From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo2-f3.google.com (mail-oo2-f3.google.com [74.125.231.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A49E540B0ED for ; Thu, 30 Jul 2026 11:07:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.231.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785409641; cv=none; b=ughtX+13L+LSCYiZyQiSgMODbwByoEiPtIn+xVPBdsMz+pBWfJGNW3vY+IN9cXHr/KgAWHDEIdylkrgOOBR/yFeajXT4N0QLtaefglRWknG0B2gCl0G/+GOacPlxmvl6dm1K1mp5PQfew7YXIBubvYFP3R/ttW6rSHObsMF5NHw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785409641; c=relaxed/simple; bh=irWaHmZAGIRRdUHsCyazMaPbnaFydrHJHEBjT64HdHQ=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=VHYKqquF4HBRWXjvubhQR569nR5awvgjYaufZ84jiLV3aFz/0EGUdIGl+V4eFkJsHA7q/z+10HHery5hdzDMUoAdNmOLQcAsdrjHpD3E5hutTBHimR70A98RthtTuuyNbwW9O0gjdN9DGJWUeMe22qwCTkIWy3P96IlKtfvodiw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20251104.gappssmtp.com header.i=@kernel-dk.20251104.gappssmtp.com header.b=vOUPABo+; arc=none smtp.client-ip=74.125.231.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20251104.gappssmtp.com header.i=@kernel-dk.20251104.gappssmtp.com header.b="vOUPABo+" Received: by mail-oo2-f3.google.com with SMTP id 006d021491bc7-6a374f73eaeso282713eaf.1 for ; Thu, 30 Jul 2026 04:07:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20251104.gappssmtp.com; s=20251104; t=1785409637; x=1786014437; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:to:subject:user-agent:mime-version:date :message-id:from:to:cc:subject:date:message-id:reply-to:content-type; bh=6ykrmNqt47vR07SUEYkAcFeKnyGvZk3O/7dA2MPCpeI=; b=vOUPABo+Tbpig3J6theCbbpF6oJJ3wM26l+pB6XClYfp5iT0TeZvB5X3GlYSkYG9dN 4dQwoeQU2ZvFE6BAYiakyRDNPd4u2R8CkvG1/j9WFDONwmkOiaaTCFGxdMGD4/+ORjhk J7CZbH3njhq1ZILrPd+8t69mgTIzmi5vyWZYR2krWFtS/85KOBlFWvLshvVv//QhEFS2 SupnWf2ESH2pWRhhfOymGyPVTgwCYFCel/PgUntd2ePHZf5FXwvv4jw2EsDvEbMeX4n/ 1OuyHY/pk0vQqZe9VD4QpiZWYQEc6mA09hpS70DzSPw/+cwiLqwE3UhPxHSK3WzT5e9Z b/Gg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785409637; x=1786014437; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:to:subject:user-agent:mime-version:date :message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=6ykrmNqt47vR07SUEYkAcFeKnyGvZk3O/7dA2MPCpeI=; b=gPaxtzB0rgJyWzXdiEjvmO79iZbGlYkHyCoiPEk8UwJB8Eqhfu7HMXy6WIXakGv+cU 9F/U/L9tcFDSbAmBFxQXvKZN9tyQpYCTsIH9HP+lircAiwabaqPSkG1OHAuZwY2a2ofB bIBVQ1bxdPZQghNlAgkCn0NIlHbtZ6NykApXce9rpghdaplAOufYfwwz++I+dXv8StIE fFCit9jcFzhXp4CH/1YSd5hToS0A3n0cqvJoLHNz9wg+Ok/3Nv/elNfu1DPgNES8+SfW 2tXBZDodIbV/sqg6/TCQE7JP2rU5eH7LtgMU6B/4GkFpo4D+TvLid0i2mtnzKU9JI9gf FJ6w== X-Forwarded-Encrypted: i=1; AHgh+RoasMIiZfqKcH9iylRZdCuzwl6MGopEs8nvygjM54srpgezjs4G2o8aOJSr9cg9b4aCnz9RONw+ezxP7c8=@vger.kernel.org X-Gm-Message-State: AOJu0YxnRLuTgQq2in6EgByca00lVFETIjgpfM/K5+zOa+ljQkHK/wG2 BwPOZ2WQZryuBG9YfWnipzOnmdz3UJalkPQMDyC0W5caDYaKL1g+8CkM63Pct2w7W2OxMS9GMzv RQzxRosOsxM+t X-Gm-Gg: AR+sD105FzTNIAeAVH45Szvf6RgGl1J7nka7Jc/dkLNxYoF/z3HESGVglvidynqYeZP PkqD/0Il6hlXI9mqZTPHJDGsqJJewnuFqb0wITN+MA1vkAgl5ZQJRFSn5PvLtgu7geWtBXmsnLo L6slvIOHMfDAjG4TfPesB1oYDo/8BgXEFbptDM/dj1Jq9IoWtF/sQRbWVtPoEeffCNE9zndrilm oQ6zn1+u9M5IxgP7vZ6ZCBoJrAKjf+Ah+8iJAwU6aedID+/fGJn2gE0hl2uRo15rtz/OsNV4a6T Bnisj/yaSrQDmQuw51kcrVRvLlFPjw4+7lVoTFV+C1Gh0c3r7hA3I9WfpWDwPCOGSPkPJXnguzR uO5OfQueuFpYJk6FACih9x8Z8es8YXFxdyfMPACbvm4IR2qJe8zoXm68Wcmbh0whP0rSAdVkcQd fJ6+jlQBtb6tJATH1VBP3m3R6zy7pAh2CcB3/qhq6B8Ah2ywbSat6vRjthYSS1eCZo9pnoxA/rL 20RWmIVGWj4XLtyoppnJXgcgsZNXh1jehOqtIXgf17dnLQ= X-Received: by 2002:a05:6820:c3da:20b0:6ac:c1b4:1a0c with SMTP id 006d021491bc7-6acc1b4206fmr512948eaf.61.1785409637549; Thu, 30 Jul 2026 04:07:17 -0700 (PDT) Received: from [192.168.1.150] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6acbc23238dsm1295940eaf.2.2026.07.30.04.07.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Jul 2026 04:07:16 -0700 (PDT) Message-ID: <86d67b99-0bb5-4132-b412-9bb68ee4ca8c@kernel.dk> Date: Thu, 30 Jul 2026 05:07:15 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] md: remove REQ_NOWAIT support To: yukuai@fygo.io, Abd-Alrhman Masalkhi , song@kernel.org, magiclinan@didiglobal.com, xiao@kernel.org, vverma@digitalocean.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260628142737.1051059-1-abd.masalkhi@gmail.com> <07b0887a-e546-4d2f-b261-1fe7adb1d6e0@fygo.io> Content-Language: en-US From: Jens Axboe In-Reply-To: <07b0887a-e546-4d2f-b261-1fe7adb1d6e0@fygo.io> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/30/26 4:50 AM, yu kuai wrote: > Hi, > > ? 2026/6/28 22:27, Abd-Alrhman Masalkhi ??: >> REQ_NOWAIT support in md is fundamentally incomplete. While reads can >> avoid some blocking paths, write requests can still encounter cases >> where one mirror succeeds while another returns -EAGAIN. At that point >> md cannot distinguish queue pressure from a real device failure, so it >> can neither record a bad block nor safely retry the write without >> REQ_NOWAIT, leaving mirrors with divergent data. >> >> Rather than continue advertising REQ_NOWAIT support that cannot be >> implemented correctly, remove it from md and its raid personalities. >> This simplifies the waiting paths and avoids exposing incorrect >> non-blocking semantics. >> >> Fixes: bf2c411bb1cf ("md: raid456 add nowait support") >> Fixes: c9aa889b035f ("md: raid10 add nowait support") >> Fixes: 5aa705039c4f ("md: raid1 add nowait support") >> Fixes: f51d46d0e7cb ("md: add support for REQ_NOWAIT") >> Suggested-by: Yu Kuai >> Signed-off-by: Abd-Alrhman Masalkhi >> --- >> drivers/md/md-bitmap.c | 9 +--- >> drivers/md/md-bitmap.h | 2 +- >> drivers/md/md-llbitmap.c | 10 +---- >> drivers/md/md.c | 15 ++----- >> drivers/md/raid1-10.c | 8 ++-- >> drivers/md/raid1.c | 91 +++++++++------------------------------- >> drivers/md/raid10.c | 80 +++++++++-------------------------- >> drivers/md/raid5.c | 13 ------ >> 8 files changed, 51 insertions(+), 177 deletions(-) > > Applied to md-7.3 with a few changes, please check: > > md: remove REQ_NOWAIT support from raid1/10/456 - > kernel/git/mdraid/linux.git - song's fork of linux.git > > - rebase raid1/raid10 with latest code; > - keep nowait for raid0/linear; > - keep nowait for md_handle_request, as raid0/linear will need it; What's the plan for making REQ_NOWAIT _actually_ work with md? Just yanking it wholesale is a massive performance problem, and it will regress workloads. Has any time been spent on making this more solid? -- Jens Axboe