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authorMike Snitzer <snitzer@redhat.com>2020-11-30 10:57:43 -0500
committerMike Snitzer <snitzer@redhat.com>2020-12-04 14:53:15 -0500
commit3ee16db390b42b8a21f2ad2ea2518f3469c6e532 (patch)
tree2a34d72f6ef06b6708c8ae56577baa2c9506002b /include
parent857c4c0a8b2888d806f4308c58f59a6a81a1dee9 (diff)
dm: fix IO splitting
Commit 882ec4e609c1 ("dm table: stack 'chunk_sectors' limit to account for target-specific splitting") caused a couple regressions: 1) Using lcm_not_zero() when stacking chunk_sectors was a bug because chunk_sectors must reflect the most limited of all devices in the IO stack. 2) DM targets that set max_io_len but that do _not_ provide an .iterate_devices method no longer had there IO split properly. And commit 5091cdec56fa ("dm: change max_io_len() to use blk_max_size_offset()") also caused a regression where DM no longer supported varied (per target) IO splitting. The implication being the potential for severely reduced performance for IO stacks that use a DM target like dm-cache to hide performance limitations of a slower device (e.g. one that requires 4K IO splitting). Coming full circle: Fix all these issues by discontinuing stacking chunk_sectors up using ti->max_io_len in dm_calculate_queue_limits(), add optional chunk_sectors override argument to blk_max_size_offset() and update DM's max_io_len() to pass ti->max_io_len to its blk_max_size_offset() call. Passing in an optional chunk_sectors override to blk_max_size_offset() allows for code reuse of block's centralized calculation for max IO size based on provided offset and split boundary. Fixes: 882ec4e609c1 ("dm table: stack 'chunk_sectors' limit to account for target-specific splitting") Fixes: 5091cdec56fa ("dm: change max_io_len() to use blk_max_size_offset()") Cc: stable@vger.kernel.org Reported-by: John Dorminy <jdorminy@redhat.com> Reported-by: Bruce Johnston <bjohnsto@redhat.com> Reported-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: John Dorminy <jdorminy@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include')
-rw-r--r--include/linux/blkdev.h11
1 files changed, 6 insertions, 5 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 639cae2c158b..24ae504cf77d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1073,11 +1073,12 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
* file system requests.
*/
static inline unsigned int blk_max_size_offset(struct request_queue *q,
- sector_t offset)
+ sector_t offset,
+ unsigned int chunk_sectors)
{
- unsigned int chunk_sectors = q->limits.chunk_sectors;
-
- if (!chunk_sectors)
+ if (!chunk_sectors && q->limits.chunk_sectors)
+ chunk_sectors = q->limits.chunk_sectors;
+ else
return q->limits.max_sectors;
if (likely(is_power_of_2(chunk_sectors)))
@@ -1101,7 +1102,7 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
req_op(rq) == REQ_OP_SECURE_ERASE)
return blk_queue_get_max_sectors(q, req_op(rq));
- return min(blk_max_size_offset(q, offset),
+ return min(blk_max_size_offset(q, offset, 0),
blk_queue_get_max_sectors(q, req_op(rq)));
}