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authorTejun Heo <tj@kernel.org>2011-03-02 08:48:06 -0500
committerJens Axboe <jaxboe@fusionio.com>2011-03-02 08:48:06 -0500
commit255bb490c8c27eed484d538efe6ef6a7473bd3f6 (patch)
tree630289b9de253a1f0575f29d2de019494016ff79 /block
parent1654e7411a1ad4999fe7890ef51d2a2bbb1fcf76 (diff)
block: blk-flush shouldn't call directly into q->request_fn() __blk_run_queue()
blk-flush decomposes a flush into sequence of multiple requests. On completion of a request, the next one is queued; however, block layer must not implicitly call into q->request_fn() directly from completion path. This makes the queue behave unexpectedly when seen from the drivers and violates the assumption that q->request_fn() is called with process context + queue_lock. This patch makes blk-flush the following two changes to make sure q->request_fn() is not called directly from request completion path. - blk_flush_complete_seq_end_io() now asks __blk_run_queue() to always use kblockd instead of calling directly into q->request_fn(). - queue_next_fseq() uses ELEVATOR_INSERT_REQUEUE instead of ELEVATOR_INSERT_FRONT so that elv_insert() doesn't try to unplug the request queue directly. Reported by Jan in the following threads. http://thread.gmane.org/gmane.linux.ide/48778 http://thread.gmane.org/gmane.linux.ide/48786 stable: applicable to v2.6.37. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jan Beulich <JBeulich@novell.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-flush.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 56adaa8d55cd..b27d0208611b 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -66,10 +66,12 @@ static void blk_flush_complete_seq_end_io(struct request_queue *q,
66 66
67 /* 67 /*
68 * Moving a request silently to empty queue_head may stall the 68 * Moving a request silently to empty queue_head may stall the
69 * queue. Kick the queue in those cases. 69 * queue. Kick the queue in those cases. This function is called
70 * from request completion path and calling directly into
71 * request_fn may confuse the driver. Always use kblockd.
70 */ 72 */
71 if (was_empty && next_rq) 73 if (was_empty && next_rq)
72 __blk_run_queue(q, false); 74 __blk_run_queue(q, true);
73} 75}
74 76
75static void pre_flush_end_io(struct request *rq, int error) 77static void pre_flush_end_io(struct request *rq, int error)
@@ -130,7 +132,7 @@ static struct request *queue_next_fseq(struct request_queue *q)
130 BUG(); 132 BUG();
131 } 133 }
132 134
133 elv_insert(q, rq, ELEVATOR_INSERT_FRONT); 135 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
134 return rq; 136 return rq;
135} 137}
136 138