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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id c7si9931453pgn.277.2019.04.26.05.45.55 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 26 Apr 2019 05:45:55 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of batv+69eb5840461690eae8c6+5724+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=AZhuFqvb; spf=pass (google.com: best guess record for domain of batv+69eb5840461690eae8c6+5724+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+69eb5840461690eae8c6+5724+infradead.org+hch@bombadil.srs.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=akHd8JqiMAzxrz2WCE0z9Z8wSwIAjNmdXhzSk4evgGw=; b=AZhuFqvb56ZemhjhPqPx8RzlB DHLTZNxiXAREhfS6hcQN84QTKvH+1PpWmT3ZWfsXF+elp2AQmuYMqGB2t3FEbi0ghPRncdVSagaUg smuSONJ+ayLRN+gwNnSaVtu/M7pIk1lzVenHes52Rp0bV1GYl1e5fx3YIjo4uYepzFcszxh3NyQuI 6BJ994ZTbSsB/zVBP8yoQ04uSFpxPPUImZBAYzRQMwjI3NfjMEhuXJrp1MHliAIYRWty+euxnpKua qZKTJVagxc4Kmqtc601X8scFFP7/0W6OCj1Src9tP32GYwPDBknVCaZ7Va2LSJJEgOXC8jpQR+kyy s6+S28swg==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hK0Ej-0007PV-L6; Fri, 26 Apr 2019 12:45:53 +0000 Date: Fri, 26 Apr 2019 05:45:53 -0700 From: Christoph Hellwig To: Dave Chinner Cc: Jerome Glisse , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [LSF/MM TOPIC] Direct block mapping through fs for device Message-ID: <20190426124553.GB12339@infradead.org> References: <20190426013814.GB3350@redhat.com> <20190426062816.GG1454@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426062816.GG1454@dread.disaster.area> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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 Fri, Apr 26, 2019 at 04:28:16PM +1000, Dave Chinner wrote: > i.e. go look at how xfs_pnfs.c works to hand out block mappings to > remote pNFS clients so they can directly access the underlying > storage. Basically, anyone wanting to map blocks needs a file layout > lease and then to manage the filesystem state over that range via > these methods in the struct export_operations: > > int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset); > int (*map_blocks)(struct inode *inode, loff_t offset, > u64 len, struct iomap *iomap, > bool write, u32 *device_generation); > int (*commit_blocks)(struct inode *inode, struct iomap *iomaps, > int nr_iomaps, struct iattr *iattr); Nipick: get_uuid isn't needed for the least itself, it just works around the fact that the original pNFS/block protocol is braindead. The pNFS/SCSI prototocol already switches to a device UUID, and other users that work locally shouldn't need it either.