[PATCH v2] xfs: probe data buffer from page cache for unwritten extents

[Mark Tinguely]

On 06/25/12 07:41, Jeff Liu wrote:
> Hello,
>
> Using the start offset rather than map->br_startoff to calculate the starting page index could
> get more accurate data offset in page cache probe routine.
> With this refinement, the old max_t() could be able to remove too.
>
> Thanks Mark for pointing this out!
>
> -Jeff
>
>
> Cc: Mark Tinguely<tinguely at sgi.com>
> Signed-off-by: Jie Liu<jeff.liu at oracle.com>
>
> ---

> +			/*
> +			 * xfs_bmapi_read() can handle repeated hole regions,
> +			 * hence it should not return two extents both are
> +			 * holes.  If the 2nd extent is unwritten, there must
> +			 * have data buffer resides in page cache.
> +			 */
> +			BUG();


Looks great.

I hit the BUG() using a test with the following test:

  hole
  unwritten (treated as a hole)
  unwritten (treated as a hole)
  page of data.

I will send the current version of the test program.

--Mark.