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 9B8CF1DEFF4; Wed, 6 Nov 2024 12:08:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730894903; cv=none; b=CxjvUuc1yjovch0U3KT/wv5JRUennADUdzZXghfrhfeyAtfSHyvuM58Lj5EwSozUadcCYT+t/kHGGweuhC/fksnjKsZbYFA2Ja8U010AHtIXUt5dOQNwkFlJx/s3VU9wkvJRexmhKsNLVken/0H/iT4EeB1ptoiQhQGozrfJf6s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730894903; c=relaxed/simple; bh=TtYmwPGlOJBSBjzSkAOqOyjjrYsBETpHLm7ThcvPYZg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KrHuEDbAzeIJxi3GML3y415YIVbmxxidGysKavqSisOaa2JzMC2bsfzJRZthb+VT9M1gEdZVku6dwcZ3cVFftFwbB9320HQ0QAtAbkHONbSHdhZ6UmwHvQBfQqZ6C4QIRdP3h7T78m5tEQX+fMHax3MbC1WZUkyBfDBHYdBRcWI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JmvPv5Qs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JmvPv5Qs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 230A4C4CECD; Wed, 6 Nov 2024 12:08:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730894903; bh=TtYmwPGlOJBSBjzSkAOqOyjjrYsBETpHLm7ThcvPYZg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JmvPv5QsgX0+7grj94dcH35FUWbrzha78cErdjYaBUWi0DXhMst/L3uhcWukKCcVd oWNVEFaWnYyhaHl1ttOycp1/l8WK3JwLTeXgTHeKj6+8vEO1Bi5yAJ96UZTHNtI1n9 wjVCM5Uox+wFovAYeRbMURx6QCM05D9ktHTRCjNA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Jens Axboe , Sasha Levin Subject: [PATCH 4.19 038/350] block, bfq: choose the last bfqq from merge chain in bfq_setup_cooperator() Date: Wed, 6 Nov 2024 12:59:26 +0100 Message-ID: <20241106120321.826385595@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120320.865793091@linuxfoundation.org> References: <20241106120320.865793091@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yu Kuai [ Upstream commit 0e456dba86c7f9a19792204a044835f1ca2c8dbb ] Consider the following merge chain: Process 1 Process 2 Process 3 Process 4 (BIC1) (BIC2) (BIC3) (BIC4) Λ | | | \--------------\ \-------------\ \-------------\| V V V bfqq1--------->bfqq2---------->bfqq3----------->bfqq4 IO from Process 1 will get bfqf2 from BIC1 first, then bfq_setup_cooperator() will found bfqq2 already merged to bfqq3 and then handle this IO from bfqq3. However, the merge chain can be much deeper and bfqq3 can be merged to other bfqq as well. Fix this problem by iterating to the last bfqq in bfq_setup_cooperator(). Fixes: 36eca8948323 ("block, bfq: add Early Queue Merge (EQM)") Signed-off-by: Yu Kuai Link: https://lore.kernel.org/r/20240902130329.3787024-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-iosched.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 1479e8d6fede2..3ed6584496f34 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2226,8 +2226,12 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_queue *in_service_bfqq, *new_bfqq; /* if a merge has already been setup, then proceed with that first */ - if (bfqq->new_bfqq) - return bfqq->new_bfqq; + new_bfqq = bfqq->new_bfqq; + if (new_bfqq) { + while (new_bfqq->new_bfqq) + new_bfqq = new_bfqq->new_bfqq; + return new_bfqq; + } /* * Prevent bfqq from being merged if it has been created too -- 2.43.0