2016-02-21 17:37:46

by Eryu Guan

Subject: [PATCH] ext4: iterate over buffer heads correctly in move_extent_per_page()

In commit bcff24887d00 ("ext4: don't read blocks from disk after extents
being swapped") bh is not updated correctly in the for loop and wrong
data has been written to disk. generic/324 catches this on sub-page
block size ext4.

Fixes: bcff24887d00 ("ext4: don't read blocks from disk after extentsbeing swapped")
Signed-off-by: Eryu Guan <[email protected]>
---

Not sure why I didn't notice generic/324 failure in the first place, it fails
every time for me with 4.5-rc5 kernel. Sorry about that!

I tested this patch with 1k/2k/4k block size ext4 with all defrag related tests
in xfstests (ext4/301 ext4/302 ext4/303 ext4/304 ext4/307 ext4/308 generic/324)
and results showed no regression. Test with the reproducer in commit
bcff24887d00 also passed.

fs/ext4/move_extent.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index e032a04..4098acc 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -390,6 +390,7 @@ data_copy:
*err = ext4_get_block(orig_inode, orig_blk_offset + i, bh, 0);
if (*err < 0)
break;
+ bh = bh->b_this_page;
}
if (!*err)
*err = block_commit_write(pagep[0], from, from + replaced_size);
--
2.5.0

2016-02-21 23:39:48

by Theodore Ts'o

Subject: Re: [PATCH] ext4: iterate over buffer heads correctly in move_extent_per_page()

On Sun, Feb 21, 2016 at 11:57:29PM +0800, Eryu Guan wrote:
> In commit bcff24887d00 ("ext4: don't read blocks from disk after extents
> being swapped") bh is not updated correctly in the for loop and wrong
> data has been written to disk. generic/324 catches this on sub-page
> block size ext4.
>
> Fixes: bcff24887d00 ("ext4: don't read blocks from disk after extentsbeing swapped")
> Signed-off-by: Eryu Guan <[email protected]>

Thanks, applied.

- Ted