd_setup_queue_param into drbd_reconsider_queue_parameters

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

drbd_setup_queue_param is only called by drbd_reconsider_queue_parameters
and there is no really clear boundary of responsibilities between the
two.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 56 ++++++++++++++----------------------
 1 file changed, 22 insertions(+), 34 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0326b7322ceb..0f40fdee0899 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1309,45 +1309,16 @@ static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 	return max_segments;
 }
 
-static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
-				   unsigned int max_bio_size, struct o_qlim *o)
-{
-	struct request_queue * const q = device->rq_queue;
-	unsigned int max_hw_sectors = max_bio_size >> 9;
-	unsigned int max_segments = BLK_MAX_SEGMENTS;
-	struct request_queue *b = NULL;
-
-	if (bdev) {
-		b = bdev->backing_bdev->bd_disk->queue;
-
-		max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
-		max_segments = drbd_backing_dev_max_segments(device);
-
-		blk_set_stacking_limits(&q->limits);
-	}
-
-	blk_queue_max_hw_sectors(q, max_hw_sectors);
-	blk_queue_max_segments(q, max_segments);
-	blk_queue_segment_boundary(q, PAGE_SIZE-1);
-	decide_on_discard_support(device, bdev);
-
-	if (b) {
-		blk_stack_limits(&q->limits, &b->limits, 0);
-		disk_update_readahead(device->vdisk);
-	}
-	fixup_write_zeroes(device, q);
-	fixup_discard_support(device, q);
-}
-
 void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
-	unsigned int now = queue_max_hw_sectors(device->rq_queue) <<
-			SECTOR_SHIFT;
+	struct request_queue * const q = device->rq_queue;
+	unsigned int now = queue_max_hw_sectors(q) << 9;
+	struct request_queue *b = NULL;
 	unsigned int new;
 
 	if (bdev) {
-		struct request_queue *b = bdev->backing_bdev->bd_disk->queue;
+		b = bdev->backing_bdev->bd_disk->queue;
 
 		device->local_max_bio_size =
 			queue_max_hw_sectors(b) << SECTOR_SHIFT;
@@ -1369,7 +1340,24 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		drbd_info(device, "max BIO size = %u\n", new);
 	}
 
-	drbd_setup_queue_param(device, bdev, new, o);
+	if (bdev) {
+		blk_set_stacking_limits(&q->limits);
+		blk_queue_max_segments(q,
+			drbd_backing_dev_max_segments(device));
+	} else {
+		blk_queue_max_segments(q, BLK_MAX_SEGMENTS);
+	}
+
+	blk_queue_max_hw_sectors(q, new >> SECTOR_SHIFT);
+	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
+	decide_on_discard_support(device, bdev);
+
+	if (bdev) {
+		blk_stack_limits(&q->limits, &b->limits, 0);
+		disk_update_readahead(device->vdisk);
+	}
+	fixup_write_zeroes(device, q);
+	fixup_discard_support(device, q);
 }
 
 /* Starts the worker thread */
-- 
2.40.1

[PATCH 5/7] drbd: don't set max_write_zeroes_sectors in decide_on_discard_support

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

fixup_write_zeroes always overrides the max_write_zeroes_sectors value
a little further down the callchain, so don't bother to setup a limit
in decide_on_discard_support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0f40fdee0899..a79b7fe5335d 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1260,7 +1260,6 @@ static void decide_on_discard_support(struct drbd_device *device,
 	blk_queue_discard_granularity(q, 512);
 	max_discard_sectors = drbd_max_discard_sectors(connection);
 	blk_queue_max_discard_sectors(q, max_discard_sectors);
-	blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
 	return;
 
 not_supported:
-- 
2.40.1

[PATCH 6/7] drbd: split out a drbd_discard_supported helper

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

Add a helper to check if discard is supported for a given connection /
backing device combination.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index a79b7fe5335d..94ed2b3ea636 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1231,24 +1231,33 @@ static unsigned int drbd_max_discard_sectors(struct drbd_connection *connection)
 	return AL_EXTENT_SIZE >> 9;
 }
 
-static void decide_on_discard_support(struct drbd_device *device,
+static bool drbd_discard_supported(struct drbd_connection *connection,
 		struct drbd_backing_dev *bdev)
 {
-	struct drbd_connection *connection =
-		first_peer_device(device)->connection;
-	struct request_queue *q = device->rq_queue;
-	unsigned int max_discard_sectors;
-
 	if (bdev && !bdev_max_discard_sectors(bdev->backing_bdev))
-		goto not_supported;
+		return false;
 
 	if (connection->cstate >= C_CONNECTED &&
 	    !(connection->agreed_features & DRBD_FF_TRIM)) {
 		drbd_info(connection,
 			"peer DRBD too old, does not support TRIM: disabling discards\n");
-		goto not_supported;
+		return false;
 	}
 
+	return true;
+}
+
+static void decide_on_discard_support(struct drbd_device *device,
+		struct drbd_backing_dev *bdev)
+{
+	struct drbd_connection *connection =
+		first_peer_device(device)->connection;
+	struct request_queue *q = device->rq_queue;
+	unsigned int max_discard_sectors;
+
+	if (!drbd_discard_supported(connection, bdev))
+		goto not_supported;
+
 	/*
 	 * We don't care for the granularity, really.
 	 *
-- 
2.40.1

[PATCH 7/7] drbd: atomically update queue limits in drbd_reconsider_queue_parameters

[Philipp Reisner]

From: Christoph Hellwig <hch@lst.de>

Switch drbd_reconsider_queue_parameters to set up the queue parameters
in an on-stack queue_limits structure and apply the atomically.  Remove
various helpers that have become so trivial that they can be folded into
drbd_reconsider_queue_parameters.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 119 ++++++++++++++---------------------
 1 file changed, 46 insertions(+), 73 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 94ed2b3ea636..fbd92803dc1d 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1216,11 +1216,6 @@ static unsigned int drbd_max_peer_bio_size(struct drbd_device *device)
 	return DRBD_MAX_BIO_SIZE;
 }
 
-static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
-{
-	q->limits.discard_granularity = granularity;
-}
-
 static unsigned int drbd_max_discard_sectors(struct drbd_connection *connection)
 {
 	/* when we introduced REQ_WRITE_SAME support, we also bumped
@@ -1247,62 +1242,6 @@ static bool drbd_discard_supported(struct drbd_connection *connection,
 	return true;
 }
 
-static void decide_on_discard_support(struct drbd_device *device,
-		struct drbd_backing_dev *bdev)
-{
-	struct drbd_connection *connection =
-		first_peer_device(device)->connection;
-	struct request_queue *q = device->rq_queue;
-	unsigned int max_discard_sectors;
-
-	if (!drbd_discard_supported(connection, bdev))
-		goto not_supported;
-
-	/*
-	 * We don't care for the granularity, really.
-	 *
-	 * Stacking limits below should fix it for the local device.  Whether or
-	 * not it is a suitable granularity on the remote device is not our
-	 * problem, really. If you care, you need to use devices with similar
-	 * topology on all peers.
-	 */
-	blk_queue_discard_granularity(q, 512);
-	max_discard_sectors = drbd_max_discard_sectors(connection);
-	blk_queue_max_discard_sectors(q, max_discard_sectors);
-	return;
-
-not_supported:
-	blk_queue_discard_granularity(q, 0);
-	blk_queue_max_discard_sectors(q, 0);
-}
-
-static void fixup_write_zeroes(struct drbd_device *device, struct request_queue *q)
-{
-	/* Fixup max_write_zeroes_sectors after blk_stack_limits():
-	 * if we can handle "zeroes" efficiently on the protocol,
-	 * we want to do that, even if our backend does not announce
-	 * max_write_zeroes_sectors itself. */
-	struct drbd_connection *connection = first_peer_device(device)->connection;
-	/* If the peer announces WZEROES support, use it.  Otherwise, rather
-	 * send explicit zeroes than rely on some discard-zeroes-data magic. */
-	if (connection->agreed_features & DRBD_FF_WZEROES)
-		q->limits.max_write_zeroes_sectors = DRBD_MAX_BBIO_SECTORS;
-	else
-		q->limits.max_write_zeroes_sectors = 0;
-}
-
-static void fixup_discard_support(struct drbd_device *device, struct request_queue *q)
-{
-	unsigned int max_discard = device->rq_queue->limits.max_discard_sectors;
-	unsigned int discard_granularity =
-		device->rq_queue->limits.discard_granularity >> SECTOR_SHIFT;
-
-	if (discard_granularity > max_discard) {
-		blk_queue_discard_granularity(q, 0);
-		blk_queue_max_discard_sectors(q, 0);
-	}
-}
-
 /* This is the workaround for "bio would need to, but cannot, be split" */
 static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 {
@@ -1320,8 +1259,11 @@ static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
 void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		struct drbd_backing_dev *bdev, struct o_qlim *o)
 {
+	struct drbd_connection *connection =
+		first_peer_device(device)->connection;
 	struct request_queue * const q = device->rq_queue;
 	unsigned int now = queue_max_hw_sectors(q) << 9;
+	struct queue_limits lim;
 	struct request_queue *b = NULL;
 	unsigned int new;
 
@@ -1348,24 +1290,55 @@ void drbd_reconsider_queue_parameters(struct drbd_device *device,
 		drbd_info(device, "max BIO size = %u\n", new);
 	}
 
+	lim = queue_limits_start_update(q);
 	if (bdev) {
-		blk_set_stacking_limits(&q->limits);
-		blk_queue_max_segments(q,
-			drbd_backing_dev_max_segments(device));
+		blk_set_stacking_limits(&lim);
+		lim.max_segments = drbd_backing_dev_max_segments(device);
 	} else {
-		blk_queue_max_segments(q, BLK_MAX_SEGMENTS);
+		lim.max_segments = BLK_MAX_SEGMENTS;
 	}
 
-	blk_queue_max_hw_sectors(q, new >> SECTOR_SHIFT);
-	blk_queue_segment_boundary(q, PAGE_SIZE - 1);
-	decide_on_discard_support(device, bdev);
+	lim.max_hw_sectors = new >> SECTOR_SHIFT;
+	lim.seg_boundary_mask = PAGE_SIZE - 1;
 
-	if (bdev) {
-		blk_stack_limits(&q->limits, &b->limits, 0);
-		disk_update_readahead(device->vdisk);
+	/*
+	 * We don't care for the granularity, really.
+	 *
+	 * Stacking limits below should fix it for the local device.  Whether or
+	 * not it is a suitable granularity on the remote device is not our
+	 * problem, really. If you care, you need to use devices with similar
+	 * topology on all peers.
+	 */
+	if (drbd_discard_supported(connection, bdev)) {
+		lim.discard_granularity = 512;
+		lim.max_hw_discard_sectors =
+			drbd_max_discard_sectors(connection);
+	} else {
+		lim.discard_granularity = 0;
+		lim.max_hw_discard_sectors = 0;
 	}
-	fixup_write_zeroes(device, q);
-	fixup_discard_support(device, q);
+
+	if (bdev)
+		blk_stack_limits(&lim, &b->limits, 0);
+
+	/*
+	 * If we can handle "zeroes" efficiently on the protocol, we want to do
+	 * that, even if our backend does not announce max_write_zeroes_sectors
+	 * itself.
+	 */
+	if (connection->agreed_features & DRBD_FF_WZEROES)
+		lim.max_write_zeroes_sectors = DRBD_MAX_BBIO_SECTORS;
+	else
+		lim.max_write_zeroes_sectors = 0;
+
+	if ((lim.discard_granularity >> SECTOR_SHIFT) >
+	    lim.max_hw_discard_sectors) {
+		lim.discard_granularity = 0;
+		lim.max_hw_discard_sectors = 0;
+	}
+
+	if (queue_limits_commit_update(q, &lim))
+		drbd_err(device, "setting new queue limits failed\n");
 }
 
 /* Starts the worker thread */
-- 
2.40.1