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H A D | blk-flush.c | fa1bf42f Tue Aug 09 13:32:09 CDT 2011 Jeff Moyer <jmoyer@redhat.com> 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> fa1bf42f Tue Aug 09 13:32:09 CDT 2011 Jeff Moyer <jmoyer@redhat.com> 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>
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