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[213.95.11.211]) by mx.google.com with ESMTPS id o198-v6si11434221wmg.131.2018.05.22.01.25.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 May 2018 01:25:49 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id BBF4F68D0F; Tue, 22 May 2018 10:31:03 +0200 (CEST) Date: Tue, 22 May 2018 10:31:03 +0200 From: Christoph Hellwig To: "Darrick J. Wong" Cc: Christoph Hellwig , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 16/34] iomap: add initial support for writes without buffer heads Message-ID: <20180522083103.GA10079@lst.de> References: <20180518164830.1552-1-hch@lst.de> <20180518164830.1552-17-hch@lst.de> <20180521232700.GB14384@magnolia> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180521232700.GB14384@magnolia> User-Agent: Mutt/1.5.17 (2007-11-01) 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: X-Virus-Scanned: ClamAV using ClamSMTP The fix should be as simple as this: diff --git a/fs/iomap.c b/fs/iomap.c index 357711e50cfa..212c3c21e51c 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -342,19 +342,19 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, loff_t block_end = (pos + len + block_size - 1) & ~(block_size - 1); unsigned poff = block_start & (PAGE_SIZE - 1); unsigned plen = min_t(loff_t, PAGE_SIZE - poff, block_end - block_start); + unsigned from = pos & (PAGE_SIZE - 1); + unsigned to = from + len; int status; WARN_ON_ONCE(i_blocksize(inode) < PAGE_SIZE); if (PageUptodate(page)) return 0; + if (poff >= from && poff + len <= to) + return 0; if (iomap_block_needs_zeroing(inode, block_start, iomap)) { - unsigned from = pos & (PAGE_SIZE - 1), to = from + len; - unsigned pend = poff + plen; - - if (poff < from || pend > to) - zero_user_segments(page, poff, from, to, pend); + zero_user_segments(page, poff, from, to, poff + len); } else { status = iomap_read_page_sync(inode, block_start, page, poff, plen, iomap);