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

[Mark Tinguely <tinguely@xxxxxxx>]

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@xxxxxxx>
> Signed-off-by: Jie Liu<jeff.liu@xxxxxxxxxx>
>
> ---
> +                       /*
> +                        * 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.