diff options
author | Tejun Heo <tj@kernel.org> | 2011-03-02 08:48:06 -0500 |
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committer | Jens Axboe <jaxboe@fusionio.com> | 2011-03-02 08:48:06 -0500 |
commit | 255bb490c8c27eed484d538efe6ef6a7473bd3f6 (patch) | |
tree | 630289b9de253a1f0575f29d2de019494016ff79 /block/blk-flush.c | |
parent | 1654e7411a1ad4999fe7890ef51d2a2bbb1fcf76 (diff) | |
download | lwn-255bb490c8c27eed484d538efe6ef6a7473bd3f6.tar.gz lwn-255bb490c8c27eed484d538efe6ef6a7473bd3f6.zip |
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/blk-flush.c')
-rw-r--r-- | block/blk-flush.c | 8 |
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, /* * Moving a request silently to empty queue_head may stall the - * queue. Kick the queue in those cases. + * queue. Kick the queue in those cases. This function is called + * from request completion path and calling directly into + * request_fn may confuse the driver. Always use kblockd. */ if (was_empty && next_rq) - __blk_run_queue(q, false); + __blk_run_queue(q, true); } static void pre_flush_end_io(struct request *rq, int error) @@ -130,7 +132,7 @@ static struct request *queue_next_fseq(struct request_queue *q) BUG(); } - elv_insert(q, rq, ELEVATOR_INSERT_FRONT); + elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE); return rq; } |