Re: [PATCH 04/18] xfs: simplify xfs_aops_discard_page

Darrick J. Wong
2018-05-30T16:40:58Z

On Wed, May 30, 2018 at 11:59:59AM +0200, Christoph Hellwig wrote:
> Instead of looking at the buffer heads to see if a block is delalloc just
> call xfs_bmap_punch_delalloc_range on the whole page - this will leave
> any non-delalloc block intact and handle the iteration for us. As a side
> effect one more place stops caring about buffer heads and we can remove the
> xfs_check_page_type function entirely.
>
> 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 | 85 +++++------------------------------------------
> 1 file changed, 9 insertions(+), 76 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index c631c457b444..f2333e351e07 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -711,49 +711,6 @@ xfs_map_at_offset(
> clear_buffer_unwritten(bh);
> }
>
> -/*
> - * Test if a given page contains at least one buffer of a given @type.
> - * If @check_all_buffers is true, then we walk all the buffers in the page to
> - * try to find one of the type passed in. If it is not set, then the caller only
> - * needs to check the first buffer on the page for a match.
> - */
> -STATIC bool
> -xfs_check_page_type(
> - struct page *page,
> - unsigned int type,
> - bool check_all_buffers)
> -{
> - struct buffer_head *bh;
> - struct buffer_head *head;
> -
> - if (PageWriteback(page))
> - return false;
> - if (!page->mapping)
> - return false;
> - if (!page_has_buffers(page))
> - return false;
> -
> - bh = head = page_buffers(page);
> - do {
> - if (buffer_unwritten(bh)) {
> - if (type == XFS_IO_UNWRITTEN)
> - return true;
> - } else if (buffer_delay(bh)) {
> - if (type == XFS_IO_DELALLOC)
> - return true;
> - } else if (buffer_dirty(bh) && buffer_mapped(bh)) {
> - if (type == XFS_IO_OVERWRITE)
> - return true;
> - }
> -
> - /* If we are only checking the first buffer, we are done now. */
> - if (!check_all_buffers)
> - break;
> - } while ((bh = bh->b_this_page) != head);
> -
> - return false;
> -}
> -
> STATIC void
> xfs_vm_invalidatepage(
> struct page *page,
> @@ -785,9 +742,6 @@ xfs_vm_invalidatepage(
> * transaction. Indeed - if we get ENOSPC errors, we have to be able to do this
> * truncation without a transaction as there is no space left for block
> * reservation (typically why we see a ENOSPC in writeback).
> - *
> - * This is not a performance critical path, so for now just do the punching a
> - * buffer head at a time.
> */
> STATIC void
> xfs_aops_discard_page(
> @@ -795,47 +749,26 @@ xfs_aops_discard_page(
> {
> struct inode *inode = page->mapping->host;
> struct xfs_inode *ip = XFS_I(inode);
> - struct buffer_head *bh, *head;
> + struct xfs_mount *mp = ip->i_mount;
> loff_t offset = page_offset(page);
> + xfs_fileoff_t start_fsb = XFS_B_TO_FSBT(mp, offset);
> + int error;
>
> - if (!xfs_check_page_type(page, XFS_IO_DELALLOC, true))
> - goto out_invalidate;
> -
> - if (XFS_FORCED_SHUTDOWN(ip->i_mount))
> + if (XFS_FORCED_SHUTDOWN(mp))
> goto out_invalidate;
>
> - xfs_alert(ip->i_mount,
> + xfs_alert(mp,
> "page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
> page, ip->i_ino, offset);
>
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> - bh = head = page_buffers(page);
> - do {
> - int error;
> - xfs_fileoff_t start_fsb;
> -
> - if (!buffer_delay(bh))
> - goto next_buffer;
> -
> - start_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
> - error = xfs_bmap_punch_delalloc_range(ip, start_fsb, 1);
> - if (error) {
> - /* something screwed, just bail */
> - if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
> - xfs_alert(ip->i_mount,
> - "page discard unable to remove delalloc mapping.");
> - }
> - break;
> - }
> -next_buffer:
> - offset += i_blocksize(inode);
> -
> - } while ((bh = bh->b_this_page) != head);
> -
> + error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
> + PAGE_SIZE / i_blocksize(inode));
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + if (error && !XFS_FORCED_SHUTDOWN(mp))
> + xfs_alert(mp, "page discard unable to remove delalloc mapping.");
> out_invalidate:
> xfs_vm_invalidatepage(page, 0, PAGE_SIZE);
> - return;
> }
>
> static int