[PATCH v1 1/5] block: blk-mq: avoid initializing request during its completion

[Ming Lei]

One problem is that request->start_time/start_time_ns could be
set as wrong.

Also it is normal to intialize one data structure just after its
allocation.

So move the initialization out of its completion path.

Cc: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Ming Lei <tom.leim...@gmail.com>
---
 block/blk-mq.c |   26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 53dc9f7..35ae189 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -82,6 +82,7 @@ static struct request *blk_mq_alloc_rq(struct blk_mq_hw_ctx 
*hctx, gfp_t gfp,
        tag = blk_mq_get_tag(hctx->tags, gfp, reserved);
        if (tag != BLK_MQ_TAG_FAIL) {
                rq = hctx->rqs[tag];
+               blk_rq_init(hctx->queue, rq);
                rq->tag = tag;
 
                return rq;
@@ -169,9 +170,13 @@ bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
 }
 EXPORT_SYMBOL(blk_mq_can_queue);
 
-static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx,
-                              struct request *rq, unsigned int rw_flags)
+static void blk_mq_rq_init(struct request_queue *q, struct blk_mq_ctx *ctx,
+                              struct blk_mq_hw_ctx *hctx, struct request *rq,
+                              unsigned int rw_flags)
 {
+       if (hctx->cmd_size)
+               rq->special = blk_mq_rq_to_pdu(rq);
+
        if (blk_queue_io_stat(q))
                rw_flags |= REQ_IO_STAT;
 
@@ -198,7 +203,7 @@ static struct request *blk_mq_alloc_request_pinned(struct 
request_queue *q,
 
                rq = __blk_mq_alloc_request(hctx, gfp & ~__GFP_WAIT, reserved);
                if (rq) {
-                       blk_mq_rq_ctx_init(q, ctx, rq, rw);
+                       blk_mq_rq_init(q, ctx, hctx, rq, rw);
                        break;
                }
 
@@ -242,24 +247,12 @@ struct request *blk_mq_alloc_reserved_request(struct 
request_queue *q, int rw,
 }
 EXPORT_SYMBOL(blk_mq_alloc_reserved_request);
 
-/*
- * Re-init and set pdu, if we have it
- */
-static void blk_mq_rq_init(struct blk_mq_hw_ctx *hctx, struct request *rq)
-{
-       blk_rq_init(hctx->queue, rq);
-
-       if (hctx->cmd_size)
-               rq->special = blk_mq_rq_to_pdu(rq);
-}
-
 static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
                                  struct blk_mq_ctx *ctx, struct request *rq)
 {
        const int tag = rq->tag;
        struct request_queue *q = rq->q;
 
-       blk_mq_rq_init(hctx, rq);
        blk_mq_put_tag(hctx->tags, tag);
 
        blk_mq_queue_exit(q);
@@ -889,7 +882,7 @@ static void blk_mq_make_request(struct request_queue *q, 
struct bio *bio)
        trace_block_getrq(q, bio, rw);
        rq = __blk_mq_alloc_request(hctx, GFP_ATOMIC, false);
        if (likely(rq))
-               blk_mq_rq_ctx_init(q, ctx, rq, rw);
+               blk_mq_rq_init(q, ctx, hctx, rq, rw);
        else {
                blk_mq_put_ctx(ctx);
                trace_block_sleeprq(q, bio, rw);
@@ -1123,7 +1116,6 @@ static int blk_mq_init_rq_map(struct blk_mq_hw_ctx *hctx,
                left -= to_do * rq_size;
                for (j = 0; j < to_do; j++) {
                        hctx->rqs[i] = p;
-                       blk_mq_rq_init(hctx, hctx->rqs[i]);
                        p += rq_size;
                        i++;
                }
-- 
1.7.9.5

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