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[198.137.202.133]) by mx.google.com with ESMTPS id a8si11556473pgw.380.2019.02.26.05.02.34 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 26 Feb 2019 05:02:34 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 198.137.202.133 as permitted sender) client-ip=198.137.202.133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b="Dm/Icpah"; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 198.137.202.133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=iCmFmWiV3xb5AOVJB0XEU/x7knedJSI2kLqY2YUO43c=; b=Dm/IcpahO0ZOhqdZYsO+RF9de HcWTIk0ykKJwiCQ7ClRXTt33MZpvZJoBiDPktX7H6P3wZ9EX7UPTWEa50nDi8oiuAI/yvXUXWqYBO 3fjWdTdySwFhkitqGJ/aJDr2WJQ58BtyHaJqEydY95E1cKqnddoPiM9ZhuzewlzohU1M5pwa9Bt5B G44IAyEGHk28DfhE/IfTiTb/YDRUCfaxPfITn/rb+RVNijE8duubfXeLZNga198lOoywJnnYxLWvK bVa//J7t3actOLmik7JsKmn2/VnIZ6f6eA+X40kB8DVFx+415kByOpzltDAoIp69vbtdt3RGrlTQf 0Qlpp3tXA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gycNS-0005tY-Bt; Tue, 26 Feb 2019 13:02:30 +0000 Date: Tue, 26 Feb 2019 05:02:30 -0800 From: Matthew Wilcox To: Ming Lei Cc: Ming Lei , Vlastimil Babka , Dave Chinner , "Darrick J . Wong" , "open list:XFS FILESYSTEM" , Jens Axboe , Vitaly Kuznetsov , Dave Chinner , Christoph Hellwig , Alexander Duyck , Aaron Lu , Christopher Lameter , Linux FS Devel , linux-mm , linux-block , Pekka Enberg , David Rientjes , Joonsoo Kim Subject: Re: [PATCH] xfs: allocate sector sized IO buffer via page_frag_alloc Message-ID: <20190226130230.GD11592@bombadil.infradead.org> References: <20190225202630.GG23020@dastard> <20190226022249.GA17747@ming.t460p> <20190226030214.GI23020@dastard> <20190226032737.GA11592@bombadil.infradead.org> <20190226045826.GJ23020@dastard> <20190226093302.GA24879@ming.t460p> <20190226121209.GC11592@bombadil.infradead.org> <20190226123545.GA6163@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190226123545.GA6163@ming.t460p> User-Agent: Mutt/1.9.2 (2017-12-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 26, 2019 at 08:35:46PM +0800, Ming Lei wrote: > On Tue, Feb 26, 2019 at 04:12:09AM -0800, Matthew Wilcox wrote: > > On Tue, Feb 26, 2019 at 07:12:49PM +0800, Ming Lei wrote: > > > The buffer needs to be device block size aligned for dio, and now the block > > > size can be 512, 1024, 2048 and 4096. > > > > Why does the block size make a difference? This requirement is due to > > some storage devices having shoddy DMA controllers. Are you saying there > > are devices which can't even do 512-byte aligned I/O? > > Direct IO requires that, see do_blockdev_direct_IO(). > > This issue can be triggered when running xfs over loop/dio. We could > fallback to buffered IO under this situation, but not sure it is the > only case. Wait, we're imposing a ridiculous amount of complexity on XFS for no reason at all? We should just change this to 512-byte alignment. Tying it to the blocksize of the device never made any sense.