Re: [PATCH] ext4: fix loss of delalloc extent info in ext4_zero_range()

[Theodore Ts'o <tytso@mit.edu>]

On Fri, Mar 20, 2015 at 07:53:50PM -0400, Eric Whitney wrote:
> In ext4_zero_range(), removing a file's entire block range from the
> extent status tree removes all records of that file's delalloc extents.
> The delalloc accounting code uses this information, and its loss can
> then lead to accounting errors and kernel warnings at writeback time and
> subsequent file system damage.  This is most noticeable on bigalloc
> file systems where code in ext4_ext_map_blocks() handles cases where
> delalloc extents share clusters with a newly allocated extent.
> 
> Because we're not deleting a block range and are correctly updating the
> status of its associated extent, there is no need to remove anything
> from the extent status tree.
> 
> When this patch is combined with an unrelated bug fix for
> ext4_zero_range(), kernel warnings and e2fsck errors reported during
> xfstests runs on bigalloc filesystems are greatly reduced without
> introducing regressions on other xfstests-bld test scenarios.
> 
> Signed-off-by: Eric Whitney <enwlinux@gmail.com>

Applied, thanks.

					- Ted