[PATCH 4.2.y-ckt 088/305] block: Always check queue limits for cloned requests

From: Kamal Mostafa
Date: Fri Jan 15 2016 - 20:10:12 EST

4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know.


From: Hannes Reinecke <hare@xxxxxxx>

commit bf4e6b4e757488dee1b6a581f49c7ac34cd217f8 upstream.

When a cloned request is retried on other queues it always needs
to be checked against the queue limits of that queue.
Otherwise the calculations for nr_phys_segments might be wrong,
leading to a crash in scsi_init_sgtable().

To clarify this the patch renames blk_rq_check_limits()
to blk_cloned_rq_check_limits() and removes the symbol
export, as the new function should only be used for
cloned requests and never exported.

Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: Ewan Milne <emilne@xxxxxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Fixes: e2a60da74 ("block: Clean up special command handling logic")
Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
block/blk-core.c | 21 +++++++--------------
include/linux/blkdev.h | 1 -
2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 1955ed3..56c08e1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2023,7 +2023,8 @@ void submit_bio(int rw, struct bio *bio)

- * blk_rq_check_limits - Helper function to check a request for the queue limit
+ * blk_cloned_rq_check_limits - Helper function to check a cloned request
+ * for new the queue limits
* @q: the queue
* @rq: the request being checked
@@ -2034,20 +2035,13 @@ EXPORT_SYMBOL(submit_bio);
* after it is inserted to @q, it should be checked against @q before
* the insertion using this generic function.
- * This function should also be useful for request stacking drivers
- * in some cases below, so export this function.
* Request stacking drivers like request-based dm may change the queue
- * limits while requests are in the queue (e.g. dm's table swapping).
- * Such request stacking drivers should check those requests against
- * the new queue limits again when they dispatch those requests,
- * although such checkings are also done against the old queue limits
- * when submitting requests.
+ * limits when retrying requests on other queues. Those requests need
+ * to be checked against the new queue limits again during dispatch.
-int blk_rq_check_limits(struct request_queue *q, struct request *rq)
+static int blk_cloned_rq_check_limits(struct request_queue *q,
+ struct request *rq)
- if (!rq_mergeable(rq))
- return 0;
if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
printk(KERN_ERR "%s: over max size limit.\n", __func__);
return -EIO;
@@ -2067,7 +2061,6 @@ int blk_rq_check_limits(struct request_queue *q, struct request *rq)

return 0;

* blk_insert_cloned_request - Helper for stacking drivers to submit a request
@@ -2079,7 +2072,7 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
unsigned long flags;

- if (blk_rq_check_limits(q, rq))
+ if (blk_cloned_rq_check_limits(q, rq))
return -EIO;

if (rq->rq_disk &&
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d4068c1..f8d6f12 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -772,7 +772,6 @@ extern void blk_rq_set_block_pc(struct request *);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern void blk_add_request_payload(struct request *rq, struct page *page,
unsigned int len);
-extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
extern int blk_lld_busy(struct request_queue *q);
extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
struct bio_set *bs, gfp_t gfp_mask,