Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754397Ab0FKGDa (ORCPT ); Fri, 11 Jun 2010 02:03:30 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:31024 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751412Ab0FKGD3 (ORCPT ); Fri, 11 Jun 2010 02:03:29 -0400 From: Tao Ma To: xfs@oss.sgi.com Cc: linux-kernel@vger.kernel.org, Tao Ma , Alex Elder , Christoph Hellwig , Dave Chinner Subject: [PATCH] xfs: Make fiemap works with sparse file. Date: Fri, 11 Jun 2010 14:02:15 +0800 Message-Id: <1276236135-12051-1-git-send-email-tao.ma@oracle.com> X-Mailer: git-send-email 1.7.0.4 X-Auth-Type: Internal IP X-Source-IP: acsinet15.oracle.com [141.146.126.227] X-CT-RefId: str=0001.0A090204.4C11D19E.009E:SCFMA922111,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2328 Lines: 57 In xfs_vn_fiemap, we set bvm_count to fi_extent_max + 1 and want to return fi_extent_max extents, but actually it won't work for a sparse file. The reason is that in xfs_getbmap we will calculate holes and set it in 'out', while out is malloced by bmv_count(fi_extent_max+1) which didn't consider holes. So in the worst case, if 'out' vector looks like [hole, extent, hole, extent, hole, ... hole, extent, hole], we will only return half of fi_extent_max extents. So in xfs_vn_fiemap, we should consider this worst case. If the user wants fi_extent_max extents, we need a 'out' with size of 2 *fi_extent_max + 1. Cc: Alex Elder Cc: Christoph Hellwig Cc: Dave Chinner Signed-off-by: Tao Ma --- fs/xfs/linux-2.6/xfs_iops.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_iops.c b/fs/xfs/linux-2.6/xfs_iops.c index 9c8019c..1db92e3 100644 --- a/fs/xfs/linux-2.6/xfs_iops.c +++ b/fs/xfs/linux-2.6/xfs_iops.c @@ -672,9 +672,21 @@ xfs_vn_fiemap( else bm.bmv_length = BTOBB(length); - /* We add one because in getbmap world count includes the header */ + /* + * It is a bit tricky for us to calculate the bmv_count from + * fi_extent_max. + * If we support to return fi_extent_max extents to the user, + * we need at most 2 * fi_extent_max + 1 for bmv_count since + * in xfs_getbmap we will calculate holes while fi_extent_max + * don't have them. So in the worst case, bmv can looks like + * [hole, extent, hole, extent, hole, ... hole, extent, hole]. + * So there will be 2 *fi_extent_max + 1. + * What's more, in getbmap world count have to include the + * header, so we need another bmv. So the total number will + * be 2 * fieinfo->fi_extents_max + 2. + */ bm.bmv_count = !fieinfo->fi_extents_max ? MAXEXTNUM : - fieinfo->fi_extents_max + 1; + 2 * fieinfo->fi_extents_max + 2; bm.bmv_count = min_t(__s32, bm.bmv_count, (PAGE_SIZE * 16 / sizeof(struct getbmapx))); bm.bmv_iflags = BMV_IF_PREALLOC; -- 1.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/