block: defer timeouts to a workqueue

BugLink: http://bugs.launchpad.net/bugs/1597908
Timer context is not very useful for drivers to perform any meaningful abort
action from.  So instead of calling the driver from this useless context
defer it to a workqueue as soon as possible.

Note that while a delayed_work item would seem the right thing here I didn't
dare to use it due to the magic in blk_add_timer that pokes deep into timer
internals.  But maybe this encourages Tejun to add a sensible API for that to
the workqueue API and we'll all be fine in the end :)

Contains a major update from Keith Bush:

"This patch removes synchronizing the timeout work so that the timer can
 start a freeze on its own queue. The timer enters the queue, so timer
 context can only start a freeze, but not wait for frozen."

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 287922eb0b186e2a5bf54fdd04b734c25c90035c)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 3fe1f99624f488b8da09b45c28dc8dbdbe1b732f..81bd8b1bddfa2e0143c0d56147880b573c81042c 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -680,6 +680,13 @@ static void blk_queue_usage_counter_release(struct percpu_ref *ref)
        wake_up_all(&q->mq_freeze_wq);
 }
 
+static void blk_rq_timed_out_timer(unsigned long data)
+{
+       struct request_queue *q = (struct request_queue *)data;
+
+       kblockd_schedule_work(&q->timeout_work);
+}
+
 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 {
        struct request_queue *q;
@@ -841,6 +848,7 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
        if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
                goto fail;
 
+       INIT_WORK(&q->timeout_work, blk_timeout_work);
        q->request_fn           = rfn;
        q->prep_rq_fn           = NULL;
        q->unprep_rq_fn         = NULL;

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3d24978b53d381ce6d544f09bb8c57ad891f5ec7..4069a0fa9174fa21a27e0ddbd285848f4ec9c5a8 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -617,15 +617,19 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
        }
 }
 
-static void blk_mq_rq_timer(unsigned long priv)
+static void blk_mq_timeout_work(struct work_struct *work)
 {
-       struct request_queue *q = (struct request_queue *)priv;
+       struct request_queue *q =
+               container_of(work, struct request_queue, timeout_work);
        struct blk_mq_timeout_data data = {
                .next           = 0,
                .next_set       = 0,
        };
        int i;
 
+       if (blk_queue_enter(q, true))
+               return;
+
        blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
 
        if (data.next_set) {
@@ -640,6 +644,7 @@ static void blk_mq_rq_timer(unsigned long priv)
                                blk_mq_tag_idle(hctx);
                }
        }
+       blk_queue_exit(q);
 }
 
 /*
@@ -2017,7 +2022,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
                hctxs[i]->queue_num = i;
        }
 
-       setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q);
+       INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
        blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
 
        q->nr_queues = nr_cpu_ids;

diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index aa40aa93381b661b73d5aa0f531e247e148c56a0..7c176f669b35bce53a28a83c610a83768c429622 100644 (file)
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -127,13 +127,16 @@ static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout
        }
 }
 
-void blk_rq_timed_out_timer(unsigned long data)
+void blk_timeout_work(struct work_struct *work)
 {
-       struct request_queue *q = (struct request_queue *) data;
+       struct request_queue *q =
+               container_of(work, struct request_queue, timeout_work);
        unsigned long flags, next = 0;
        struct request *rq, *tmp;
        int next_set = 0;
 
+       if (blk_queue_enter(q, true))
+               return;
        spin_lock_irqsave(q->queue_lock, flags);
 
        list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
@@ -143,6 +146,7 @@ void blk_rq_timed_out_timer(unsigned long data)
                mod_timer(&q->timeout, round_jiffies_up(next));
 
        spin_unlock_irqrestore(q->queue_lock, flags);
+       blk_queue_exit(q);
 }
 
 /**

diff --git a/block/blk.h b/block/blk.h
index c43926d3d74d0578216d1a699b1dfefff2a899df..70e4aee9cdcb6ead5974dce6a5abf454344b5b24 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -93,7 +93,7 @@ static inline void blk_flush_integrity(void)
 }
 #endif
 
-void blk_rq_timed_out_timer(unsigned long data);
+void blk_timeout_work(struct work_struct *work);
 unsigned long blk_rq_timeout(unsigned long timeout);
 void blk_add_timer(struct request *req);
 void blk_delete_timer(struct request *);

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 42f4bcf6061ddf08da1a74aff77f5da7db429a1a..f28a95a06c081f87c856b0c6d74338737508874a 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -408,6 +408,7 @@ struct request_queue {
 
        unsigned int            rq_timeout;
        struct timer_list       timeout;
+       struct work_struct      timeout_work;
        struct list_head        timeout_list;
 
        struct list_head        icq_list;