From: Leonard Michlmayr <leonard.michlmayr@gmail.com>
To: Andreas Dilger <adilger@sun.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: ext4_fiemap gives 0 extents for files smaller than a block (patch included)
Date: Wed, 04 Nov 2009 19:42:41 +0100 [thread overview]
Message-ID: <1257360161.22057.16.camel@michlmayr> (raw)
[-- Attachment #1: Type: text/plain, Size: 356 bytes --]
Fiemap (ioctl) does not return any extents for small files on ext4.
(fm_start=0, fm_length=filesize)
File affected: fs/ext4/extents.c
I found the reason of the bug: wrong rounding. It will not only affect
small files, but any request that overlaps an extent boundary by less
that blocksize.
The attached patch is against 2.6.32-rc5.
Leonard Michlmayr
[-- Attachment #2: ext4_fiemap_fix.patch --]
[-- Type: text/x-patch, Size: 745 bytes --]
diff -Naur linux-2.6.32-rc5/fs/ext4/extents.c linux-2.6.32-rc5.patched/fs/ext4/extents.c
--- linux-2.6.32-rc5/fs/ext4/extents.c 2009-10-16 02:41:50.000000000 +0200
+++ linux-2.6.32-rc5.patched/fs/ext4/extents.c 2009-11-04 19:35:44.000000000 +0100
@@ -3685,6 +3685,7 @@
__u64 start, __u64 len)
{
ext4_lblk_t start_blk;
+ ext4_lblk_t end_blk;
ext4_lblk_t len_blks;
int error = 0;
@@ -3700,7 +3701,8 @@
error = ext4_xattr_fiemap(inode, fieinfo);
} else {
start_blk = start >> inode->i_sb->s_blocksize_bits;
- len_blks = len >> inode->i_sb->s_blocksize_bits;
+ end_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
+ len_blks = end_blk - start_blk + 1;
/*
* Walk the extent tree gathering extent information.
next reply other threads:[~2009-11-04 18:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-04 18:42 Leonard Michlmayr [this message]
2009-11-04 19:44 ` ext4_fiemap gives 0 extents for files smaller than a block (patch included) Andreas Dilger
2009-11-04 21:44 ` Leonard Michlmayr
2010-02-08 13:54 ` Surbhi Palande
2010-02-12 18:42 ` [PATCH 2.6.32.7] ext4: number of blocks for fiemap Leonard Michlmayr
2010-02-12 21:49 ` Andreas Dilger
2010-02-12 23:20 ` Leonard Michlmayr
2010-02-15 19:50 ` tytso
2010-02-15 20:33 ` Eric Sandeen
2010-02-15 22:01 ` tytso
2010-01-25 19:04 ` ext4_fiemap gives 0 extents for files smaller than a block (patch included) Leonard Michlmayr
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