[3.16.y-ckt stable] Patch "blk-mq: Avoid that __bt_get_word() wraps multiple times" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Wed Jan 7 10:30:28 UTC 2015
This is a note to let you know that I have just added a patch titled
blk-mq: Avoid that __bt_get_word() wraps multiple times
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt4.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 652f8983ce76fd819dcfdea52db39f9eac3ed4cc Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche at acm.org>
Date: Tue, 9 Dec 2014 16:58:11 +0100
Subject: blk-mq: Avoid that __bt_get_word() wraps multiple times
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 <bvanassche at acm.org>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Robert Elliott <elliott at hp.com>
Cc: Ming Lei <ming.lei at canonical.com>
Cc: Alexander Gordeev <agordeev at redhat.com>
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
block/blk-mq-tag.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 74a4168ea34e..a1bc33974fc4 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;
}
--
2.1.4
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