From 3228f48be2d19b2dd90db96ec16a40187a2946f3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 28 Oct 2013 13:33:58 -0600 Subject: blk-mq: fix for flush deadlock The flush state machine takes in a struct request, which then is submitted multiple times to the underling driver. The old block code requeses the same request for each of those, so it does not have an issue with tapping into the request pool. The new one on the other hand allocates a new request for each of the actualy steps of the flush sequence. If have already allocated all of the tags for IO, we will fail allocating the flush request. Set aside a reserved request just for flushes. Signed-off-by: Jens Axboe --- block/blk-core.c | 2 +- block/blk-flush.c | 2 +- block/blk-mq.c | 14 ++++++++++++-- 3 files changed, 14 insertions(+), 4 deletions(-) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index 3bb9e9f7f87..9677c6525ed 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1102,7 +1102,7 @@ static struct request *blk_old_get_request(struct request_queue *q, int rw, struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask) { if (q->mq_ops) - return blk_mq_alloc_request(q, rw, gfp_mask); + return blk_mq_alloc_request(q, rw, gfp_mask, false); else return blk_old_get_request(q, rw, gfp_mask); } diff --git a/block/blk-flush.c b/block/blk-flush.c index 3e4cc9c7890..331e627301e 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -286,7 +286,7 @@ static void mq_flush_work(struct work_struct *work) /* We don't need set REQ_FLUSH_SEQ, it's for consistency */ rq = blk_mq_alloc_request(q, WRITE_FLUSH|REQ_FLUSH_SEQ, - __GFP_WAIT|GFP_ATOMIC); + __GFP_WAIT|GFP_ATOMIC, true); rq->cmd_type = REQ_TYPE_FS; rq->end_io = flush_end_io; diff --git a/block/blk-mq.c b/block/blk-mq.c index ac804c63504..2dc8de86d0d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -210,14 +210,15 @@ static struct request *blk_mq_alloc_request_pinned(struct request_queue *q, return rq; } -struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp) +struct request *blk_mq_alloc_request(struct request_queue *q, int rw, + gfp_t gfp, bool reserved) { struct request *rq; if (blk_mq_queue_enter(q)) return NULL; - rq = blk_mq_alloc_request_pinned(q, rw, gfp, false); + rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved); blk_mq_put_ctx(rq->mq_ctx); return rq; } @@ -1327,6 +1328,15 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_reg *reg, reg->queue_depth = BLK_MQ_MAX_DEPTH; } + /* + * Set aside a tag for flush requests. It will only be used while + * another flush request is in progress but outside the driver. + * + * TODO: only allocate if flushes are supported + */ + reg->queue_depth++; + reg->reserved_tags++; + if (reg->queue_depth < (reg->reserved_tags + BLK_MQ_TAG_MIN)) return ERR_PTR(-EINVAL); -- cgit v1.2.3-18-g5258