From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2ED47BA32 for ; Tue, 7 Mar 2023 17:12:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75502C433EF; Tue, 7 Mar 2023 17:12:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678209144; bh=aBsVWss/WL+JUp7zxGhwBjJIR+37KsExODhWAvvd6Z8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UlyWX4dD91Dpc2Kc5mfwGqcA+ybxndc/eaLdWkHlIDhQo24ShPf4igtAseLQ72Nx3 xCQuvRvepFga9DaVPwWJcFdeldJh+ZB0AxzABU7YmCqD7iAYTFeVnr8xP2u1s0AXC8 XeTJu8LkaHJqdUigxFviYQxhxs2KWCY/mOguas+0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Kemeng Shi , Jens Axboe , Sasha Levin Subject: [PATCH 6.2 0095/1001] sbitmap: remove redundant check in __sbitmap_queue_get_batch Date: Tue, 7 Mar 2023 17:47:47 +0100 Message-Id: <20230307170026.290120382@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230307170022.094103862@linuxfoundation.org> References: <20230307170022.094103862@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Kemeng Shi [ Upstream commit 903e86f3a64d9573352bbab2f211fdbbaa5772b7 ] Commit fbb564a557809 ("lib/sbitmap: Fix invalid loop in __sbitmap_queue_get_batch()") mentioned that "Checking free bits when setting the target bits. Otherwise, it may reuse the busying bits." This commit add check to make sure all masked bits in word before cmpxchg is zero. Then the existing check after cmpxchg to check any zero bit is existing in masked bits in word is redundant. Actually, old value of word before cmpxchg is stored in val and we will filter out busy bits in val by "(get_mask & ~val)" after cmpxchg. So we will not reuse busy bits methioned in commit fbb564a557809 ("lib/sbitmap: Fix invalid loop in __sbitmap_queue_get_batch()"). Revert new-added check to remove redundant check. Fixes: fbb564a55780 ("lib/sbitmap: Fix invalid loop in __sbitmap_queue_get_batch()") Reviewed-by: Jan Kara Signed-off-by: Kemeng Shi Link: https://lore.kernel.org/r/20230116205059.3821738-3-shikemeng@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- lib/sbitmap.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 1fcede228fa25..2281fbb49d5c6 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -521,11 +521,9 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags, get_mask = ((1UL << nr_tags) - 1) << nr; val = READ_ONCE(map->word); - do { - if ((val & ~get_mask) != val) - goto next; - } while (!atomic_long_try_cmpxchg(ptr, &val, - get_mask | val)); + while (!atomic_long_try_cmpxchg(ptr, &val, + get_mask | val)) + ; get_mask = (get_mask & ~val) >> nr; if (get_mask) { *offset = nr + (index << sb->shift); -- 2.39.2