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authorChristoph Hellwig <hch@infradead.org>2014-02-11 08:27:14 -0800
committerJens Axboe <axboe@fb.com>2014-02-11 09:34:08 -0700
commit49f5baa5109897b8cee491e8a7c4d74052b6bc1e (patch)
tree9e0cf5285be207bde015af948e8fd7b89760ffcd /block
parent1e93b8c274268038c93763dca65a73b42a081e10 (diff)
downloadlinux-49f5baa5109897b8cee491e8a7c4d74052b6bc1e.tar.gz
blk-mq: pair blk_mq_start_request / blk_mq_requeue_request
Make sure we have a proper pairing between starting and requeueing requests. Move the dma drain and REQ_END setup into blk_mq_start_request, and make sure blk_mq_requeue_request properly undoes them, giving us a pair of function to prepare and unprepare a request without leaving side effects. Together this ensures we always clean up properly after BLK_MQ_RQ_QUEUE_BUSY returns from ->queue_rq. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c49
1 files changed, 26 insertions, 23 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0480710a8b4..1fa9dd153fd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -377,7 +377,7 @@ void blk_mq_complete_request(struct request *rq)
}
EXPORT_SYMBOL(blk_mq_complete_request);
-static void blk_mq_start_request(struct request *rq)
+static void blk_mq_start_request(struct request *rq, bool last)
{
struct request_queue *q = rq->q;
@@ -390,6 +390,25 @@ static void blk_mq_start_request(struct request *rq)
*/
rq->deadline = jiffies + q->rq_timeout;
set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+
+ if (q->dma_drain_size && blk_rq_bytes(rq)) {
+ /*
+ * Make sure space for the drain appears. We know we can do
+ * this because max_hw_segments has been adjusted to be one
+ * fewer than the device can handle.
+ */
+ rq->nr_phys_segments++;
+ }
+
+ /*
+ * Flag the last request in the series so that drivers know when IO
+ * should be kicked off, if they don't do it on a per-request basis.
+ *
+ * Note: the flag isn't the only condition drivers should do kick off.
+ * If drive is busy, the last request might not have the bit set.
+ */
+ if (last)
+ rq->cmd_flags |= REQ_END;
}
static void blk_mq_requeue_request(struct request *rq)
@@ -398,6 +417,11 @@ static void blk_mq_requeue_request(struct request *rq)
trace_block_rq_requeue(q, rq);
clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+
+ rq->cmd_flags &= ~REQ_END;
+
+ if (q->dma_drain_size && blk_rq_bytes(rq))
+ rq->nr_phys_segments--;
}
struct blk_mq_timeout_data {
@@ -565,29 +589,8 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
rq = list_first_entry(&rq_list, struct request, queuelist);
list_del_init(&rq->queuelist);
- blk_mq_start_request(rq);
- if (q->dma_drain_size && blk_rq_bytes(rq)) {
- /*
- * make sure space for the drain appears we
- * know we can do this because max_hw_segments
- * has been adjusted to be one fewer than the
- * device can handle
- */
- rq->nr_phys_segments++;
- }
-
- /*
- * Last request in the series. Flag it as such, this
- * enables drivers to know when IO should be kicked off,
- * if they don't do it on a per-request basis.
- *
- * Note: the flag isn't the only condition drivers
- * should do kick off. If drive is busy, the last
- * request might not have the bit set.
- */
- if (list_empty(&rq_list))
- rq->cmd_flags |= REQ_END;
+ blk_mq_start_request(rq, list_empty(&rq_list));
ret = q->mq_ops->queue_rq(hctx, rq);
switch (ret) {