On Thu, Jun 05, 2025 at 01:33:55PM -0400, Brian Foster wrote:
> Use the iomap folio batch mechanism to select folios to zero on zero
> range of unwritten mappings. Trim the resulting mapping if the batch
> is filled (unlikely for current use cases) to distinguish between a
> range to skip and one that requires another iteration due to a full
> batch.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/xfs_iomap.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index b5cf5bc6308d..63054f7ead0e 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -1691,6 +1691,8 @@ xfs_buffered_write_iomap_begin(
> struct iomap *iomap,
> struct iomap *srcmap)
> {
> + struct iomap_iter *iter = container_of(iomap, struct iomap_iter,
> + iomap);
/me has been wondering more and more if we should just pass the iter
directly to iomap_begin rather than make them play these container_of
tricks... OTOH I think the whole point of this:
ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags,
&iter->iomap, &iter->srcmap);
is to "avoid" allowing the iomap users to mess with the internals of the
iomap iter...
> struct xfs_inode *ip = XFS_I(inode);
> struct xfs_mount *mp = ip->i_mount;
> xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
> @@ -1762,6 +1764,7 @@ xfs_buffered_write_iomap_begin(
> */
> if (flags & IOMAP_ZERO) {
> xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
> + u64 end;
>
> if (isnullstartblock(imap.br_startblock) &&
> offset_fsb >= eof_fsb)
> @@ -1769,6 +1772,26 @@ xfs_buffered_write_iomap_begin(
> if (offset_fsb < eof_fsb && end_fsb > eof_fsb)
> end_fsb = eof_fsb;
>
> + /*
> + * Look up dirty folios for unwritten mappings within EOF.
> + * Providing this bypasses the flush iomap uses to trigger
> + * extent conversion when unwritten mappings have dirty
> + * pagecache in need of zeroing.
> + *
> + * Trim the mapping to the end pos of the lookup, which in turn
> + * was trimmed to the end of the batch if it became full before
> + * the end of the mapping.
> + */
> + if (imap.br_state == XFS_EXT_UNWRITTEN &&
> + offset_fsb < eof_fsb) {
> + loff_t len = min(count,
> + XFS_FSB_TO_B(mp, imap.br_blockcount));
> +
> + end = iomap_fill_dirty_folios(iter, offset, len);
...though I wonder, does this need to happen in
xfs_buffered_write_iomap_begin? Is it required to hold the ILOCK while
we go look for folios in the mapping? Or could this become a part of
iomap_write_begin?
--D
> + end_fsb = min_t(xfs_fileoff_t, end_fsb,
> + XFS_B_TO_FSB(mp, end));
> + }
> +
> xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
> }
>
> --
> 2.49.0
>
>
