This is a note to let you know that I've just added the patch titled
blk-mq: Avoid that __bt_get_word() wraps multiple times
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-mq-avoid-that-__bt_get_word-wraps-multiple-times.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9e98e9d7cf6e9d2ec1cce45e8d5ccaf3f9b386f3 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <[email protected]>
Date: Tue, 9 Dec 2014 16:58:11 +0100
Subject: blk-mq: Avoid that __bt_get_word() wraps multiple times
From: Bart Van Assche <[email protected]>
commit 9e98e9d7cf6e9d2ec1cce45e8d5ccaf3f9b386f3 upstream.
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 <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Robert Elliott <[email protected]>
Cc: Ming Lei <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
block/blk-mq-tag.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -137,6 +137,7 @@ static inline bool hctx_may_queue(struct
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;
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.18/blk-mq-fix-a-use-after-free.patch
queue-3.18/blk-mq-avoid-that-__bt_get_word-wraps-multiple-times.patch
queue-3.18/blk-mq-fix-a-race-between-bt_clear_tag-and-bt_get.patch
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