On Sat, May 19, 2018 at 03:44:06PM +0800, Ming Lei wrote: > When the allocation process is scheduled back and the mapped hw queue is > changed, do one extra wake up on orignal queue for compensating wake up > miss, so other allocations on the orignal queue won't be starved. > > This patch fixes one request allocation hang issue, which can be > triggered easily in case of very low nr_request. > > Cc: <[email protected]> > Cc: Omar Sandoval <[email protected]> > Signed-off-by: Ming Lei <[email protected]> > --- > > V2: > fix build failure > > block/blk-mq-tag.c | 13 +++++++++++++ > include/linux/sbitmap.h | 7 +++++++ > lib/sbitmap.c | 6 ++++++ > 3 files changed, 26 insertions(+) > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > index 336dde07b230..77607f89d205 100644 > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -134,6 +134,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data > *data) > ws = bt_wait_ptr(bt, data->hctx); > drop_ctx = data->ctx == NULL; > do { > + struct sbitmap_queue *bt_orig; > + > /* > * We're out of tags on this hardware queue, kick any > * pending IO submits before going to sleep waiting for > @@ -159,6 +161,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data > *data) > if (data->ctx) > blk_mq_put_ctx(data->ctx); > > + bt_orig = bt; > io_schedule(); > > data->ctx = blk_mq_get_ctx(data->q); > @@ -170,6 +173,16 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data > *data) > bt = &tags->bitmap_tags; > > finish_wait(&ws->wait, &wait); > + > + /* > + * If destination hw queue is changed, wake up original > + * queue one extra time for compensating the wake up > + * miss, so other allocations on original queue won't > + * be starved. > + */ > + if (bt != bt_orig) > + sbitmap_queue_wake_up(bt_orig); > + > ws = bt_wait_ptr(bt, data->hctx); > } while (1); > > diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h > index 841585f6e5f2..b23f50355281 100644 > --- a/include/linux/sbitmap.h > +++ b/include/linux/sbitmap.h > @@ -484,6 +484,13 @@ static inline struct sbq_wait_state *sbq_wait_ptr(struct > sbitmap_queue *sbq, > void sbitmap_queue_wake_all(struct sbitmap_queue *sbq); > > /** > + * sbitmap_wake_up() - Do a regular wake up compensation if the queue > + * allocated from is changed after scheduling back. > + * @sbq: Bitmap queue to wake up. > + */ > +void sbitmap_queue_wake_up(struct sbitmap_queue *sbq); > + > +/** > * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct > * seq_file. > * @sbq: Bitmap queue to show. > diff --git a/lib/sbitmap.c b/lib/sbitmap.c > index e6a9c06ec70c..c6ae4206bcb1 100644 > --- a/lib/sbitmap.c > +++ b/lib/sbitmap.c > @@ -466,6 +466,12 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) > } > } > > +void sbitmap_queue_wake_up(struct sbitmap_queue *sbq) > +{ > + sbq_wake_up(sbq); > +} > +EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
There's no reason to wrap an internal helper with a function taking the same arguments, just rename sbq_wake_up() and export it.
