From: Eric Sandeen Subject: Re: [PATCH 2.6.32.7] ext4: number of blocks for fiemap Date: Mon, 15 Feb 2010 14:33:03 -0600 Message-ID: <4B79AF7F.2030209@redhat.com> 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> <20100215195001.GN5337@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: tytso@mit.edu, Leonard Michlmayr , Andreas Dilger , ext4 development , "linux-kernel@vger.kernel.org Mailingl Return-path: Received: from mx1.redhat.com ([209.132.183.28]:20582 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756525Ab0BOUdO (ORCPT ); Mon, 15 Feb 2010 15:33:14 -0500 In-Reply-To: <20100215195001.GN5337@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: tytso@mit.edu wrote: > 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 Ted, it looks like perhaps you accidentally reassigned authorship for this patch? -Eric > 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. > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html