Re: [PATCH 18/18] xfs: allow writeback on pages without buffer heads

Darrick J. Wong
2018-05-30T18:08:55Z

On Wed, May 30, 2018 at 12:00:13PM +0200, Christoph Hellwig wrote:
> Disable the IOMAP_F_BUFFER_HEAD flag on file systems with a block size
> equal to the page size, and deal with pages without buffer heads in
> writeback. Thanks to the previous refactoring this is basically trivial
> now.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
> fs/xfs/xfs_aops.c | 47 +++++++++++++++++++++++++++++++++-------------
> fs/xfs/xfs_iomap.c | 3 ++-
> 2 files changed, 36 insertions(+), 14 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 84f88cecd2f1..6640377b6eae 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -91,6 +91,19 @@ xfs_find_daxdev_for_inode(
> return mp->m_ddev_targp->bt_daxdev;
> }
>
> +static void
> +xfs_finish_page_writeback(
> + struct inode *inode,
> + struct bio_vec *bvec,
> + int error)
> +{
> + if (error) {
> + SetPageError(bvec->bv_page);
> + mapping_set_error(inode->i_mapping, -EIO);
> + }
> + end_page_writeback(bvec->bv_page);
> +}
> +
> /*
> * We're now finished for good with this page. Update the page state via the
> * associated buffer_heads, paying attention to the start and end offsets that
> @@ -103,7 +116,7 @@ xfs_find_daxdev_for_inode(
> * and buffers potentially freed after every call to end_buffer_async_write.
> */
> static void
> -xfs_finish_page_writeback(
> +xfs_finish_buffer_writeback(
> struct inode *inode,
> struct bio_vec *bvec,
> int error)
> @@ -178,9 +191,12 @@ xfs_destroy_ioend(
> next = bio->bi_private;
>
> /* walk each page on bio, ending page IO on them */
> - bio_for_each_segment_all(bvec, bio, i)
> - xfs_finish_page_writeback(inode, bvec, error);
> -
> + bio_for_each_segment_all(bvec, bio, i) {
> + if (page_has_buffers(bvec->bv_page))
> + xfs_finish_buffer_writeback(inode, bvec, error);
> + else
> + xfs_finish_page_writeback(inode, bvec, error);
> + }
> bio_put(bio);
> }
>
> @@ -782,13 +798,16 @@ xfs_writepage_map(
> {
> LIST_HEAD(submit_list);
> struct xfs_ioend *ioend, *next;
> - struct buffer_head *bh;
> + struct buffer_head *bh = NULL;
> ssize_t len = i_blocksize(inode);
> int error = 0;
> int count = 0;
> loff_t file_offset; /* file offset of page */
> unsigned poffset; /* offset into page */
>
> + if (page_has_buffers(page))
> + bh = page_buffers(page);
> +
> /*
> * Walk the blocks on the page, and we we run off then end of the
> * current map or find the current map invalid, grab a new one.
> @@ -797,11 +816,9 @@ xfs_writepage_map(
> * replace the bufferhead with some other state tracking mechanism in
> * future.
> */
> - file_offset = page_offset(page);
> - bh = page_buffers(page);
> - for (poffset = 0;
> + for (poffset = 0, file_offset = page_offset(page);
> poffset < PAGE_SIZE;
> - poffset += len, file_offset += len, bh = bh->b_this_page) {
> + poffset += len, file_offset += len) {
> /* past the range we are writing, so nothing more to write. */
> if (file_offset >= end_offset)
> break;
> @@ -809,9 +826,10 @@ xfs_writepage_map(
> /*
> * Block does not contain valid data, skip it.
> */
> - if (!buffer_uptodate(bh)) {
> + if (bh && !buffer_uptodate(bh)) {
> if (PageUptodate(page))
> ASSERT(buffer_mapped(bh));
> + bh = bh->b_this_page;
> continue;
> }
>
> @@ -836,10 +854,15 @@ xfs_writepage_map(
> * meaningless for holes (!mapped && uptodate), so check we did
> * have a buffer covering a hole here and continue.
> */
> + if (bh)
> + bh = bh->b_this_page;
> continue;
> }
>
> - xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
> + if (bh) {
> + xfs_map_at_offset(inode, bh, &wpc->imap, file_offset);
> + bh = bh->b_this_page;
> + }
> xfs_add_to_ioend(inode, file_offset, page, wpc, wbc,
> &submit_list);
> count++;
> @@ -939,8 +962,6 @@ xfs_do_writepage(
>
> trace_xfs_writepage(inode, page, 0, 0);
>
> - ASSERT(page_has_buffers(page));
> -
> /*
> * Refuse to write the page out if we are called from reclaim context.
> *
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index f949f0dd7382..93c40da3378a 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -1031,7 +1031,8 @@ xfs_file_iomap_begin(
> if (XFS_FORCED_SHUTDOWN(mp))
> return -EIO;
>
> - iomap->flags |= IOMAP_F_BUFFER_HEAD;
> + if (i_blocksize(inode) < PAGE_SIZE)
> + iomap->flags |= IOMAP_F_BUFFER_HEAD;
>
> if (((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == IOMAP_WRITE) &&
> !IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {