Message ID | 20230612203314.17820-9-bvanassche@acm.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | Support limits below the page size | expand |
On 6/13/23 05:33, Bart Van Assche wrote: > Add support for configuring the maximum segment size. > > Add support for segments smaller than the page size. > > This patch enables testing segments smaller than the page size with a > driver that does not call blk_rq_map_sg(). > > Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> > Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Ming Lei <ming.lei@redhat.com> > Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com> > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > --- > drivers/block/null_blk/main.c | 19 ++++++++++++++++--- > drivers/block/null_blk/null_blk.h | 1 + > 2 files changed, 17 insertions(+), 3 deletions(-) > > diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c > index b3fedafe301e..9c9098f1bd52 100644 > --- a/drivers/block/null_blk/main.c > +++ b/drivers/block/null_blk/main.c > @@ -157,6 +157,10 @@ static int g_max_sectors; > module_param_named(max_sectors, g_max_sectors, int, 0444); > MODULE_PARM_DESC(max_sectors, "Maximum size of a command (in 512B sectors)"); > > +static unsigned int g_max_segment_size = BLK_MAX_SEGMENT_SIZE; > +module_param_named(max_segment_size, g_max_segment_size, int, 0444); > +MODULE_PARM_DESC(max_segment_size, "Maximum size of a segment in bytes"); > + > static unsigned int nr_devices = 1; > module_param(nr_devices, uint, 0444); > MODULE_PARM_DESC(nr_devices, "Number of devices to register"); > @@ -409,6 +413,7 @@ NULLB_DEVICE_ATTR(home_node, uint, NULL); > NULLB_DEVICE_ATTR(queue_mode, uint, NULL); > NULLB_DEVICE_ATTR(blocksize, uint, NULL); > NULLB_DEVICE_ATTR(max_sectors, uint, NULL); > +NULLB_DEVICE_ATTR(max_segment_size, uint, NULL); > NULLB_DEVICE_ATTR(irqmode, uint, NULL); > NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL); > NULLB_DEVICE_ATTR(index, uint, NULL); > @@ -550,6 +555,7 @@ static struct configfs_attribute *nullb_device_attrs[] = { > &nullb_device_attr_queue_mode, > &nullb_device_attr_blocksize, > &nullb_device_attr_max_sectors, > + &nullb_device_attr_max_segment_size, > &nullb_device_attr_irqmode, > &nullb_device_attr_hw_queue_depth, > &nullb_device_attr_index, > @@ -652,7 +658,8 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page) > return snprintf(page, PAGE_SIZE, > "badblocks,blocking,blocksize,cache_size," > "completion_nsec,discard,home_node,hw_queue_depth," > - "irqmode,max_sectors,mbps,memory_backed,no_sched," > + "irqmode,max_sectors,max_segment_size,mbps," > + "memory_backed,no_sched," > "poll_queues,power,queue_mode,shared_tag_bitmap,size," > "submit_queues,use_per_node_hctx,virt_boundary,zoned," > "zone_capacity,zone_max_active,zone_max_open," > @@ -722,6 +729,7 @@ static struct nullb_device *null_alloc_dev(void) > dev->queue_mode = g_queue_mode; > dev->blocksize = g_bs; > dev->max_sectors = g_max_sectors; > + dev->max_segment_size = g_max_segment_size; > dev->irqmode = g_irqmode; > dev->hw_queue_depth = g_hw_queue_depth; > dev->blocking = g_blocking; > @@ -1248,6 +1256,8 @@ static int null_transfer(struct nullb *nullb, struct page *page, > unsigned int valid_len = len; > int err = 0; > > + WARN_ONCE(len > dev->max_segment_size, "%u > %u\n", len, > + dev->max_segment_size); > if (!is_write) { > if (dev->zoned) > valid_len = null_zone_valid_read_len(nullb, > @@ -1283,7 +1293,8 @@ static int null_handle_rq(struct nullb_cmd *cmd) > > spin_lock_irq(&nullb->lock); > rq_for_each_segment(bvec, rq, iter) { > - len = bvec.bv_len; > + len = min(bvec.bv_len, nullb->dev->max_segment_size); > + bvec.bv_len = len; I am still confused by this change... Why is it necessary ? If max_segment_size is set correctly, how can we ever get a BIO with a bvec length exceeding that maximum ? If that is the case, aren't we missing a bio_split() somewhere ? > err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset, > op_is_write(req_op(rq)), sector, > rq->cmd_flags & REQ_FUA); > @@ -1310,7 +1321,8 @@ static int null_handle_bio(struct nullb_cmd *cmd) > > spin_lock_irq(&nullb->lock); > bio_for_each_segment(bvec, bio, iter) { > - len = bvec.bv_len; > + len = min(bvec.bv_len, nullb->dev->max_segment_size); > + bvec.bv_len = len; > err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset, > op_is_write(bio_op(bio)), sector, > bio->bi_opf & REQ_FUA); > @@ -2161,6 +2173,7 @@ static int null_add_dev(struct nullb_device *dev) > dev->max_sectors = queue_max_hw_sectors(nullb->q); > dev->max_sectors = min(dev->max_sectors, BLK_DEF_MAX_SECTORS); > blk_queue_max_hw_sectors(nullb->q, dev->max_sectors); > + blk_queue_max_segment_size(nullb->q, dev->max_segment_size); > > if (dev->virt_boundary) > blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1); > diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h > index 929f659dd255..7bf80b0035f5 100644 > --- a/drivers/block/null_blk/null_blk.h > +++ b/drivers/block/null_blk/null_blk.h > @@ -107,6 +107,7 @@ struct nullb_device { > unsigned int queue_mode; /* block interface */ > unsigned int blocksize; /* block size */ > unsigned int max_sectors; /* Max sectors per command */ > + unsigned int max_segment_size; /* Max size of a single DMA segment. */ > unsigned int irqmode; /* IRQ completion handler */ > unsigned int hw_queue_depth; /* queue depth */ > unsigned int index; /* index of the disk, only valid with a disk */
On 6/12/23 15:17, Damien Le Moal wrote: > On 6/13/23 05:33, Bart Van Assche wrote: >> @@ -1283,7 +1293,8 @@ static int null_handle_rq(struct nullb_cmd *cmd) >> >> spin_lock_irq(&nullb->lock); >> rq_for_each_segment(bvec, rq, iter) { >> - len = bvec.bv_len; >> + len = min(bvec.bv_len, nullb->dev->max_segment_size); >> + bvec.bv_len = len; > > I am still confused by this change... Why is it necessary ? If max_segment_size > is set correctly, how can we ever get a BIO with a bvec length exceeding that > maximum ? If that is the case, aren't we missing a bio_split() somewhere ? Hi Damien, bio_split() enforces the max_sectors limit but not the max_segment_size limit. __blk_rq_map_sg() enforces the max_segment_size limit. null_blk does not call __blk_rq_map_sg(). Hence the above code to enforce the max_segment_size limit. Thanks, Bart.
On 6/13/23 09:44, Bart Van Assche wrote: > On 6/12/23 15:17, Damien Le Moal wrote: >> On 6/13/23 05:33, Bart Van Assche wrote: >>> @@ -1283,7 +1293,8 @@ static int null_handle_rq(struct nullb_cmd *cmd) >>> >>> spin_lock_irq(&nullb->lock); >>> rq_for_each_segment(bvec, rq, iter) { >>> - len = bvec.bv_len; >>> + len = min(bvec.bv_len, nullb->dev->max_segment_size); >>> + bvec.bv_len = len; >> >> I am still confused by this change... Why is it necessary ? If max_segment_size >> is set correctly, how can we ever get a BIO with a bvec length exceeding that >> maximum ? If that is the case, aren't we missing a bio_split() somewhere ? > > Hi Damien, > > bio_split() enforces the max_sectors limit but not the max_segment_size > limit. __blk_rq_map_sg() enforces the max_segment_size limit. null_blk > does not call __blk_rq_map_sg(). Hence the above code to enforce the > max_segment_size limit. OK. That is where I was confused :) Thanks ! > > Thanks, > > Bart. >
On Mon, Jun 12, 2023 at 05:44:51PM -0700, Bart Van Assche wrote: > > Hi Damien, > > bio_split() enforces the max_sectors limit but not the max_segment_size > limit. bio_split() doesn't enforce any limit, but it's also not used by null_blk or blk-mq. bio_split_to_limits enforces max_segment_size in bvec_split_segs.
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index b3fedafe301e..9c9098f1bd52 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -157,6 +157,10 @@ static int g_max_sectors; module_param_named(max_sectors, g_max_sectors, int, 0444); MODULE_PARM_DESC(max_sectors, "Maximum size of a command (in 512B sectors)"); +static unsigned int g_max_segment_size = BLK_MAX_SEGMENT_SIZE; +module_param_named(max_segment_size, g_max_segment_size, int, 0444); +MODULE_PARM_DESC(max_segment_size, "Maximum size of a segment in bytes"); + static unsigned int nr_devices = 1; module_param(nr_devices, uint, 0444); MODULE_PARM_DESC(nr_devices, "Number of devices to register"); @@ -409,6 +413,7 @@ NULLB_DEVICE_ATTR(home_node, uint, NULL); NULLB_DEVICE_ATTR(queue_mode, uint, NULL); NULLB_DEVICE_ATTR(blocksize, uint, NULL); NULLB_DEVICE_ATTR(max_sectors, uint, NULL); +NULLB_DEVICE_ATTR(max_segment_size, uint, NULL); NULLB_DEVICE_ATTR(irqmode, uint, NULL); NULLB_DEVICE_ATTR(hw_queue_depth, uint, NULL); NULLB_DEVICE_ATTR(index, uint, NULL); @@ -550,6 +555,7 @@ static struct configfs_attribute *nullb_device_attrs[] = { &nullb_device_attr_queue_mode, &nullb_device_attr_blocksize, &nullb_device_attr_max_sectors, + &nullb_device_attr_max_segment_size, &nullb_device_attr_irqmode, &nullb_device_attr_hw_queue_depth, &nullb_device_attr_index, @@ -652,7 +658,8 @@ static ssize_t memb_group_features_show(struct config_item *item, char *page) return snprintf(page, PAGE_SIZE, "badblocks,blocking,blocksize,cache_size," "completion_nsec,discard,home_node,hw_queue_depth," - "irqmode,max_sectors,mbps,memory_backed,no_sched," + "irqmode,max_sectors,max_segment_size,mbps," + "memory_backed,no_sched," "poll_queues,power,queue_mode,shared_tag_bitmap,size," "submit_queues,use_per_node_hctx,virt_boundary,zoned," "zone_capacity,zone_max_active,zone_max_open," @@ -722,6 +729,7 @@ static struct nullb_device *null_alloc_dev(void) dev->queue_mode = g_queue_mode; dev->blocksize = g_bs; dev->max_sectors = g_max_sectors; + dev->max_segment_size = g_max_segment_size; dev->irqmode = g_irqmode; dev->hw_queue_depth = g_hw_queue_depth; dev->blocking = g_blocking; @@ -1248,6 +1256,8 @@ static int null_transfer(struct nullb *nullb, struct page *page, unsigned int valid_len = len; int err = 0; + WARN_ONCE(len > dev->max_segment_size, "%u > %u\n", len, + dev->max_segment_size); if (!is_write) { if (dev->zoned) valid_len = null_zone_valid_read_len(nullb, @@ -1283,7 +1293,8 @@ static int null_handle_rq(struct nullb_cmd *cmd) spin_lock_irq(&nullb->lock); rq_for_each_segment(bvec, rq, iter) { - len = bvec.bv_len; + len = min(bvec.bv_len, nullb->dev->max_segment_size); + bvec.bv_len = len; err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset, op_is_write(req_op(rq)), sector, rq->cmd_flags & REQ_FUA); @@ -1310,7 +1321,8 @@ static int null_handle_bio(struct nullb_cmd *cmd) spin_lock_irq(&nullb->lock); bio_for_each_segment(bvec, bio, iter) { - len = bvec.bv_len; + len = min(bvec.bv_len, nullb->dev->max_segment_size); + bvec.bv_len = len; err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset, op_is_write(bio_op(bio)), sector, bio->bi_opf & REQ_FUA); @@ -2161,6 +2173,7 @@ static int null_add_dev(struct nullb_device *dev) dev->max_sectors = queue_max_hw_sectors(nullb->q); dev->max_sectors = min(dev->max_sectors, BLK_DEF_MAX_SECTORS); blk_queue_max_hw_sectors(nullb->q, dev->max_sectors); + blk_queue_max_segment_size(nullb->q, dev->max_segment_size); if (dev->virt_boundary) blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1); diff --git a/drivers/block/null_blk/null_blk.h b/drivers/block/null_blk/null_blk.h index 929f659dd255..7bf80b0035f5 100644 --- a/drivers/block/null_blk/null_blk.h +++ b/drivers/block/null_blk/null_blk.h @@ -107,6 +107,7 @@ struct nullb_device { unsigned int queue_mode; /* block interface */ unsigned int blocksize; /* block size */ unsigned int max_sectors; /* Max sectors per command */ + unsigned int max_segment_size; /* Max size of a single DMA segment. */ unsigned int irqmode; /* IRQ completion handler */ unsigned int hw_queue_depth; /* queue depth */ unsigned int index; /* index of the disk, only valid with a disk */