On Mon, Dec 03, 2018 at 05:24:59PM -0500, Christoph Hellwig wrote:
> This only matters if we want to write data through the COW fork that is
> not actually an overwrite of existing data. Reasons for that are
> speculative COW fork allocations using the cowextsize, or a mode where
> we always write through the COW fork. Currently both can't actually
> happen, but I plan to enable them.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_aops.c | 31 ++++++++++++++++---------------
> 1 file changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 124b8de37115..7d95a84064e7 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -403,28 +403,29 @@ xfs_map_blocks(
>
> wpc->fork = XFS_DATA_FORK;
>
> + /* landed in a hole or beyond EOF? */
> if (imap.br_startoff > offset_fsb) {
> - /* landed in a hole or beyond EOF */
> imap.br_blockcount = imap.br_startoff - offset_fsb;
> imap.br_startoff = offset_fsb;
> imap.br_startblock = HOLESTARTBLOCK;
> imap.br_state = XFS_EXT_NORM;
> - } else {
> - /*
> - * Truncate to the next COW extent if there is one. This is the
> - * only opportunity to do this because we can skip COW fork
> - * lookups for the subsequent blocks in the mapping; however,
> - * the requirement to treat the COW range separately remains.
> - */
> - if (cow_fsb != NULLFILEOFF &&
> - cow_fsb < imap.br_startoff + imap.br_blockcount)
> - imap.br_blockcount = cow_fsb - imap.br_startoff;
> -
> - /* got a delalloc extent? */
> - if (isnullstartblock(imap.br_startblock))
> - goto allocate_blocks;
> }
>
> + /*
> + * Truncate to the next COW extent if there is one. This is the only
> + * opportunity to do this because we can skip COW fork lookups for the
> + * subsequent blocks in the mapping; however, the requirement to treat
> + * the COW range separately remains.
> + */
> + if (cow_fsb != NULLFILEOFF &&
> + cow_fsb < imap.br_startoff + imap.br_blockcount)
> + imap.br_blockcount = cow_fsb - imap.br_startoff;
> +
> + /* got a delalloc extent? */
> + if (imap.br_startblock != HOLESTARTBLOCK &&
> + isnullstartblock(imap.br_startblock))
> + goto allocate_blocks;
> +
> wpc->imap = imap;
> trace_xfs_map_blocks_found(ip, offset, count, wpc->fork, &imap);
> return 0;
> --
> 2.19.1
>
