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block/sd: Fix device-imposed transfer length limits

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Commit 4f258a4634 ("sd: Fix maximum I/O size for BLOCK_PC requests")
had the unfortunate side-effect of removing an implicit clamp to
BLK_DEF_MAX_SECTORS for REQ_TYPE_FS requests in the block layer
code. This caused problems for some SMR drives.

Debugging this issue revealed a few problems with the existing
infrastructure since the block layer didn't know how to deal with
device-imposed limits, only limits set by the I/O controller.

 - Introduce a new queue limit, max_dev_sectors, which is used by the
   ULD to signal the maximum sectors for a REQ_TYPE_FS request.

 - Ensure that max_dev_sectors is correctly stacked and taken into
   account when overriding max_sectors through sysfs.

 - Rework sd_read_block_limits() so it saves the max_xfer and opt_xfer
   values for later processing.

 - In sd_revalidate() set the queue's max_dev_sectors based on the
   MAXIMUM TRANSFER LENGTH value in the Block Limits VPD. If this value
   is not reported, fall back to a cap based on the CDB TRANSFER LENGTH
   field size.

 - In sd_revalidate(), use OPTIMAL TRANSFER LENGTH from the Block Limits
   VPD--if reported and sane--to signal the preferred device transfer
   size for FS requests. Otherwise use BLK_DEF_MAX_SECTORS.

 - blk_limits_max_hw_sectors() is no longer used and can be removed.

Signed-off-by: Martin K. Petersen <[email protected]>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=93581
Reviewed-by: Christoph Hellwig <[email protected]>
Tested-by: [email protected]
Tested-by: Arzeets <[email protected]>
Tested-by: David Eisner <[email protected]>
Tested-by: Mario Kicherer <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>
This commit is contained in:
Martin K. Petersen 2015-11-13 16:46:48 -05:00
commit ca369d51b3
5 changed files with 51 additions and 37 deletions
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36
block/blk-settings.c
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@ -91,7 +91,8 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
lim->virt_boundary_mask = 0;
lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
lim->max_sectors = lim->max_dev_sectors = lim->max_hw_sectors =
BLK_SAFE_MAX_SECTORS;
lim->chunk_sectors = 0;
lim->max_write_same_sectors = 0;
lim->max_discard_sectors = 0;
@ -127,6 +128,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
lim->max_hw_sectors = UINT_MAX;
lim->max_segment_size = UINT_MAX;
lim->max_sectors = UINT_MAX;
lim->max_dev_sectors = UINT_MAX;
lim->max_write_same_sectors = UINT_MAX;
}
EXPORT_SYMBOL(blk_set_stacking_limits);
@ -214,8 +216,8 @@ void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr)
EXPORT_SYMBOL(blk_queue_bounce_limit);
/**
* blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
* @limits: the queue limits
* blk_queue_max_hw_sectors - set max sectors for a request for this queue
* @q: the request queue for the device
* @max_hw_sectors: max hardware sectors in the usual 512b unit
*
* Description:
@ -224,13 +226,19 @@ EXPORT_SYMBOL(blk_queue_bounce_limit);
* the device driver based upon the capabilities of the I/O
* controller.
*
* max_dev_sectors is a hard limit imposed by the storage device for
* READ/WRITE requests. It is set by the disk driver.
*
* max_sectors is a soft limit imposed by the block layer for
* filesystem type requests. This value can be overridden on a
* per-device basis in /sys/block/<device>/queue/max_sectors_kb.
* The soft limit can not exceed max_hw_sectors.
**/
void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
{
struct queue_limits *limits = &q->limits;
unsigned int max_sectors;
if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
printk(KERN_INFO "%s: set to minimum %d\n",
@ -238,22 +246,9 @@ void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_
}
limits->max_hw_sectors = max_hw_sectors;
limits->max_sectors = min_t(unsigned int, max_hw_sectors,
BLK_DEF_MAX_SECTORS);
}
EXPORT_SYMBOL(blk_limits_max_hw_sectors);
/**
* blk_queue_max_hw_sectors - set max sectors for a request for this queue
* @q: the request queue for the device
* @max_hw_sectors: max hardware sectors in the usual 512b unit
*
* Description:
* See description for blk_limits_max_hw_sectors().
**/
void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
{
blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
limits->max_sectors = max_sectors;
}
EXPORT_SYMBOL(blk_queue_max_hw_sectors);
@ -527,6 +522,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
t->max_write_same_sectors = min(t->max_write_same_sectors,
b->max_write_same_sectors);
t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);