convert xen-blkfront to atomic queue limit updates

convert xen-blkfront to atomic queue limit updates

[Christoph Hellwig]

Hi all,

this series converts xen-blkfront to the new atomic queue limits update
API in the block tree.  I don't have a Xen setup so this is compile
tested only.

Diffstat:
 xen-blkfront.c |   53 +++++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

[PATCH 1/4] xen-blkfront: set max_discard/secure erase limits to UINT_MAX

[Christoph Hellwig]

Currently xen-blkfront set the max discard limit to the capacity of
the device, which is suboptimal when the capacity changes.  Just set
it to UINT_MAX, which has the same effect except and is simpler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/xen-blkfront.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 4cc2884e748463..f78167cd5a6333 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -944,20 +944,18 @@ static const struct blk_mq_ops blkfront_mq_ops = {
 static void blkif_set_queue_limits(struct blkfront_info *info)
 {
 	struct request_queue *rq = info->rq;
-	struct gendisk *gd = info->gd;
 	unsigned int segments = info->max_indirect_segments ? :
 				BLKIF_MAX_SEGMENTS_PER_REQUEST;
 
 	blk_queue_flag_set(QUEUE_FLAG_VIRT, rq);
 
 	if (info->feature_discard) {
-		blk_queue_max_discard_sectors(rq, get_capacity(gd));
+		blk_queue_max_discard_sectors(rq, UINT_MAX);
 		rq->limits.discard_granularity = info->discard_granularity ?:
 						 info->physical_sector_size;
 		rq->limits.discard_alignment = info->discard_alignment;
 		if (info->feature_secdiscard)
-			blk_queue_max_secure_erase_sectors(rq,
-							   get_capacity(gd));
+			blk_queue_max_secure_erase_sectors(rq, UINT_MAX);
 	}
 
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
-- 
2.39.2

Re: [PATCH 1/4] xen-blkfront: set max_discard/secure erase limits to UINT_MAX

[Roger Pau Monné]

On Tue, Feb 20, 2024 at 09:49:32AM +0100, Christoph Hellwig wrote:
> Currently xen-blkfront set the max discard limit to the capacity of
> the device, which is suboptimal when the capacity changes.  Just set
> it to UINT_MAX, which has the same effect except and is simpler.

Extra 'except' in the line above?

> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

Re: [PATCH 1/4] xen-blkfront: set max_discard/secure erase limits to UINT_MAX

[Christoph Hellwig]

On Tue, Feb 20, 2024 at 12:39:59PM +0100, Roger Pau Monné wrote:
> On Tue, Feb 20, 2024 at 09:49:32AM +0100, Christoph Hellwig wrote:
> > Currently xen-blkfront set the max discard limit to the capacity of
> > the device, which is suboptimal when the capacity changes.  Just set
> > it to UINT_MAX, which has the same effect except and is simpler.
> 
> Extra 'except' in the line above?

Yes, thanks.

[PATCH 2/4] xen-blkfront: rely on the default discard granularity

[Christoph Hellwig]

The block layer now sets the discard granularity to the physical
block size default.  Take advantage of that in xen-blkfront and only
set the discard granularity if explicitly specified.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/xen-blkfront.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index f78167cd5a6333..1258f24b285500 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -951,8 +951,8 @@ static void blkif_set_queue_limits(struct blkfront_info *info)
 
 	if (info->feature_discard) {
 		blk_queue_max_discard_sectors(rq, UINT_MAX);
-		rq->limits.discard_granularity = info->discard_granularity ?:
-						 info->physical_sector_size;
+		if (info->discard_granularity)
+			rq->limits.discard_granularity = info->discard_granularity;
 		rq->limits.discard_alignment = info->discard_alignment;
 		if (info->feature_secdiscard)
 			blk_queue_max_secure_erase_sectors(rq, UINT_MAX);
-- 
2.39.2

Re: [PATCH 2/4] xen-blkfront: rely on the default discard granularity

[Roger Pau Monné]

On Tue, Feb 20, 2024 at 09:49:33AM +0100, Christoph Hellwig wrote:
> The block layer now sets the discard granularity to the physical
> block size default.  Take advantage of that in xen-blkfront and only
> set the discard granularity if explicitly specified.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Roger Pau Monné <roger.apu@citrix.com>

Thanks, Roger.

[PATCH 3/4] xen-blkfront: don't redundantly set max_sements in blkif_recover

[Christoph Hellwig]

blkif_set_queue_limits already sets the max_sements limits, so don't do
it a second time.  Also remove a comment about a long fixe bug in
blk_mq_update_nr_hw_queues.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/xen-blkfront.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 1258f24b285500..7664638a0abbfa 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -2008,14 +2008,10 @@ static int blkif_recover(struct blkfront_info *info)
 	struct request *req, *n;
 	int rc;
 	struct bio *bio;
-	unsigned int segs;
 	struct blkfront_ring_info *rinfo;
 
 	blkfront_gather_backend_features(info);
-	/* Reset limits changed by blk_mq_update_nr_hw_queues(). */
 	blkif_set_queue_limits(info);
-	segs = info->max_indirect_segments ? : BLKIF_MAX_SEGMENTS_PER_REQUEST;
-	blk_queue_max_segments(info->rq, segs / GRANTS_PER_PSEG);
 
 	for_each_rinfo(info, rinfo, r_index) {
 		rc = blkfront_setup_indirect(rinfo);
@@ -2035,7 +2031,9 @@ static int blkif_recover(struct blkfront_info *info)
 	list_for_each_entry_safe(req, n, &info->requests, queuelist) {
 		/* Requeue pending requests (flush or discard) */
 		list_del_init(&req->queuelist);
-		BUG_ON(req->nr_phys_segments > segs);
+		BUG_ON(req->nr_phys_segments >
+		       (info->max_indirect_segments ? :
+			BLKIF_MAX_SEGMENTS_PER_REQUEST));
 		blk_mq_requeue_request(req, false);
 	}
 	blk_mq_start_stopped_hw_queues(info->rq, true);
-- 
2.39.2

Re: [PATCH 3/4] xen-blkfront: don't redundantly set max_sements in blkif_recover

[Roger Pau Monné]

On Tue, Feb 20, 2024 at 09:49:34AM +0100, Christoph Hellwig wrote:
> blkif_set_queue_limits already sets the max_sements limits, so don't do
> it a second time.  Also remove a comment about a long fixe bug in
> blk_mq_update_nr_hw_queues.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

[PATCH 4/4] xen-blkfront: atomically update queue limits

[Christoph Hellwig]

Pass the initial queue limits to blk_mq_alloc_disk and use the
blkif_set_queue_limits API to update the limits on reconnect.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/xen-blkfront.c | 41 ++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7664638a0abbfa..b77707ca2c5aa6 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -941,37 +941,35 @@ static const struct blk_mq_ops blkfront_mq_ops = {
 	.complete = blkif_complete_rq,
 };
 
-static void blkif_set_queue_limits(struct blkfront_info *info)
+static void blkif_set_queue_limits(struct blkfront_info *info,
+		struct queue_limits *lim)
 {
-	struct request_queue *rq = info->rq;
 	unsigned int segments = info->max_indirect_segments ? :
 				BLKIF_MAX_SEGMENTS_PER_REQUEST;
 
-	blk_queue_flag_set(QUEUE_FLAG_VIRT, rq);
-
 	if (info->feature_discard) {
-		blk_queue_max_discard_sectors(rq, UINT_MAX);
+		lim->max_hw_discard_sectors = UINT_MAX;
 		if (info->discard_granularity)
-			rq->limits.discard_granularity = info->discard_granularity;
-		rq->limits.discard_alignment = info->discard_alignment;
+			lim->discard_granularity = info->discard_granularity;
+		lim->discard_alignment = info->discard_alignment;
 		if (info->feature_secdiscard)
-			blk_queue_max_secure_erase_sectors(rq, UINT_MAX);
+			lim->max_secure_erase_sectors = UINT_MAX;
 	}
 
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
-	blk_queue_logical_block_size(rq, info->sector_size);
-	blk_queue_physical_block_size(rq, info->physical_sector_size);
-	blk_queue_max_hw_sectors(rq, (segments * XEN_PAGE_SIZE) / 512);
+	lim->logical_block_size = info->sector_size;
+	lim->physical_block_size = info->physical_sector_size;
+	lim->max_hw_sectors = (segments * XEN_PAGE_SIZE) / 512;
 
 	/* Each segment in a request is up to an aligned page in size. */
-	blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
-	blk_queue_max_segment_size(rq, PAGE_SIZE);
+	lim->seg_boundary_mask = PAGE_SIZE - 1;
+	lim->max_segment_size = PAGE_SIZE;
 
 	/* Ensure a merged request will fit in a single I/O ring slot. */
-	blk_queue_max_segments(rq, segments / GRANTS_PER_PSEG);
+	lim->max_segments = segments / GRANTS_PER_PSEG;
 
 	/* Make sure buffer addresses are sector-aligned. */
-	blk_queue_dma_alignment(rq, 511);
+	lim->dma_alignment = 511;
 }
 
 static const char *flush_info(struct blkfront_info *info)
@@ -1068,6 +1066,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 		struct blkfront_info *info, u16 sector_size,
 		unsigned int physical_sector_size)
 {
+	struct queue_limits lim = {};
 	struct gendisk *gd;
 	int nr_minors = 1;
 	int err;
@@ -1134,11 +1133,13 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 	if (err)
 		goto out_release_minors;
 
-	gd = blk_mq_alloc_disk(&info->tag_set, NULL, info);
+	blkif_set_queue_limits(info, &lim);
+	gd = blk_mq_alloc_disk(&info->tag_set, &lim, info);
 	if (IS_ERR(gd)) {
 		err = PTR_ERR(gd);
 		goto out_free_tag_set;
 	}
+	blk_queue_flag_set(QUEUE_FLAG_VIRT, gd->queue);
 
 	strcpy(gd->disk_name, DEV_NAME);
 	ptr = encode_disk_name(gd->disk_name + sizeof(DEV_NAME) - 1, offset);
@@ -1160,7 +1161,6 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 	info->gd = gd;
 	info->sector_size = sector_size;
 	info->physical_sector_size = physical_sector_size;
-	blkif_set_queue_limits(info);
 
 	xlvbd_flush(info);
 
@@ -2004,14 +2004,19 @@ static int blkfront_probe(struct xenbus_device *dev,
 
 static int blkif_recover(struct blkfront_info *info)
 {
+	struct queue_limits lim;
 	unsigned int r_index;
 	struct request *req, *n;
 	int rc;
 	struct bio *bio;
 	struct blkfront_ring_info *rinfo;
 
+	lim = queue_limits_start_update(info->rq);
 	blkfront_gather_backend_features(info);
-	blkif_set_queue_limits(info);
+	blkif_set_queue_limits(info, &lim);
+	rc = queue_limits_commit_update(info->rq, &lim);
+	if (rc)
+		return rc;
 
 	for_each_rinfo(info, rinfo, r_index) {
 		rc = blkfront_setup_indirect(rinfo);
-- 
2.39.2

Re: [PATCH 4/4] xen-blkfront: atomically update queue limits

[Roger Pau Monné]

On Tue, Feb 20, 2024 at 09:49:35AM +0100, Christoph Hellwig wrote:
> Pass the initial queue limits to blk_mq_alloc_disk and use the
> blkif_set_queue_limits API to update the limits on reconnect.

Allocating queue_limits on the stack might be a bit risky, as I fear
this struct is likely to grow?

> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Just one addition while you are already modifying a line.

> ---
>  drivers/block/xen-blkfront.c | 41 ++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 7664638a0abbfa..b77707ca2c5aa6 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -941,37 +941,35 @@ static const struct blk_mq_ops blkfront_mq_ops = {
>  	.complete = blkif_complete_rq,
>  };
>  
> -static void blkif_set_queue_limits(struct blkfront_info *info)
> +static void blkif_set_queue_limits(struct blkfront_info *info,

While there, could you also constify info?

Thanks, Roger.

Re: [PATCH 4/4] xen-blkfront: atomically update queue limits

[Christoph Hellwig]

On Tue, Feb 20, 2024 at 01:35:07PM +0100, Roger Pau Monné wrote:
> On Tue, Feb 20, 2024 at 09:49:35AM +0100, Christoph Hellwig wrote:
> > Pass the initial queue limits to blk_mq_alloc_disk and use the
> > blkif_set_queue_limits API to update the limits on reconnect.
> 
> Allocating queue_limits on the stack might be a bit risky, as I fear
> this struct is likely to grow?

It might grow a little bit, but it's not actually that large, epecially
in a simple probe context that isn't in memory reclaim or similar.

> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Acked-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Just one addition while you are already modifying a line.
> 
> > ---
> >  drivers/block/xen-blkfront.c | 41 ++++++++++++++++++++----------------
> >  1 file changed, 23 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> > index 7664638a0abbfa..b77707ca2c5aa6 100644
> > --- a/drivers/block/xen-blkfront.c
> > +++ b/drivers/block/xen-blkfront.c
> > @@ -941,37 +941,35 @@ static const struct blk_mq_ops blkfront_mq_ops = {
> >  	.complete = blkif_complete_rq,
> >  };
> >  
> > -static void blkif_set_queue_limits(struct blkfront_info *info)
> > +static void blkif_set_queue_limits(struct blkfront_info *info,
> 
> While there, could you also constify info?

Sure.

convert xen-blkfront to atomic queue limit updates v2

[Christoph Hellwig]

Hi all,

this series converts xen-blkfront to the new atomic queue limits update
API in the block tree.  I don't have a Xen setup so this is compile
tested only.

Changes since v1:
 - constify the info argument to blkif_set_queue_limits
 - remove a spurious word from a commit message

Diffstat:
 xen-blkfront.c |   53 +++++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

[PATCH 2/4] xen-blkfront: rely on the default discard granularity

[Christoph Hellwig]

The block layer now sets the discard granularity to the physical
block size default.  Take advantage of that in xen-blkfront and only
set the discard granularity if explicitly specified.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
---
 drivers/block/xen-blkfront.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index f78167cd5a6333..1258f24b285500 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -951,8 +951,8 @@ static void blkif_set_queue_limits(struct blkfront_info *info)
 
 	if (info->feature_discard) {
 		blk_queue_max_discard_sectors(rq, UINT_MAX);
-		rq->limits.discard_granularity = info->discard_granularity ?:
-						 info->physical_sector_size;
+		if (info->discard_granularity)
+			rq->limits.discard_granularity = info->discard_granularity;
 		rq->limits.discard_alignment = info->discard_alignment;
 		if (info->feature_secdiscard)
 			blk_queue_max_secure_erase_sectors(rq, UINT_MAX);
-- 
2.39.2