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| author | Jeff Moyer <jmoyer@redhat.com> | 2011-08-09 20:32:09 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2011-08-09 20:32:09 +0200 |
| commit | fa1bf42ff9296ac4cf211b0a1b450a6071d26a95 (patch) | |
| tree | 0c7f43ca005c70022e64abb8b8d0b0d549b73959 /block/blk-flush.c | |
| parent | 4931402a9dd00b2997e95bfbb89409b2a6dbb383 (diff) | |
| download | lwn-fa1bf42ff9296ac4cf211b0a1b450a6071d26a95.tar.gz lwn-fa1bf42ff9296ac4cf211b0a1b450a6071d26a95.zip | |
allow blk_flush_policy to return REQ_FSEQ_DATA independent of *FLUSH
blk_insert_flush has the following check:
/*
* If there's data but flush is not necessary, the request can be
* processed directly without going through flush machinery. Queue
* for normal execution.
*/
if ((policy & REQ_FSEQ_DATA) &&
!(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
list_add_tail(&rq->queuelist, &q->queue_head);
return;
}
However, blk_flush_policy will not return with policy set to only
REQ_FSEQ_DATA:
static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
{
unsigned int policy = 0;
if (fflags & REQ_FLUSH) {
if (rq->cmd_flags & REQ_FLUSH)
policy |= REQ_FSEQ_PREFLUSH;
if (blk_rq_sectors(rq))
policy |= REQ_FSEQ_DATA;
if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA))
policy |= REQ_FSEQ_POSTFLUSH;
}
return policy;
}
Notice that REQ_FSEQ_DATA is only set if REQ_FLUSH is set. Fix this
mismatch by moving the setting of REQ_FSEQ_DATA outside of the REQ_FLUSH
check.
Tejun notes:
Hmmm... yes, this can become a correctness issue if (and only if)
blk_queue_flush() is called to change q->flush_flags while requests
are in-flight; otherwise, requests wouldn't reach the function at all.
Also, I think it would be a generally good idea to always set
FSEQ_DATA if the request has data.
Cheers,
Jeff
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block/blk-flush.c')
| -rw-r--r-- | block/blk-flush.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c index bb21e4c36f70..2d162bd840d3 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -95,11 +95,12 @@ static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq) { unsigned int policy = 0; + if (blk_rq_sectors(rq)) + policy |= REQ_FSEQ_DATA; + if (fflags & REQ_FLUSH) { if (rq->cmd_flags & REQ_FLUSH) policy |= REQ_FSEQ_PREFLUSH; - if (blk_rq_sectors(rq)) - policy |= REQ_FSEQ_DATA; if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA)) policy |= REQ_FSEQ_POSTFLUSH; } |