blk-mq: bitmap tag: fix races on shared ::wake_index fields
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>
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 1aab39f..6deb130 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -43,9 +43,16 @@
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 @@
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 @@
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 @@
{
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 @@
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);
}
}
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 98696a6..6206ed1 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -24,7 +24,7 @@
unsigned int map_nr;
struct blk_align_bitmap *map;
- unsigned int wake_index;
+ atomic_t wake_index;
struct bt_wait_state *bs;
};
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a002cf1..eb726b9 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -42,7 +42,7 @@
unsigned int nr_ctx;
struct blk_mq_ctx **ctxs;
- unsigned int wait_index;
+ atomic_t wait_index;
struct blk_mq_tags *tags;