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 <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index 06636f3..853f927 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -693,11 +693,20 @@
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 @@
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 9143e85..66e2b69 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -130,20 +130,26 @@
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 @@
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 @@
}
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 @@
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 @@
* 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 @@
* 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 @@
/*
* @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 @@
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 14c8f35..a59b056 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -194,27 +194,9 @@
}
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 @@
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 @@
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 @@
/*
* 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 @@
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 @@
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 @@
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 @@
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 @@
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 f29b645..ed0035c 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -28,6 +28,7 @@
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 8095c4a..7500f87 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -549,6 +549,8 @@
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 468be242d..18ba8a6 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -36,15 +36,12 @@
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_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 0375654..b2d25ec 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -101,7 +101,7 @@
};
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 @@
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;