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authorMike Snitzer <snitzer@redhat.com>2011-02-11 11:05:46 +0100
committerJens Axboe <jaxboe@fusionio.com>2011-02-11 11:05:46 +0100
commit9d5a4e946ce5352f19400b6370f4cd8e72806278 (patch)
treeba62a2ab56da1f943b0dbcae527c70b817a104de
parentae1b1539622fb46e51b4d13b3f9e5f4c713f86ae (diff)
block: skip elevator data initialization for flush requests
Skip elevator initialization for flush requests by passing priv=0 to blk_alloc_request() in get_request(). As such elv_set_request() is never called for flush requests. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
-rw-r--r--block/blk-core.c29
1 files changed, 25 insertions, 4 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 05746093b45e..ab4a7696956d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -738,6 +738,25 @@ static void freed_request(struct request_queue *q, int sync, int priv)
}
/*
+ * Determine if elevator data should be initialized when allocating the
+ * request associated with @bio.
+ */
+static bool blk_rq_should_init_elevator(struct bio *bio)
+{
+ if (!bio)
+ return true;
+
+ /*
+ * Flush requests do not use the elevator so skip initialization.
+ * This allows a request to share the flush and elevator data.
+ */
+ if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
+ return false;
+
+ return true;
+}
+
+/*
* Get a free request, queue_lock must be held.
* Returns NULL on failure, with queue_lock held.
* Returns !NULL on success, with queue_lock *not held*.
@@ -749,7 +768,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
struct request_list *rl = &q->rq;
struct io_context *ioc = NULL;
const bool is_sync = rw_is_sync(rw_flags) != 0;
- int may_queue, priv;
+ int may_queue, priv = 0;
may_queue = elv_may_queue(q, rw_flags);
if (may_queue == ELV_MQUEUE_NO)
@@ -793,9 +812,11 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
rl->count[is_sync]++;
rl->starved[is_sync] = 0;
- priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
- if (priv)
- rl->elvpriv++;
+ if (blk_rq_should_init_elevator(bio)) {
+ priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+ if (priv)
+ rl->elvpriv++;
+ }
if (blk_queue_io_stat(q))
rw_flags |= REQ_IO_STAT;