[PATCH 2/5] [PATCH 2/5] revert: "blk-mq: blk-mq should free bios in pass throughcase"

[Christoph Hellwig]

This patch causes boot failures when using REQ_FLUSH requests.  Also the
following statement in the commit log:

    For non mq calls, the block layer will free the bios when
    blk_finish_request is called.

    For mq calls, the blk mq code wants the caller to do this.

Seems incorrect as far as I can follow the code as blk_finish_request only
calls __blk_put_request which then completes the bios if req->end_io is
not set.  This matches the blk-mq behaviour before this patch, so reverting
it makes the code more similar to the legacy case in addition to fixing the
boot failure.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 block/blk-flush.c |    2 +-
 block/blk-mq.c    |   14 ++++++++++----
 block/blk-mq.h    |    1 +
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 3e4cc9c..c56c37d 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -231,7 +231,7 @@ static void flush_end_io(struct request *flush_rq, int error)
 	unsigned long flags = 0;
 
 	if (q->mq_ops) {
-		blk_mq_free_request(flush_rq);
+		blk_mq_finish_request(flush_rq, error);
 		spin_lock_irqsave(&q->mq_flush_lock, flags);
 	}
 	running = &q->flush_queue[q->flush_running_idx];
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 93563e0..423089d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -270,7 +270,7 @@ void blk_mq_free_request(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_free_request);
 
-static void blk_mq_finish_request(struct request *rq, int error)
+void blk_mq_finish_request(struct request *rq, int error)
 {
 	struct bio *bio = rq->bio;
 	unsigned int bytes = 0;
@@ -286,17 +286,22 @@ static void blk_mq_finish_request(struct request *rq, int error)
 
 	blk_account_io_completion(rq, bytes);
 	blk_account_io_done(rq);
+	blk_mq_free_request(rq);
 }
 
 void blk_mq_complete_request(struct request *rq, int error)
 {
 	trace_block_rq_complete(rq->q, rq);
-	blk_mq_finish_request(rq, error);
 
+	/*
+	 * If ->end_io is set, it's responsible for doing the rest of the
+	 * completion.
+	 */
 	if (rq->end_io)
 		rq->end_io(rq, error);
 	else
-		blk_mq_free_request(rq);
+		blk_mq_finish_request(rq, error);
+
 }
 
 void __blk_mq_end_io(struct request *rq, int error)
@@ -984,7 +989,8 @@ int blk_mq_execute_rq(struct request_queue *q, struct request *rq)
 	if (rq->errors)
 		err = -EIO;
 
-	blk_mq_free_request(rq);
+	blk_mq_finish_request(rq, rq->errors);
+
 	return err;
 }
 EXPORT_SYMBOL(blk_mq_execute_rq);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 52bf1f9..42d0110 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -27,6 +27,7 @@ void blk_mq_complete_request(struct request *rq, int error);
 void blk_mq_run_request(struct request *rq, bool run_queue, bool async);
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_init_flush(struct request_queue *q);
+void blk_mq_finish_request(struct request *rq, int error);
 
 /*
  * CPU hotplug helpers
-- 
1.7.10.4


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