2007-07-27 05:16:14

by Yan Zheng

Subject: [BUG?] "ext4_ext_put_in_cache" uses __u32 to receive physical block number.

Hi, all

I think I found a bug in ext4/extents.c, "ext4_ext_put_in_cache" uses
"__u32" to receive physical block number. "ext4_ext_put_in_cache" is
used in "ext4_ext_get_blocks", it sets ext4 inode's extent cache
according most recently tree lookup (higher 16 bits of saved physical
block number are always zero). when serving a mapping request,
"ext4_ext_get_blocks" first check whether the logical block is in
inode's extent cache. if the logical block is in the cache and the
cached region isn't a gap, "ext4_ext_get_blocks" gets physical block
number by using cached region's physical block number and offset in
the cached region. as described above, "ext4_ext_get_blocks" may
return wrong result when there are physical block numbers bigger than
0xffffffff.

Regards

YZ

2007-07-27 15:39:49

by Mingming Cao

Subject: Re: [BUG?] "ext4_ext_put_in_cache" uses __u32 to receive physical block number.

On Fri, 2007-07-27 at 13:16 +0800, Yan Zheng wrote:
> Hi, all
>
> I think I found a bug in ext4/extents.c, "ext4_ext_put_in_cache" uses
> "__u32" to receive physical block number. "ext4_ext_put_in_cache" is
> used in "ext4_ext_get_blocks", it sets ext4 inode's extent cache
> according most recently tree lookup (higher 16 bits of saved physical
> block number are always zero). when serving a mapping request,
> "ext4_ext_get_blocks" first check whether the logical block is in
> inode's extent cache. if the logical block is in the cache and the
> cached region isn't a gap, "ext4_ext_get_blocks" gets physical block
> number by using cached region's physical block number and offset in
> the cached region. as described above, "ext4_ext_get_blocks" may
> return wrong result when there are physical block numbers bigger than
> 0xffffffff.
>
> Regards
>
> YZ

You are right. Thanks for reporting this!

Signed-off-by: Mingming Cao <[email protected]>

Index: linux-2.6.22/fs/ext4/extents.c
===================================================================
--- linux-2.6.22.orig/fs/ext4/extents.c 2007-07-27 08:31:02.000000000 -0700
+++ linux-2.6.22/fs/ext4/extents.c 2007-07-27 08:31:48.000000000 -0700
@@ -1544,7 +1544,7 @@ int ext4_ext_walk_space(struct inode *in

static void
ext4_ext_put_in_cache(struct inode *inode, __u32 block,
- __u32 len, __u32 start, int type)
+ __u32 len, ext4_fsblk_t start, int type)
{
struct ext4_ext_cache *cex;
BUG_ON(len == 0);