block: introduce REQ_FLUSH flag (8749534f) · Commits · 戴 / test

SCSI-ml needs a way to mark a request as flush request in q->prepare_flush_fn because it needs to identify them later (e.g. in q->request_fn or prep_rq_fn). queue_flush sets REQ_HARDBARRIER in rq->cmd_flags however the block layer also sends normal REQ_TYPE_FS requests with REQ_HARDBARRIER. So SCSI-ml can't use REQ_HARDBARRIER to identify flush requests. We could change the block layer to clear REQ_HARDBARRIER bit before sending non flush requests to the lower layers. However, intorudcing the new flag looks cleaner (surely easier). Signed-off-by:

FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: James Bottomley <James.Bottomley@suse.de> Cc: David S. Miller <davem@davemloft.net> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Alasdair G Kergon <agk@redhat.com> Reviewed-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Jens Axboe <jaxboe@fusionio.com>

block/blk-barrier.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -143,7 +143,7 @@ static void queue_flush(struct request_queue *q, unsigned which)
		}

		blk_rq_init(q, rq);
		rq->cmd_flags = REQ_HARDBARRIER;
		rq->cmd_flags = REQ_HARDBARRIER \| REQ_FLUSH;
		rq->rq_disk = q->bar_rq.rq_disk;
		rq->end_io = end_io;
		q->prepare_flush_fn(q, rq);

include/linux/bio.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -174,6 +174,7 @@ enum rq_flag_bits {
		__REQ_ALLOCED, /* request came from our alloc pool */
		__REQ_COPY_USER, /* contains copies of user pages */
		__REQ_INTEGRITY, /* integrity metadata has been remapped */
		__REQ_FLUSH, /* request for cache flush */
		__REQ_IO_STAT, /* account I/O stat */
		__REQ_MIXED_MERGE, /* merge of different types, fail separately */
		__REQ_NR_BITS, /* stops here */
		@@ -213,6 +214,7 @@ enum rq_flag_bits {
		#define REQ_ALLOCED (1 << __REQ_ALLOCED)
		#define REQ_COPY_USER (1 << __REQ_COPY_USER)
		#define REQ_INTEGRITY (1 << __REQ_INTEGRITY)
		#define REQ_FLUSH (1 << __REQ_FLUSH)
		#define REQ_IO_STAT (1 << __REQ_IO_STAT)
		#define REQ_MIXED_MERGE (1 << __REQ_MIXED_MERGE)

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