summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorBart Van Assche <bart.vanassche@sandisk.com>2016-11-02 10:09:51 -0600
committerJens Axboe <axboe@fb.com>2016-11-02 11:17:24 -0600
commit641b49d661caebf5f702ae694b527b71508733ea (patch)
tree871df14894af953b8486575a2803f038c8f33c4a
parent684c774b56bd6fbdf6878b1581be3bc45b4a6606 (diff)
blk-mq: Introduce blk_mq_quiesce_queue()
blk_mq_quiesce_queue() waits until ongoing .queue_rq() invocations have finished. This function does *not* wait until all outstanding requests have finished (this means invocation of request.end_io()). The algorithm used by blk_mq_quiesce_queue() is as follows: * Hold either an RCU read lock or an SRCU read lock around .queue_rq() calls. The former is used if .queue_rq() does not block and the latter if .queue_rq() may block. * blk_mq_quiesce_queue() first calls blk_mq_stop_hw_queues() followed by synchronize_srcu() or synchronize_rcu(). The latter call waits for .queue_rq() invocations that started before blk_mq_quiesce_queue() was called. * The blk_mq_hctx_stopped() calls that control whether or not .queue_rq() will be called are called with the (S)RCU read lock held. This is necessary to avoid race conditions against blk_mq_quiesce_queue(). Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Ming Lei <tom.leiming@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/Kconfig1
-rw-r--r--block/blk-mq.c71
-rw-r--r--include/linux/blk-mq.h3
-rw-r--r--include/linux/blkdev.h1
4 files changed, 69 insertions, 7 deletions
diff --git a/block/Kconfig b/block/Kconfig
index 6b0ad08f0677..3a024440a669 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -5,6 +5,7 @@ menuconfig BLOCK
bool "Enable the block layer" if EXPERT
default y
select SBITMAP
+ select SRCU
help
Provide block layer support for the kernel.
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a461823644fb..3dc323543293 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -115,6 +115,33 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
+/**
+ * blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished
+ * @q: request queue.
+ *
+ * Note: this function does not prevent that the struct request end_io()
+ * callback function is invoked. Additionally, it is not prevented that
+ * new queue_rq() calls occur unless the queue has been stopped first.
+ */
+void blk_mq_quiesce_queue(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+ bool rcu = false;
+
+ blk_mq_stop_hw_queues(q);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (hctx->flags & BLK_MQ_F_BLOCKING)
+ synchronize_srcu(&hctx->queue_rq_srcu);
+ else
+ rcu = true;
+ }
+ if (rcu)
+ synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
+
void blk_mq_wake_waiters(struct request_queue *q)
{
struct blk_mq_hw_ctx *hctx;
@@ -766,7 +793,7 @@ static inline unsigned int queued_to_index(unsigned int queued)
* of IO. In particular, we'd like FIFO behaviour on handling existing
* items on the hctx->dispatch list. Ignore that for now.
*/
-static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
+static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
{
struct request_queue *q = hctx->queue;
struct request *rq;
@@ -778,9 +805,6 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
if (unlikely(blk_mq_hctx_stopped(hctx)))
return;
- WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
- cpu_online(hctx->next_cpu));
-
hctx->run++;
/*
@@ -871,6 +895,24 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
}
}
+static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
+{
+ int srcu_idx;
+
+ WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
+ cpu_online(hctx->next_cpu));
+
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+ rcu_read_lock();
+ blk_mq_process_rq_list(hctx);
+ rcu_read_unlock();
+ } else {
+ srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu);
+ blk_mq_process_rq_list(hctx);
+ srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx);
+ }
+}
+
/*
* It'd be great if the workqueue API had a way to pass
* in a mask and had some smarts for more clever placement.
@@ -1268,7 +1310,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
struct blk_mq_alloc_data data;
struct request *rq;
- unsigned int request_count = 0;
+ unsigned int request_count = 0, srcu_idx;
struct blk_plug *plug;
struct request *same_queue_rq = NULL;
blk_qc_t cookie;
@@ -1311,7 +1353,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
blk_mq_bio_to_request(rq, bio);
/*
- * We do limited pluging. If the bio can be merged, do that.
+ * We do limited plugging. If the bio can be merged, do that.
* Otherwise the existing request in the plug list will be
* issued. So the plug list will have one request at most
*/
@@ -1331,7 +1373,16 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
blk_mq_put_ctx(data.ctx);
if (!old_rq)
goto done;
- blk_mq_try_issue_directly(data.hctx, old_rq, &cookie);
+
+ if (!(data.hctx->flags & BLK_MQ_F_BLOCKING)) {
+ rcu_read_lock();
+ blk_mq_try_issue_directly(data.hctx, old_rq, &cookie);
+ rcu_read_unlock();
+ } else {
+ srcu_idx = srcu_read_lock(&data.hctx->queue_rq_srcu);
+ blk_mq_try_issue_directly(data.hctx, old_rq, &cookie);
+ srcu_read_unlock(&data.hctx->queue_rq_srcu, srcu_idx);
+ }
goto done;
}
@@ -1610,6 +1661,9 @@ static void blk_mq_exit_hctx(struct request_queue *q,
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
+ if (hctx->flags & BLK_MQ_F_BLOCKING)
+ cleanup_srcu_struct(&hctx->queue_rq_srcu);
+
blk_mq_remove_cpuhp(hctx);
blk_free_flush_queue(hctx->fq);
sbitmap_free(&hctx->ctx_map);
@@ -1690,6 +1744,9 @@ static int blk_mq_init_hctx(struct request_queue *q,
flush_start_tag + hctx_idx, node))
goto free_fq;
+ if (hctx->flags & BLK_MQ_F_BLOCKING)
+ init_srcu_struct(&hctx->queue_rq_srcu);
+
return 0;
free_fq:
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a85a20f80aaa..ed20ac74c62a 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -3,6 +3,7 @@
#include <linux/blkdev.h>
#include <linux/sbitmap.h>
+#include <linux/srcu.h>
struct blk_mq_tags;
struct blk_flush_queue;
@@ -35,6 +36,8 @@ struct blk_mq_hw_ctx {
struct blk_mq_tags *tags;
+ struct srcu_struct queue_rq_srcu;
+
unsigned long queued;
unsigned long run;
#define BLK_MQ_MAX_DISPATCH_ORDER 7
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8396da2bb698..13d893a69b46 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -918,6 +918,7 @@ extern void __blk_run_queue(struct request_queue *q);
extern void __blk_run_queue_uncond(struct request_queue *q);
extern void blk_run_queue(struct request_queue *);
extern void blk_run_queue_async(struct request_queue *q);
+extern void blk_mq_quiesce_queue(struct request_queue *q);
extern int blk_rq_map_user(struct request_queue *, struct request *,
struct rq_map_data *, void __user *, unsigned long,
gfp_t);