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author | Jeff Moyer <jmoyer@redhat.com> | 2015-05-08 10:51:30 -0700 |
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committer | Jens Axboe <axboe@fb.com> | 2015-05-08 14:17:17 -0600 |
commit | e6c4438ba7cb615448492849970aaf0aaa1cc973 (patch) | |
tree | bf7e99da1027c03a29552b19873dec52de0b8050 /block/blk-ioc.c | |
parent | 5596d0d591bea25424c07f0fce00df5af593b31f (diff) |
blk-mq: fix plugging in blk_sq_make_request
The following appears in blk_sq_make_request:
/*
* If we have multiple hardware queues, just go directly to
* one of those for sync IO.
*/
We clearly don't have multiple hardware queues, here! This comment was
introduced with this commit 07068d5b8e (blk-mq: split make request
handler for multi and single queue):
We want slightly different behavior from them:
- On single queue devices, we currently use the per-process plug
for deferred IO and for merging.
- On multi queue devices, we don't use the per-process plug, but
we want to go straight to hardware for SYNC IO.
The old code had this:
use_plug = !is_flush_fua && ((q->nr_hw_queues == 1) || !is_sync);
and that was converted to:
use_plug = !is_flush_fua && !is_sync;
which is not equivalent. For the single queue case, that second half of
the && expression is always true. So, what I think was actually inteded
follows (and this more closely matches what is done in blk_queue_bio).
V2: delete the 'likely', which should not be a big deal
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-ioc.c')
0 files changed, 0 insertions, 0 deletions