linux-kernel - Re: bio linked list corruption.

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Date:   Wed, 26 Oct 2016 23:33:56 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jens Axboe <axboe@...com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Jones <davej@...emonkey.org.uk>, Chris Mason <clm@...com>,
        Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Dave Chinner <david@...morbit.com>
Subject: Re: bio linked list corruption.

> Dave, can you hit the warnings with this? Totally untested...

Can we just kill off the unhelpful blk_map_ctx structure, e.g.:


diff --git a/block/blk-mq.c b/block/blk-mq.c
index ddc2eed..d74a74a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1190,21 +1190,15 @@ static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
 	}
 }
 
-struct blk_map_ctx {
-	struct blk_mq_hw_ctx *hctx;
-	struct blk_mq_ctx *ctx;
-};
-
 static struct request *blk_mq_map_request(struct request_queue *q,
 					  struct bio *bio,
-					  struct blk_map_ctx *data)
+					  struct blk_mq_alloc_data *data)
 {
 	struct blk_mq_hw_ctx *hctx;
 	struct blk_mq_ctx *ctx;
 	struct request *rq;
 	int op = bio_data_dir(bio);
 	int op_flags = 0;
-	struct blk_mq_alloc_data alloc_data;
 
 	blk_queue_enter_live(q);
 	ctx = blk_mq_get_ctx(q);
@@ -1214,12 +1208,10 @@ static struct request *blk_mq_map_request(struct request_queue *q,
 		op_flags |= REQ_SYNC;
 
 	trace_block_getrq(q, bio, op);
-	blk_mq_set_alloc_data(&alloc_data, q, 0, ctx, hctx);
-	rq = __blk_mq_alloc_request(&alloc_data, op, op_flags);
+	blk_mq_set_alloc_data(data, q, 0, ctx, hctx);
+	rq = __blk_mq_alloc_request(data, op, op_flags);
 
-	hctx->queued++;
-	data->hctx = hctx;
-	data->ctx = ctx;
+	data->hctx->queued++;
 	return rq;
 }
 
@@ -1267,7 +1259,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 {
 	const int is_sync = rw_is_sync(bio_op(bio), bio->bi_opf);
 	const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
-	struct blk_map_ctx data;
+	struct blk_mq_alloc_data data;
 	struct request *rq;
 	unsigned int request_count = 0;
 	struct blk_plug *plug;
@@ -1363,7 +1355,7 @@ static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
 	const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
 	struct blk_plug *plug;
 	unsigned int request_count = 0;
-	struct blk_map_ctx data;
+	struct blk_mq_alloc_data data;
 	struct request *rq;
 	blk_qc_t cookie;