[PATCH] Introduce SEEK_DATA/SEEK_HOLE support to XFS V6

[Mark Tinguely]

On 01/29/12 02:35, Jeff Liu wrote:
> Hello,
>
> Sorry for the delay!! I just got back from vacation.
>
> This is the V6 to introduce SEEK_DATA/SEEK_HOLE support to XFS.
> As we have discussed previously, I have removed the dirty data probing stuff and just treating unwritten extents as data in this post.
>
> Changes to V6:
> --------------
> * remove xfs_has_unwritten_buffer() for now.
> * xfs_bmapi_read() returns the br_state == XFS_EXT_NORM for a hole, so we need to check its startblock is not a "nullstartblock" in this case.
> * call i_size_read() after taking the ilock shared, otherwise, isize could be stale.
> * remove "ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK)" from xfs_seek_data() since it will not used.
> * in xfs_file_llseek(), return -EINVAL rather than -EOPNOTSUPP if whence is not valid according to http://linux.die.net/man/2/lseek.
> * s/int lock/uint lock/ in both xfs_seek_data() and xfs_seek_hole().
> * s/out_lock/out_unlock/ in both functions too.
>
> Tests:
> ------
> * seek_sanity_tester:
> http://permalink.gmane.org/gmane.comp.file-systems.xfs.general/42514
>
> *seek_copy_tester:
> http://permalink.gmane.org/gmane.comp.file-systems.xfs.general/42522
>
>
> Thank you!
> -Jeff
>
>
> Signed-off-by: Jie Liu<jeff.liu at oracle.com>
>
> ---
>   fs/xfs/xfs_file.c |  168 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>   1 files changed, 167 insertions(+), 1 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 753ed9b..41a045f 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> +STATIC loff_t
> +xfs_seek_data(
<deleted>
> +		error = xfs_bmapi_read(ip, fsbno, len - fsbno, map,&nmap,
> +				       XFS_BMAPI_ENTIRE);
> +		if (error)
> +			goto out_unlock;


> +STATIC loff_t
> +xfs_seek_hole(
<deleted>
> +	error = xfs_bmap_first_unused(NULL, ip, 1,&fsbno, XFS_DATA_FORK);
> +	if (error)
> +		goto out_unlock;

The code looks good for the reduced problem. It test correctly. I am 
still finding holes only if they start on a 16KB boundary which we 
discussed before. I mention it in case more advanced test cases are 
generated.

Question:
If the routines that are looking for extents/hole return an error (I see 
EFSCORRUPTED, EAGAIN, ENOMEM, EIO as possible errors in these routines), 
should you convert them to an error such as EIO? There is no specific 
error mention in the lseek manual page.

--Mark Tinguely.