linux-kernel - [PATCH 4.3 011/200] block: Always check queue limits for cloned requests

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Message-Id: <20160214222217.516510411@linuxfoundation.org>
Date:	Sun, 14 Feb 2016 14:20:18 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Mike Snitzer <snitzer@...hat.com>,
	Ewan Milne <emilne@...hat.com>, Jeff Moyer <jmoyer@...hat.com>,
	Hannes Reinecke <hare@...e.de>, Jens Axboe <axboe@...com>
Subject: [PATCH 4.3 011/200] block: Always check queue limits for cloned requests

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

------------------

From: Hannes Reinecke <hare@...e.de>

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@...hat.com>
Cc: Ewan Milne <emilne@...hat.com>
Cc: Jeff Moyer <jmoyer@...hat.com>
Signed-off-by: Hannes Reinecke <hare@...e.de>
Fixes: e2a60da74 ("block: Clean up special command handling logic")
Acked-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-core.c       |   21 +++++++--------------
 include/linux/blkdev.h |    1 -
 2 files changed, 7 insertions(+), 15 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2023,7 +2023,8 @@ void submit_bio(int rw, struct bio *bio)
 EXPORT_SYMBOL(submit_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_q
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(blk_rq_check_limits);
 
 /**
  * blk_insert_cloned_request - Helper for stacking drivers to submit a request
@@ -2079,7 +2072,7 @@ int blk_insert_cloned_request(struct req
 	unsigned long flags;
 	int where = ELEVATOR_INSERT_BACK;
 
-	if (blk_rq_check_limits(q, rq))
+	if (blk_cloned_rq_check_limits(q, rq))
 		return -EIO;
 
 	if (rq->rq_disk &&
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -767,7 +767,6 @@ extern void blk_rq_set_block_pc(struct r
 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,