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authorMing Lei <ming.lei@redhat.com>2021-05-11 23:22:35 +0800
committerJens Axboe <axboe@kernel.dk>2021-05-24 06:47:22 -0600
commitbd63141d585bef14f4caf111f6d0e27fe2300ec6 (patch)
tree18c509a0a1fb0b90746396b360a5b1e5b46bae37 /block
parent2e315dc07df009c3e29d6926871f62a30cfae394 (diff)
blk-mq: clear stale request in tags->rq[] before freeing one request pool
refcount_inc_not_zero() in bt_tags_iter() still may read one freed request. Fix the issue by the following approach: 1) hold a per-tags spinlock when reading ->rqs[tag] and calling refcount_inc_not_zero in bt_tags_iter() 2) clearing stale request referred via ->rqs[tag] before freeing request pool, the per-tags spinlock is held for clearing stale ->rq[tag] So after we cleared stale requests, bt_tags_iter() won't observe freed request any more, also the clearing will wait for pending request reference. The idea of clearing ->rqs[] is borrowed from John Garry's previous patch and one recent David's patch. Tested-by: John Garry <john.garry@huawei.com> Reviewed-by: David Jeffery <djeffery@redhat.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20210511152236.763464-4-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq-tag.c9
-rw-r--r--block/blk-mq-tag.h6
-rw-r--r--block/blk-mq.c46
3 files changed, 54 insertions, 7 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 544edf2c56a5..1671dae43030 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -202,10 +202,14 @@ struct bt_iter_data {
static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
unsigned int bitnr)
{
- struct request *rq = tags->rqs[bitnr];
+ struct request *rq;
+ unsigned long flags;
+ spin_lock_irqsave(&tags->lock, flags);
+ rq = tags->rqs[bitnr];
if (!rq || !refcount_inc_not_zero(&rq->ref))
- return NULL;
+ rq = NULL;
+ spin_unlock_irqrestore(&tags->lock, flags);
return rq;
}
@@ -538,6 +542,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags;
+ spin_lock_init(&tags->lock);
if (blk_mq_is_sbitmap_shared(flags))
return tags;
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index 7d3e6b333a4a..f887988e5ef6 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -20,6 +20,12 @@ struct blk_mq_tags {
struct request **rqs;
struct request **static_rqs;
struct list_head page_list;
+
+ /*
+ * used to clear request reference in rqs[] before freeing one
+ * request pool
+ */
+ spinlock_t lock;
};
extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index debfa5cd8025..dd371f321d35 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2307,6 +2307,45 @@ queue_exit:
return BLK_QC_T_NONE;
}
+static size_t order_to_size(unsigned int order)
+{
+ return (size_t)PAGE_SIZE << order;
+}
+
+/* called before freeing request pool in @tags */
+static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
+ struct blk_mq_tags *tags, unsigned int hctx_idx)
+{
+ struct blk_mq_tags *drv_tags = set->tags[hctx_idx];
+ struct page *page;
+ unsigned long flags;
+
+ list_for_each_entry(page, &tags->page_list, lru) {
+ unsigned long start = (unsigned long)page_address(page);
+ unsigned long end = start + order_to_size(page->private);
+ int i;
+
+ for (i = 0; i < set->queue_depth; i++) {
+ struct request *rq = drv_tags->rqs[i];
+ unsigned long rq_addr = (unsigned long)rq;
+
+ if (rq_addr >= start && rq_addr < end) {
+ WARN_ON_ONCE(refcount_read(&rq->ref) != 0);
+ cmpxchg(&drv_tags->rqs[i], rq, NULL);
+ }
+ }
+ }
+
+ /*
+ * Wait until all pending iteration is done.
+ *
+ * Request reference is cleared and it is guaranteed to be observed
+ * after the ->lock is released.
+ */
+ spin_lock_irqsave(&drv_tags->lock, flags);
+ spin_unlock_irqrestore(&drv_tags->lock, flags);
+}
+
void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
unsigned int hctx_idx)
{
@@ -2325,6 +2364,8 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
}
}
+ blk_mq_clear_rq_mapping(set, tags, hctx_idx);
+
while (!list_empty(&tags->page_list)) {
page = list_first_entry(&tags->page_list, struct page, lru);
list_del_init(&page->lru);
@@ -2384,11 +2425,6 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
return tags;
}
-static size_t order_to_size(unsigned int order)
-{
- return (size_t)PAGE_SIZE << order;
-}
-
static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
unsigned int hctx_idx, int node)
{