linux-ext4 - Re: [BUG?] "ext4_ext_put_in_cache" uses __u32 to receive physical block number.

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Date:	Fri, 27 Jul 2007 08:39:43 -0700
From:	Mingming Cao <cmm@...ibm.com>
To:	Yan Zheng <yanzheng@...n.com>, akpm@...l.org, stable@...nel.org,
	tytso@....edu
Cc:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
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 <cmm@...ibm.com>

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);


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