[dm-devel] [PATCH] blk-mq: enforce op-specific segment limits in blk_insert_cloned_request
Uday Shankar
ushankar at purestorage.com
Wed Feb 15 20:15:08 UTC 2023
The block layer might merge together discard requests up until the
max_discard_segments limit is hit, but blk_insert_cloned_request checks
the segment count against max_segments regardless of the req op. This
can result in errors like the following when discards are issued through
a DM device and max_discard_segments exceeds max_segments for the queue
of the chosen underlying device.
blk_insert_cloned_request: over max segments limit. (256 > 129)
Fix this by looking at the req_op and enforcing the appropriate segment
limit - max_discard_segments for REQ_OP_DISCARDs and max_segments for
everything else.
Signed-off-by: Uday Shankar <ushankar at purestorage.com>
---
block/blk-merge.c | 4 +---
block/blk-mq.c | 5 +++--
block/blk.h | 8 ++++++++
3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index b7c193d67..7f663c2d3 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -588,9 +588,7 @@ EXPORT_SYMBOL(__blk_rq_map_sg);
static inline unsigned int blk_rq_get_max_segments(struct request *rq)
{
- if (req_op(rq) == REQ_OP_DISCARD)
- return queue_max_discard_segments(rq->q);
- return queue_max_segments(rq->q);
+ return blk_queue_get_max_segments(rq->q, req_op(rq));
}
static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index d3494a796..121b20230 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3000,6 +3000,7 @@ blk_status_t blk_insert_cloned_request(struct request *rq)
{
struct request_queue *q = rq->q;
unsigned int max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
+ unsigned int max_segments = blk_queue_get_max_segments(q, req_op(rq));
blk_status_t ret;
if (blk_rq_sectors(rq) > max_sectors) {
@@ -3026,9 +3027,9 @@ blk_status_t blk_insert_cloned_request(struct request *rq)
* original queue.
*/
rq->nr_phys_segments = blk_recalc_rq_segments(rq);
- if (rq->nr_phys_segments > queue_max_segments(q)) {
+ if (rq->nr_phys_segments > max_segments) {
printk(KERN_ERR "%s: over max segments limit. (%hu > %hu)\n",
- __func__, rq->nr_phys_segments, queue_max_segments(q));
+ __func__, rq->nr_phys_segments, max_segments);
return BLK_STS_IOERR;
}
diff --git a/block/blk.h b/block/blk.h
index f02381405..8d705c13a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -169,6 +169,14 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
return q->limits.max_sectors;
}
+static inline unsigned int blk_queue_get_max_segments(struct request_queue *q,
+ enum req_op op)
+{
+ if (op == REQ_OP_DISCARD)
+ return queue_max_discard_segments(q);
+ return queue_max_segments(q);
+}
+
#ifdef CONFIG_BLK_DEV_INTEGRITY
void blk_flush_integrity(void);
bool __bio_integrity_endio(struct bio *);
base-commit: 6bea9ac7c6481c09eb2b61d7cd844fc64a526e3e
--
2.25.1
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