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authorBart Van Assche <bvanassche@acm.org>2014-12-09 16:58:11 +0100
committerJens Axboe <axboe@fb.com>2014-12-09 09:07:14 -0700
commit9e98e9d7cf6e9d2ec1cce45e8d5ccaf3f9b386f3 (patch)
tree9bf1d9e63d5f19088be8a6bfe8e141f6ab887bb4 /block/blk-mq-tag.c
parent45a9c9d909b24c6ad0e28a7946e7486e73010319 (diff)
downloadkernel-9e98e9d7cf6e9d2ec1cce45e8d5ccaf3f9b386f3.tar.gz
blk-mq: Avoid that __bt_get_word() wraps multiple times
If __bt_get_word() is called with last_tag != 0, if the first find_next_zero_bit() fails, if after wrap-around the test_and_set_bit() call fails and find_next_zero_bit() succeeds, if the next test_and_set_bit() call fails and subsequently find_next_zero_bit() does not find a zero bit, then another wrap-around will occur. Avoid this by introducing an additional local variable. Signed-off-by: Bart Van Assche <bvanassche@acm.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Robert Elliott <elliott@hp.com> Cc: Ming Lei <ming.lei@canonical.com> Cc: Alexander Gordeev <agordeev@redhat.com> Cc: <stable@vger.kernel.org> # v3.13+ Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq-tag.c')
-rw-r--r--block/blk-mq-tag.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index bab4bff15f42..0f5e22a7971f 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -137,6 +137,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
{
int tag, org_last_tag, end;
+ bool wrap = last_tag != 0;
org_last_tag = last_tag;
end = bm->depth;
@@ -148,8 +149,9 @@ restart:
* We started with an offset, start from 0 to
* exhaust the map.
*/
- if (org_last_tag && last_tag) {
- end = last_tag;
+ if (wrap) {
+ wrap = false;
+ end = org_last_tag;
last_tag = 0;
goto restart;
}