[PATCH 04/18] xfs: simplify xfs_aops_discard_page

Christoph Hellwig
2018-05-30T10:00:38Z

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>
---
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
--
2.17.0