From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Bart Van Assche , Christoph Hellwig , Robert Elliott , Ming Lei , Alexander Gordeev , Jens Axboe Subject: [PATCH 3.18 048/150] blk-mq: Avoid that __bt_get_word() wraps multiple times Date: Tue, 13 Jan 2015 23:21:59 -0800 Message-Id: <20150114072058.052335987@linuxfoundation.org> In-Reply-To: <20150114072055.842408181@linuxfoundation.org> References: <20150114072055.842408181@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bart Van Assche 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 Cc: Christoph Hellwig Cc: Robert Elliott Cc: Ming Lei Cc: Alexander Gordeev Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- 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; }