On 09/30/2015 06:28 AM, Chandan Rajendra wrote:
The following issue was observed when running generic/095 test on
subpagesize-blocksize patchset.
Assume that we are trying to write a dirty page that is mapping file offset
range [159744, 163839].
writepage_delalloc()
find_lock_delalloc_range(*start = 159744, *end = 0)
find_delalloc_range()
Returns range [X, Y] where (X > 163839)
lock_delalloc_pages()
One of the pages in range [X, Y] has dirty flag cleared;
Loop once more restricting the delalloc range to span only
PAGE_CACHE_SIZE bytes;
find_delalloc_range()
Returns range [356352, 360447];
lock_delalloc_pages()
The page [356352, 360447] has dirty flag cleared;
Returns with *start = 159744 and *end = 0;
*start = *end + 1;
find_lock_delalloc_range(*start = 1, *end = 0)
Finds and returns delalloc range [1, 12288];
cow_file_range()
Clears delalloc range [1, 12288]
Create ordered extent for range [1, 12288]
The ordered extent thus created above breaks the rule that extents have to be
aligned to the filesystem's block size.
In cases where lock_delalloc_pages() fails (either due to PG_dirty flag being
cleared or the page no longer being a member of the inode's page cache), this
patch sets and returns the delalloc range that was found by
find_delalloc_range().
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josef Bacik <jbacik@xxxxxx>
Thanks,
Josef
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