On Thu, Jul 26, 2012 at 04:56:22PM +0800, Jeff Liu wrote:
> Search possbile hole offset for given range from page cache for unwritten and delayed-allocation extents.
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
>
> ---
> fs/xfs/xfs_file.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 80 insertions(+), 10 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 15acd4d..1b83549 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1296,9 +1296,9 @@ xfs_seek_hole(
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> loff_t uninitialized_var(offset);
> - loff_t holeoff;
> xfs_fsize_t isize;
> xfs_fileoff_t fsbno;
> + xfs_filblks_t end;
> uint lock;
> int error;
>
> @@ -1314,20 +1314,90 @@ xfs_seek_hole(
> }
>
> fsbno = XFS_B_TO_FSBT(mp, start);
> - error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);
> - if (error)
> - goto out_unlock;
> + end = XFS_B_TO_FSB(mp, isize);
> +
> + for (;;) {
> + struct xfs_bmbt_irec map[2];
> + int nmap = 2;
> +
> + error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
> + XFS_BMAPI_ENTIRE);
> + if (error)
> + goto out_unlock;
> +
> + /* No extents at given offset, must be beyond EOF */
> + if (nmap == 0) {
> + error = ENXIO;
> + goto out_unlock;
> + }
>
> - holeoff = XFS_FSB_TO_B(mp, fsbno);
> - if (holeoff <= start)
> offset = start;
> - else {
> + /* Landed in a hole, return */
> + if (map[0].br_startblock == HOLESTARTBLOCK)
> + break;
> + else {
> + /*
> + * Landed in an unwritten extent, try to lookup page
> + * cache to find holes.
> + */
Laned in a data extent is more correct here.
> + if (map[0].br_state == XFS_EXT_UNWRITTEN ||
> + isnullstartblock(map[0].br_startblock)) {
> + /* Probing page cache start from offset */
> + if (xfs_find_get_desired_pgoff(inode, &map[0],
> + HOLE_OFF, &offset))
> + break;
> + }
Same logic changes as previous patch:
if (map[0].br_startblock == HOLESTARTBLOCK)
break;
else if (map[0].br_state == XFS_EXT_UNWRITTEN) {
ASSERT(!isnullstartblock(map[0].br_startblock));
/* Probing page cache start from offset */
if (xfs_find_get_desired_pgoff(inode, &map[0],
HOLE_OFF, &offset))
break;
} else {
.....
> /*
> - * xfs_bmap_first_unused() could return a value bigger than
> - * isize if there are no more holes past the supplied offset.
> + * Both mappings contains data, proceed to the next round of
> + * search if the current reading offset not beyond or hit EOF.
> */
> - offset = min_t(loff_t, holeoff, isize);
> + fsbno = map[1].br_startoff + map[1].br_blockcount;
> + start = XFS_FSB_TO_B(mp, fsbno);
> + if (start >= isize) {
> + offset = isize;
> + break;
> + }
And that check can move to the start of the loop, too.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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