From 18741986a4b1dc4b1f171634c4191abc3b0fa023 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 10 Feb 2014 09:29:00 -0700 Subject: [PATCH] blk-mq: rework flush sequencing logic Witch to using a preallocated flush_rq for blk-mq similar to what's done with the old request path. This allows us to set up the request properly with a tag from the actually allowed range and ->rq_disk as needed by some drivers. To make life easier we also switch to dynamic allocation of ->flush_rq for the old path. This effectively reverts most of "blk-mq: fix for flush deadlock" and "blk-mq: Don't reserve a tag for flush request" Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-core.c | 15 ++++-- block/blk-flush.c | 105 +++++++++++++++-------------------------- block/blk-mq.c | 54 ++++++++------------- block/blk-mq.h | 1 + block/blk-sysfs.c | 2 + include/linux/blk-mq.h | 5 +- include/linux/blkdev.h | 11 ++--- 7 files changed, 76 insertions(+), 117 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 06636f3ad424..853f92749202 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -693,11 +693,20 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id) if (!uninit_q) return NULL; + uninit_q->flush_rq = kzalloc(sizeof(struct request), GFP_KERNEL); + if (!uninit_q->flush_rq) + goto out_cleanup_queue; + q = blk_init_allocated_queue(uninit_q, rfn, lock); if (!q) - blk_cleanup_queue(uninit_q); - + goto out_free_flush_rq; return q; + +out_free_flush_rq: + kfree(uninit_q->flush_rq); +out_cleanup_queue: + blk_cleanup_queue(uninit_q); + return NULL; } EXPORT_SYMBOL(blk_init_queue_node); @@ -1127,7 +1136,7 @@ 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, false); + return blk_mq_alloc_request(q, rw, gfp_mask); else return blk_old_get_request(q, rw, gfp_mask); } diff --git a/block/blk-flush.c b/block/blk-flush.c index 9143e85226c7..66e2b697f5db 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -130,20 +130,26 @@ static void blk_flush_restore_request(struct request *rq) blk_clear_rq_complete(rq); } -static void mq_flush_data_run(struct work_struct *work) +static void mq_flush_run(struct work_struct *work) { struct request *rq; - rq = container_of(work, struct request, mq_flush_data); + rq = container_of(work, struct request, mq_flush_work); memset(&rq->csd, 0, sizeof(rq->csd)); blk_mq_run_request(rq, true, false); } -static void blk_mq_flush_data_insert(struct request *rq) +static bool blk_flush_queue_rq(struct request *rq) { - INIT_WORK(&rq->mq_flush_data, mq_flush_data_run); - kblockd_schedule_work(rq->q, &rq->mq_flush_data); + if (rq->q->mq_ops) { + INIT_WORK(&rq->mq_flush_work, mq_flush_run); + kblockd_schedule_work(rq->q, &rq->mq_flush_work); + return false; + } else { + list_add_tail(&rq->queuelist, &rq->q->queue_head); + return true; + } } /** @@ -187,12 +193,7 @@ static bool blk_flush_complete_seq(struct request *rq, unsigned int seq, case REQ_FSEQ_DATA: list_move_tail(&rq->flush.list, &q->flush_data_in_flight); - if (q->mq_ops) - blk_mq_flush_data_insert(rq); - else { - list_add(&rq->queuelist, &q->queue_head); - queued = true; - } + queued = blk_flush_queue_rq(rq); break; case REQ_FSEQ_DONE: @@ -216,9 +217,6 @@ static bool blk_flush_complete_seq(struct request *rq, unsigned int seq, } kicked = blk_kick_flush(q); - /* blk_mq_run_flush will run queue */ - if (q->mq_ops) - return queued; return kicked | queued; } @@ -230,10 +228,9 @@ static void flush_end_io(struct request *flush_rq, int error) struct request *rq, *n; unsigned long flags = 0; - if (q->mq_ops) { - blk_mq_free_request(flush_rq); + if (q->mq_ops) spin_lock_irqsave(&q->mq_flush_lock, flags); - } + running = &q->flush_queue[q->flush_running_idx]; BUG_ON(q->flush_pending_idx == q->flush_running_idx); @@ -263,48 +260,14 @@ static void flush_end_io(struct request *flush_rq, int error) * kblockd. */ if (queued || q->flush_queue_delayed) { - if (!q->mq_ops) - blk_run_queue_async(q); - else - /* - * This can be optimized to only run queues with requests - * queued if necessary. - */ - blk_mq_run_queues(q, true); + WARN_ON(q->mq_ops); + blk_run_queue_async(q); } q->flush_queue_delayed = 0; if (q->mq_ops) spin_unlock_irqrestore(&q->mq_flush_lock, flags); } -static void mq_flush_work(struct work_struct *work) -{ - struct request_queue *q; - struct request *rq; - - q = container_of(work, struct request_queue, mq_flush_work); - - rq = blk_mq_alloc_request(q, WRITE_FLUSH|REQ_FLUSH_SEQ, - __GFP_WAIT|GFP_ATOMIC, false); - rq->cmd_type = REQ_TYPE_FS; - rq->end_io = flush_end_io; - - blk_mq_run_request(rq, true, false); -} - -/* - * We can't directly use q->flush_rq, because it doesn't have tag and is not in - * hctx->rqs[]. so we must allocate a new request, since we can't sleep here, - * so offload the work to workqueue. - * - * Note: we assume a flush request finished in any hardware queue will flush - * the whole disk cache. - */ -static void mq_run_flush(struct request_queue *q) -{ - kblockd_schedule_work(q, &q->mq_flush_work); -} - /** * blk_kick_flush - consider issuing flush request * @q: request_queue being kicked @@ -339,19 +302,31 @@ static bool blk_kick_flush(struct request_queue *q) * different from running_idx, which means flush is in flight. */ q->flush_pending_idx ^= 1; + if (q->mq_ops) { - mq_run_flush(q); - return true; + struct blk_mq_ctx *ctx = first_rq->mq_ctx; + struct blk_mq_hw_ctx *hctx = q->mq_ops->map_queue(q, ctx->cpu); + + blk_mq_rq_init(hctx, q->flush_rq); + q->flush_rq->mq_ctx = ctx; + + /* + * Reuse the tag value from the fist waiting request, + * with blk-mq the tag is generated during request + * allocation and drivers can rely on it being inside + * the range they asked for. + */ + q->flush_rq->tag = first_rq->tag; + } else { + blk_rq_init(q, q->flush_rq); } - blk_rq_init(q, &q->flush_rq); - q->flush_rq.cmd_type = REQ_TYPE_FS; - q->flush_rq.cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ; - q->flush_rq.rq_disk = first_rq->rq_disk; - q->flush_rq.end_io = flush_end_io; + q->flush_rq->cmd_type = REQ_TYPE_FS; + q->flush_rq->cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ; + q->flush_rq->rq_disk = first_rq->rq_disk; + q->flush_rq->end_io = flush_end_io; - list_add_tail(&q->flush_rq.queuelist, &q->queue_head); - return true; + return blk_flush_queue_rq(q->flush_rq); } static void flush_data_end_io(struct request *rq, int error) @@ -407,11 +382,8 @@ void blk_insert_flush(struct request *rq) /* * @policy now records what operations need to be done. Adjust * REQ_FLUSH and FUA for the driver. - * We keep REQ_FLUSH for mq to track flush requests. For !FUA, - * we never dispatch the request directly. */ - if (rq->cmd_flags & REQ_FUA) - rq->cmd_flags &= ~REQ_FLUSH; + rq->cmd_flags &= ~REQ_FLUSH; if (!(fflags & REQ_FUA)) rq->cmd_flags &= ~REQ_FUA; @@ -560,5 +532,4 @@ EXPORT_SYMBOL(blkdev_issue_flush); void blk_mq_init_flush(struct request_queue *q) { spin_lock_init(&q->mq_flush_lock); - INIT_WORK(&q->mq_flush_work, mq_flush_work); } diff --git a/block/blk-mq.c b/block/blk-mq.c index 14c8f35946e1..a59b0565e940 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -194,27 +194,9 @@ static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx, } static struct request *__blk_mq_alloc_request(struct blk_mq_hw_ctx *hctx, - gfp_t gfp, bool reserved, - int rw) + gfp_t gfp, bool reserved) { - struct request *req; - bool is_flush = false; - /* - * flush need allocate a request, leave at least one request for - * non-flush IO to avoid deadlock - */ - if ((rw & REQ_FLUSH) && !(rw & REQ_FLUSH_SEQ)) { - if (atomic_inc_return(&hctx->pending_flush) >= - hctx->queue_depth - hctx->reserved_tags - 1) { - atomic_dec(&hctx->pending_flush); - return NULL; - } - is_flush = true; - } - req = blk_mq_alloc_rq(hctx, gfp, reserved); - if (!req && is_flush) - atomic_dec(&hctx->pending_flush); - return req; + return blk_mq_alloc_rq(hctx, gfp, reserved); } static struct request *blk_mq_alloc_request_pinned(struct request_queue *q, @@ -227,7 +209,7 @@ static struct request *blk_mq_alloc_request_pinned(struct request_queue *q, struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); struct blk_mq_hw_ctx *hctx = q->mq_ops->map_queue(q, ctx->cpu); - rq = __blk_mq_alloc_request(hctx, gfp & ~__GFP_WAIT, reserved, rw); + rq = __blk_mq_alloc_request(hctx, gfp & ~__GFP_WAIT, reserved); if (rq) { blk_mq_rq_ctx_init(q, ctx, rq, rw); break; @@ -244,15 +226,14 @@ 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, bool reserved) +struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp) { struct request *rq; if (blk_mq_queue_enter(q)) return NULL; - rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved); + rq = blk_mq_alloc_request_pinned(q, rw, gfp, false); if (rq) blk_mq_put_ctx(rq->mq_ctx); return rq; @@ -276,7 +257,7 @@ 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) +void blk_mq_rq_init(struct blk_mq_hw_ctx *hctx, struct request *rq) { blk_rq_init(hctx->queue, rq); @@ -290,9 +271,6 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, const int tag = rq->tag; struct request_queue *q = rq->q; - if ((rq->cmd_flags & REQ_FLUSH) && !(rq->cmd_flags & REQ_FLUSH_SEQ)) - atomic_dec(&hctx->pending_flush); - blk_mq_rq_init(hctx, rq); blk_mq_put_tag(hctx->tags, tag); @@ -946,14 +924,14 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) hctx = q->mq_ops->map_queue(q, ctx->cpu); trace_block_getrq(q, bio, rw); - rq = __blk_mq_alloc_request(hctx, GFP_ATOMIC, false, bio->bi_rw); + rq = __blk_mq_alloc_request(hctx, GFP_ATOMIC, false); if (likely(rq)) - blk_mq_rq_ctx_init(q, ctx, rq, bio->bi_rw); + blk_mq_rq_ctx_init(q, ctx, rq, rw); else { blk_mq_put_ctx(ctx); trace_block_sleeprq(q, bio, rw); - rq = blk_mq_alloc_request_pinned(q, bio->bi_rw, - __GFP_WAIT|GFP_ATOMIC, false); + rq = blk_mq_alloc_request_pinned(q, rw, __GFP_WAIT|GFP_ATOMIC, + false); ctx = rq->mq_ctx; hctx = q->mq_ops->map_queue(q, ctx->cpu); } @@ -1230,9 +1208,7 @@ static int blk_mq_init_hw_queues(struct request_queue *q, hctx->queue_num = i; hctx->flags = reg->flags; hctx->queue_depth = reg->queue_depth; - hctx->reserved_tags = reg->reserved_tags; hctx->cmd_size = reg->cmd_size; - atomic_set(&hctx->pending_flush, 0); blk_mq_init_cpu_notifier(&hctx->cpu_notifier, blk_mq_hctx_notify, hctx); @@ -1412,9 +1388,14 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_reg *reg, blk_mq_init_flush(q); blk_mq_init_cpu_queues(q, reg->nr_hw_queues); - if (blk_mq_init_hw_queues(q, reg, driver_data)) + q->flush_rq = kzalloc(round_up(sizeof(struct request) + reg->cmd_size, + cache_line_size()), GFP_KERNEL); + if (!q->flush_rq) goto err_hw; + if (blk_mq_init_hw_queues(q, reg, driver_data)) + goto err_flush_rq; + blk_mq_map_swqueue(q); mutex_lock(&all_q_mutex); @@ -1422,6 +1403,9 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_reg *reg, mutex_unlock(&all_q_mutex); return q; + +err_flush_rq: + kfree(q->flush_rq); err_hw: kfree(q->mq_map); err_map: diff --git a/block/blk-mq.h b/block/blk-mq.h index f29b645f0e1c..ed0035cd458e 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -28,6 +28,7 @@ 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_drain_queue(struct request_queue *q); void blk_mq_free_queue(struct request_queue *q); +void blk_mq_rq_init(struct blk_mq_hw_ctx *hctx, struct request *rq); /* * CPU hotplug helpers diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 8095c4a21fc0..7500f876dae4 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -549,6 +549,8 @@ static void blk_release_queue(struct kobject *kobj) if (q->mq_ops) blk_mq_free_queue(q); + kfree(q->flush_rq); + blk_trace_shutdown(q); bdi_destroy(&q->backing_dev_info); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 468be242db90..18ba8a627f46 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -36,15 +36,12 @@ struct blk_mq_hw_ctx { struct list_head page_list; struct blk_mq_tags *tags; - atomic_t pending_flush; - unsigned long queued; unsigned long run; #define BLK_MQ_MAX_DISPATCH_ORDER 10 unsigned long dispatched[BLK_MQ_MAX_DISPATCH_ORDER]; unsigned int queue_depth; - unsigned int reserved_tags; unsigned int numa_node; unsigned int cmd_size; /* per-request extra data */ @@ -129,7 +126,7 @@ void blk_mq_insert_request(struct request_queue *, struct request *, void blk_mq_run_queues(struct request_queue *q, bool async); void blk_mq_free_request(struct request *rq); bool blk_mq_can_queue(struct blk_mq_hw_ctx *); -struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp, bool reserved); +struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp); struct request *blk_mq_alloc_reserved_request(struct request_queue *q, int rw, gfp_t gfp); struct request *blk_mq_rq_from_tag(struct request_queue *q, unsigned int tag); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 0375654adb28..b2d25ecbcbc1 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -101,7 +101,7 @@ struct request { }; union { struct call_single_data csd; - struct work_struct mq_flush_data; + struct work_struct mq_flush_work; }; struct request_queue *q; @@ -451,13 +451,8 @@ struct request_queue { unsigned long flush_pending_since; struct list_head flush_queue[2]; struct list_head flush_data_in_flight; - union { - struct request flush_rq; - struct { - spinlock_t mq_flush_lock; - struct work_struct mq_flush_work; - }; - }; + struct request *flush_rq; + spinlock_t mq_flush_lock; struct mutex sysfs_lock; -- GitLab