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block: generic request_queue reference counting

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Allow pmem, and other synchronous/bio-based block drivers, to fallback
on a per-cpu reference count managed by the core for tracking queue
live/dead state.

The existing per-cpu reference count for the blk_mq case is promoted to
be used in all block i/o scenarios.  This involves initializing it by
default, waiting for it to drop to zero at exit, and holding a live
reference over the invocation of q->make_request_fn() in
generic_make_request().  The blk_mq code continues to take its own
reference per blk_mq request and retains the ability to freeze the
queue, but the check that the queue is frozen is moved to
generic_make_request().

This fixes crash signatures like the following:

 BUG: unable to handle kernel paging request at ffff880140000000
 [..]
 Call Trace:
  [<ffffffff8145e8bf>] ? copy_user_handle_tail+0x5f/0x70
  [<ffffffffa004e1e0>] pmem_do_bvec.isra.11+0x70/0xf0 [nd_pmem]
  [<ffffffffa004e331>] pmem_make_request+0xd1/0x200 [nd_pmem]
  [<ffffffff811c3162>] ? mempool_alloc+0x72/0x1a0
  [<ffffffff8141f8b6>] generic_make_request+0xd6/0x110
  [<ffffffff8141f966>] submit_bio+0x76/0x170
  [<ffffffff81286dff>] submit_bh_wbc+0x12f/0x160
  [<ffffffff81286e62>] submit_bh+0x12/0x20
  [<ffffffff813395bd>] jbd2_write_superblock+0x8d/0x170
  [<ffffffff8133974d>] jbd2_mark_journal_empty+0x5d/0x90
  [<ffffffff813399cb>] jbd2_journal_destroy+0x24b/0x270
  [<ffffffff810bc4ca>] ? put_pwq_unlocked+0x2a/0x30
  [<ffffffff810bc6f5>] ? destroy_workqueue+0x225/0x250
  [<ffffffff81303494>] ext4_put_super+0x64/0x360
  [<ffffffff8124ab1a>] generic_shutdown_super+0x6a/0xf0

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Dan Williams 2015-10-21 13:20:12 -04:00 committed by Jens Axboe
parent 4cfc766e07
commit 3ef28e83ab
7 changed files with 102 additions and 75 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
block/blk-core.c
View File

@ -554,13 +554,10 @@ void blk_cleanup_queue(struct request_queue *q)
* Drain all requests queued before DYING marking. Set DEAD flag to
* prevent that q->request_fn() gets invoked after draining finished.
*/
if (q->mq_ops) {
blk_mq_freeze_queue(q);
spin_lock_irq(lock);
} else {
blk_freeze_queue(q);
spin_lock_irq(lock);
if (!q->mq_ops)
__blk_drain_queue(q, true);
}
queue_flag_set(QUEUE_FLAG_DEAD, q);
spin_unlock_irq(lock);
@ -570,6 +567,7 @@ void blk_cleanup_queue(struct request_queue *q)
if (q->mq_ops)
blk_mq_free_queue(q);
percpu_ref_exit(&q->q_usage_counter);
spin_lock_irq(lock);
if (q->queue_lock != &q->__queue_lock)
@ -629,6 +627,40 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
}
EXPORT_SYMBOL(blk_alloc_queue);
int blk_queue_enter(struct request_queue *q, gfp_t gfp)
{
while (true) {
int ret;
if (percpu_ref_tryget_live(&q->q_usage_counter))
return 0;
if (!(gfp & __GFP_WAIT))
return -EBUSY;
ret = wait_event_interruptible(q->mq_freeze_wq,
!atomic_read(&q->mq_freeze_depth) ||
blk_queue_dying(q));
if (blk_queue_dying(q))
return -ENODEV;
if (ret)
return ret;
}
}
void blk_queue_exit(struct request_queue *q)
{
percpu_ref_put(&q->q_usage_counter);
}
static void blk_queue_usage_counter_release(struct percpu_ref *ref)
{
struct request_queue *q =
container_of(ref, struct request_queue, q_usage_counter);
wake_up_all(&q->mq_freeze_wq);
}
struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
{
struct request_queue *q;
@ -690,11 +722,22 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
init_waitqueue_head(&q->mq_freeze_wq);
if (blkcg_init_queue(q))
/*
* Init percpu_ref in atomic mode so that it's faster to shutdown.
* See blk_register_queue() for details.
*/
if (percpu_ref_init(&q->q_usage_counter,
blk_queue_usage_counter_release,
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
goto fail_bdi;
if (blkcg_init_queue(q))
goto fail_ref;
return q;
fail_ref:
percpu_ref_exit(&q->q_usage_counter);
fail_bdi:
bdi_destroy(&q->backing_dev_info);
fail_split:
@ -1966,9 +2009,19 @@ void generic_make_request(struct bio *bio)
do {
struct request_queue *q = bdev_get_queue(bio->bi_bdev);
if (likely(blk_queue_enter(q, __GFP_WAIT) == 0)) {
q->make_request_fn(q, bio);
blk_queue_exit(q);
bio = bio_list_pop(current->bio_list);
} else {
struct bio *bio_next = bio_list_pop(current->bio_list);
bio_io_error(bio);
bio = bio_next;
}
} while (bio);
current->bio_list = NULL; /* deactivate */
}

6
block/blk-mq-sysfs.c
View File

@ -413,12 +413,6 @@ static void blk_mq_sysfs_init(struct request_queue *q)
kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
}
/* see blk_register_queue() */
void blk_mq_finish_init(struct request_queue *q)
{
percpu_ref_switch_to_percpu(&q->mq_usage_counter);
}
int blk_mq_register_disk(struct gendisk *disk)
{
struct device *dev = disk_to_dev(disk);

80
block/blk-mq.c
View File

@ -78,47 +78,13 @@ static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
}
static int blk_mq_queue_enter(struct request_queue *q, gfp_t gfp)
{
while (true) {
int ret;
if (percpu_ref_tryget_live(&q->mq_usage_counter))
return 0;
if (!(gfp & __GFP_WAIT))
return -EBUSY;
ret = wait_event_interruptible(q->mq_freeze_wq,
!atomic_read(&q->mq_freeze_depth) ||
blk_queue_dying(q));
if (blk_queue_dying(q))
return -ENODEV;
if (ret)
return ret;
}
}
static void blk_mq_queue_exit(struct request_queue *q)
{
percpu_ref_put(&q->mq_usage_counter);
}
static void blk_mq_usage_counter_release(struct percpu_ref *ref)
{
struct request_queue *q =
container_of(ref, struct request_queue, mq_usage_counter);
wake_up_all(&q->mq_freeze_wq);
}
void blk_mq_freeze_queue_start(struct request_queue *q)
{
int freeze_depth;
freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
if (freeze_depth == 1) {
percpu_ref_kill(&q->mq_usage_counter);
percpu_ref_kill(&q->q_usage_counter);
blk_mq_run_hw_queues(q, false);
}
}
@ -126,18 +92,34 @@ EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start);
static void blk_mq_freeze_queue_wait(struct request_queue *q)
{
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
}
/*
* Guarantee no request is in use, so we can change any data structure of
* the queue afterward.
*/
void blk_mq_freeze_queue(struct request_queue *q)
void blk_freeze_queue(struct request_queue *q)
{
/*
* In the !blk_mq case we are only calling this to kill the
* q_usage_counter, otherwise this increases the freeze depth
* and waits for it to return to zero. For this reason there is
* no blk_unfreeze_queue(), and blk_freeze_queue() is not
* exported to drivers as the only user for unfreeze is blk_mq.
*/
blk_mq_freeze_queue_start(q);
blk_mq_freeze_queue_wait(q);
}
void blk_mq_freeze_queue(struct request_queue *q)
{
/*
* ...just an alias to keep freeze and unfreeze actions balanced
* in the blk_mq_* namespace
*/
blk_freeze_queue(q);
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
void blk_mq_unfreeze_queue(struct request_queue *q)
@ -147,7 +129,7 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
WARN_ON_ONCE(freeze_depth < 0);
if (!freeze_depth) {
percpu_ref_reinit(&q->mq_usage_counter);
percpu_ref_reinit(&q->q_usage_counter);
wake_up_all(&q->mq_freeze_wq);
}
}
@ -256,7 +238,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
struct blk_mq_alloc_data alloc_data;
int ret;
ret = blk_mq_queue_enter(q, gfp);
ret = blk_queue_enter(q, gfp);
if (ret)
return ERR_PTR(ret);
@ -279,7 +261,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
}
blk_mq_put_ctx(ctx);
if (!rq) {
blk_mq_queue_exit(q);
blk_queue_exit(q);
return ERR_PTR(-EWOULDBLOCK);
}
return rq;
@ -298,7 +280,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
blk_mq_put_tag(hctx, tag, &ctx->last_tag);
blk_mq_queue_exit(q);
blk_queue_exit(q);
}
void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
@ -1177,11 +1159,7 @@ static struct request *blk_mq_map_request(struct request_queue *q,
int rw = bio_data_dir(bio);
struct blk_mq_alloc_data alloc_data;
if (unlikely(blk_mq_queue_enter(q, GFP_KERNEL))) {
bio_io_error(bio);
return NULL;
}
blk_queue_enter_live(q);
ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
@ -2000,14 +1978,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
hctxs[i]->queue_num = i;
}
/*
* Init percpu_ref in atomic mode so that it's faster to shutdown.
* See blk_register_queue() for details.
*/
if (percpu_ref_init(&q->mq_usage_counter, blk_mq_usage_counter_release,
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
goto err_hctxs;
setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q);
blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
@ -2088,8 +2058,6 @@ void blk_mq_free_queue(struct request_queue *q)
blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
blk_mq_free_hw_queues(q, set);
percpu_ref_exit(&q->mq_usage_counter);
}
/* Basically redo blk_mq_init_queue with queue frozen */

3
block/blk-sysfs.c
View File

@ -599,9 +599,8 @@ int blk_register_queue(struct gendisk *disk)
*/
if (!blk_queue_init_done(q)) {
queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
percpu_ref_switch_to_percpu(&q->q_usage_counter);
blk_queue_bypass_end(q);
if (q->mq_ops)
blk_mq_finish_init(q);
}
ret = blk_trace_init_sysfs(dev);

14
block/blk.h
View File

@ -72,6 +72,20 @@ void blk_dequeue_request(struct request *rq);
void __blk_queue_free_tags(struct request_queue *q);
bool __blk_end_bidi_request(struct request *rq, int error,
unsigned int nr_bytes, unsigned int bidi_bytes);
int blk_queue_enter(struct request_queue *q, gfp_t gfp);
void blk_queue_exit(struct request_queue *q);
void blk_freeze_queue(struct request_queue *q);
static inline void blk_queue_enter_live(struct request_queue *q)
{
/*
* Given that running in generic_make_request() context
* guarantees that a live reference against q_usage_counter has
* been established, further references under that same context
* need not check that the queue has been frozen (marked dead).
*/
percpu_ref_get(&q->q_usage_counter);
}
void blk_rq_timed_out_timer(unsigned long data);
unsigned long blk_rq_timeout(unsigned long timeout);

1
include/linux/blk-mq.h
View File

@ -166,7 +166,6 @@ enum {
struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *);
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
struct request_queue *q);
void blk_mq_finish_init(struct request_queue *q);
int blk_mq_register_disk(struct gendisk *);
void blk_mq_unregister_disk(struct gendisk *);

2
include/linux/blkdev.h
View File

@ -450,7 +450,7 @@ struct request_queue {
#endif
struct rcu_head rcu_head;
wait_queue_head_t mq_freeze_wq;
struct percpu_ref mq_usage_counter;
struct percpu_ref q_usage_counter;
struct list_head all_q_node;
struct blk_mq_tag_set *tag_set;