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blk-mq: bitmap tag: fix races on shared ::wake_index fields

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Fix racy updates of shared blk_mq_bitmap_tags::wake_index
and blk_mq_hw_ctx::wake_index fields.

Cc: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Alexander Gordeev 2014-06-17 22:12:35 -07:00 committed by Jens Axboe
parent 736ed4de76
commit 8537b12034
3 changed files with 23 additions and 13 deletions
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32
block/blk-mq-tag.c
View File

@ -43,9 +43,16 @@ bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
return bt_has_free_tags(&tags->bitmap_tags);
}
static inline void bt_index_inc(unsigned int *index)
static inline int bt_index_inc(int index)
{
*index = (*index + 1) & (BT_WAIT_QUEUES - 1);
return (index + 1) & (BT_WAIT_QUEUES - 1);
}
static inline void bt_index_atomic_inc(atomic_t *index)
{
int old = atomic_read(index);
int new = bt_index_inc(old);
atomic_cmpxchg(index, old, new);
}
/*
@ -69,14 +76,14 @@ static void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags)
int i, wake_index;
bt = &tags->bitmap_tags;
wake_index = bt->wake_index;
wake_index = atomic_read(&bt->wake_index);
for (i = 0; i < BT_WAIT_QUEUES; i++) {
struct bt_wait_state *bs = &bt->bs[wake_index];
if (waitqueue_active(&bs->wait))
wake_up(&bs->wait);
bt_index_inc(&wake_index);
wake_index = bt_index_inc(wake_index);
}
}
@ -212,12 +219,14 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
struct blk_mq_hw_ctx *hctx)
{
struct bt_wait_state *bs;
int wait_index;
if (!hctx)
return &bt->bs[0];
bs = &bt->bs[hctx->wait_index];
bt_index_inc(&hctx->wait_index);
wait_index = atomic_read(&hctx->wait_index);
bs = &bt->bs[wait_index];
bt_index_atomic_inc(&hctx->wait_index);
return bs;
}
@ -313,18 +322,19 @@ static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
{
int i, wake_index;
wake_index = bt->wake_index;
wake_index = atomic_read(&bt->wake_index);
for (i = 0; i < BT_WAIT_QUEUES; i++) {
struct bt_wait_state *bs = &bt->bs[wake_index];
if (waitqueue_active(&bs->wait)) {
if (wake_index != bt->wake_index)
bt->wake_index = wake_index;
int o = atomic_read(&bt->wake_index);
if (wake_index != o)
atomic_cmpxchg(&bt->wake_index, o, wake_index);
return bs;
}
bt_index_inc(&wake_index);
wake_index = bt_index_inc(wake_index);
}
return NULL;
@ -344,7 +354,7 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
bs = bt_wake_ptr(bt);
if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
atomic_set(&bs->wait_cnt, bt->wake_cnt);
bt_index_inc(&bt->wake_index);
bt_index_atomic_inc(&bt->wake_index);
wake_up(&bs->wait);
}
}

2
block/blk-mq-tag.h
View File

@ -24,7 +24,7 @@ struct blk_mq_bitmap_tags {
unsigned int map_nr;
struct blk_align_bitmap *map;
unsigned int wake_index;
atomic_t wake_index;
struct bt_wait_state *bs;
};

2
include/linux/blk-mq.h
View File

@ -42,7 +42,7 @@ struct blk_mq_hw_ctx {
unsigned int nr_ctx;
struct blk_mq_ctx **ctxs;
unsigned int wait_index;
atomic_t wait_index;
struct blk_mq_tags *tags;