From patchwork Fri May 21 17:03:37 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josef Bacik X-Patchwork-Id: 101523 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.3/8.14.3) with ESMTP id o4LH8PbM031507 for ; Fri, 21 May 2010 17:08:25 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934469Ab0EURG2 (ORCPT ); Fri, 21 May 2010 13:06:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41618 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934436Ab0EURGZ (ORCPT ); Fri, 21 May 2010 13:06:25 -0400 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o4LH5mK8030522 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 21 May 2010 13:05:48 -0400 Received: from localhost.localdomain (test1244.test.redhat.com [10.10.10.244]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o4LH5lu8001618; Fri, 21 May 2010 13:05:47 -0400 From: Josef Bacik To: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, akpm@linux-foundation.org Subject: [PATCH 1/6] fs: allow short direct-io reads to be completed via buffered IO Date: Fri, 21 May 2010 13:03:37 -0400 Message-Id: <1274461422-18433-1-git-send-email-josef@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.16 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter.kernel.org [140.211.167.41]); Fri, 21 May 2010 17:08:27 +0000 (UTC) diff --git a/mm/filemap.c b/mm/filemap.c index 140ebda..829ac9c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1263,7 +1263,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, { struct file *filp = iocb->ki_filp; ssize_t retval; - unsigned long seg; + unsigned long seg = 0; size_t count; loff_t *ppos = &iocb->ki_pos; @@ -1290,21 +1290,47 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, retval = mapping->a_ops->direct_IO(READ, iocb, iov, pos, nr_segs); } - if (retval > 0) + if (retval > 0) { *ppos = pos + retval; - if (retval) { + count -= retval; + } + + /* + * Btrfs can have a short DIO read if we encounter + * compressed extents, so if there was an error, or if + * we've already read everything we wanted to, or if + * there was a short read because we hit EOF, go ahead + * and return. Otherwise fallthrough to buffered io for + * the rest of the read. + */ + if (retval < 0 || !count || *ppos >= size) { file_accessed(filp); goto out; } } } + count = retval; for (seg = 0; seg < nr_segs; seg++) { read_descriptor_t desc; + loff_t offset = 0; + + /* + * If we did a short DIO read we need to skip the section of the + * iov that we've already read data into. + */ + if (count) { + if (count > iov[seg].iov_len) { + count -= iov[seg].iov_len; + continue; + } + offset = count; + count = 0; + } desc.written = 0; - desc.arg.buf = iov[seg].iov_base; - desc.count = iov[seg].iov_len; + desc.arg.buf = iov[seg].iov_base + offset; + desc.count = iov[seg].iov_len - offset; if (desc.count == 0) continue; desc.error = 0;