On Wed, May 23, 2018 at 04:43:42PM +0200, Christoph Hellwig wrote:
> Instead of using xfs_bmapi_read to find delalloc extents and then punch
> them out using xfs_bunmapi, opencode the loop to iterate over the extents
> and call xfs_bmap_del_extent_delay directly. This both simplifies the
> code and reduces the number of extent tree lookups required.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_bmap_util.c | 78 ++++++++++++++----------------------------
> 1 file changed, 25 insertions(+), 53 deletions(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 06badcbadeb4..c009bdf9fdce 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
...
> @@ -708,63 +706,37 @@ xfs_bmap_punch_delalloc_range(
> xfs_fileoff_t start_fsb,
> xfs_fileoff_t length)
> {
> - xfs_fileoff_t remaining = length;
> + struct xfs_ifork *ifp = &ip->i_df;
> + struct xfs_bmbt_irec got, del;
> + struct xfs_iext_cursor icur;
> int error = 0;
>
> ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
>
> - do {
> - int done;
> - xfs_bmbt_irec_t imap;
> - int nimaps = 1;
> - xfs_fsblock_t firstblock;
> - struct xfs_defer_ops dfops;
> + if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> + error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
> + if (error)
> + return error;
> + }
>
> - /*
> - * Map the range first and check that it is a delalloc extent
> - * before trying to unmap the range. Otherwise we will be
> - * trying to remove a real extent (which requires a
> - * transaction) or a hole, which is probably a bad idea...
> - */
> - error = xfs_bmapi_read(ip, start_fsb, 1, &imap, &nimaps,
> - XFS_BMAPI_ENTIRE);
> + if (!xfs_iext_lookup_extent(ip, ifp, start_fsb, &icur, &got))
> + return 0;
>
> - if (error) {
> - /* something screwed, just bail */
> - if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
> - xfs_alert(ip->i_mount,
> - "Failed delalloc mapping lookup ino %lld fsb %lld.",
> - ip->i_ino, start_fsb);
> - }
> + do {
> + if (got.br_startoff >= start_fsb + length)
> break;
> - }
> - if (!nimaps) {
> - /* nothing there */
> - goto next_block;
> - }
> - if (imap.br_startblock != DELAYSTARTBLOCK) {
> - /* been converted, ignore */
> - goto next_block;
> - }
> - WARN_ON(imap.br_blockcount == 0);
> + if (!isnullstartblock(got.br_startblock))
> + continue;
>
> - /*
> - * Note: while we initialise the firstblock/dfops pair, they
> - * should never be used because blocks should never be
> - * allocated or freed for a delalloc extent and hence we need
> - * don't cancel or finish them after the xfs_bunmapi() call.
> - */
> - xfs_defer_init(&dfops, &firstblock);
> - error = xfs_bunmapi(NULL, ip, start_fsb, 1, 0, 1, &firstblock,
> - &dfops, &done);
> + del = got;
> + xfs_trim_extent(&del, start_fsb, length);
> + error = xfs_bmap_del_extent_delay(ip, XFS_DATA_FORK, &icur,
> + &got, &del);
> if (error)
> break;
> -
> - ASSERT(!xfs_defer_has_unfinished_work(&dfops));
> -next_block:
> - start_fsb++;
> - remaining--;
> - } while(remaining > 0);
> + if (!xfs_iext_get_extent(ifp, &icur, &got))
> + break;
Mostly looks Ok, but I'm not following what this get_extent() call is
for..? It also doesn't look like it would always do the right thing with
sub-page blocks. Consider a page with a couple discontig delalloc blocks
that happen to be the first extents in the file. The first
xfs_bmap_del_extent_delay() would do:
xfs_iext_remove(ip, icur, state);
xfs_iext_prev(ifp, icur);
... which I think sets cur->pos to -1, causes the get_extent() to fail
and thus fails to remove the subsequent delalloc blocks. Hm?
Brian
> + } while (xfs_iext_next_extent(ifp, &icur, &got));
>
> return error;
> }
> --
> 2.17.0
>
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