The patch below does not apply to the 3.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 9e98e9d7cf6e9d2ec1cce45e8d5ccaf3f9b386f3 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@xxxxxxx>
Date: Tue, 9 Dec 2014 16:58:11 +0100
Subject: [PATCH] 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@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Robert Elliott <elliott@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.13+
Signed-off-by: Jens Axboe <axboe@xxxxxx>
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;
}
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