From: tytso@mit.edu Subject: Re: [PATCH 2.6.32.7] ext4: number of blocks for fiemap Date: Mon, 15 Feb 2010 14:50:01 -0500 Message-ID: <20100215195001.GN5337@thunk.org> References: <1257360161.22057.16.camel@michlmayr> <372739E0-41AD-4DEC-9187-1396BE5894BD@sun.com> <1257371050.13852.28.camel@michlmayr> <4B701793.9010005@canonical.com> <1266000136.4310.36.camel@michlmayr> <4D0CB743-94B6-49AB-B838-BCDD2EC8C3ED@sun.com> <1266016801.27587.13.camel@michlmayr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , ext4 development , "linux-kernel@vger.kernel.org Mailinglist" , 474597@bugs.launchpad.net To: Leonard Michlmayr Return-path: Received: from thunk.org ([69.25.196.29]:46657 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756287Ab0BOTuG (ORCPT ); Mon, 15 Feb 2010 14:50:06 -0500 Content-Disposition: inline In-Reply-To: <1266016801.27587.13.camel@michlmayr> Sender: linux-ext4-owner@vger.kernel.org List-ID: Sorry for the delay in attending to this patch. This is what I've added to the ext4 patch queue. - Ted commit 7f9aeb212e41ea20f61061d51ad11ee2449853f1 Author: Theodore Ts'o Date: Mon Feb 15 14:48:32 2010 -0500 ext4: correctly calculate number of blocks for fiemap ext4_fiemap() rounds the length of the requested range down to blocksize, which is is not the true number of blocks that cover the requested region. This problem is especially impressive if the user requests only the first byte of a file: not a single extent will be reported. We fix this by calculating the last block of the region and then subtract to find the number of blocks in the extents. Signed-off-by: Leonard Michlmayr Signed-off-by: "Theodore Ts'o" diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index bd80891..bc9860f 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3768,7 +3768,6 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, __u64 start, __u64 len) { ext4_lblk_t start_blk; - ext4_lblk_t len_blks; int error = 0; /* fallback to generic here if not in extents fmt */ @@ -3782,8 +3781,11 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) { error = ext4_xattr_fiemap(inode, fieinfo); } else { + ext4_lblk_t last_blk, len_blks; + start_blk = start >> inode->i_sb->s_blocksize_bits; - len_blks = len >> inode->i_sb->s_blocksize_bits; + last_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits; + len_blks = last_blk - start_blk + 1; /* * Walk the extent tree gathering extent information.