[PATCH 101/119] xfs: promote buffered writes to CoW when cowextsz is set

Darrick J. Wong
2016-06-17T01:28:50Z

When we're doing non-cow writes to a part of a file that already has a
CoW reservation by virtue of cowextsz being set, promote the write to
copy-on-write so that the entire extent can get written out as a single
block, thereby reducing post-CoW fragmentation.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_aops.c | 39 ++++++++++++++++++---------------------
1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 812bae5..31205fa 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -668,10 +668,12 @@ xfs_check_page_type(
bh = head = page_buffers(page);
do {
if (buffer_unwritten(bh)) {
- if (type == XFS_IO_UNWRITTEN)
+ if (type == XFS_IO_UNWRITTEN ||
+ type == XFS_IO_COW)
return true;
} else if (buffer_delay(bh)) {
- if (type == XFS_IO_DELALLOC)
+ if (type == XFS_IO_DELALLOC ||
+ type == XFS_IO_COW)
return true;
} else if (buffer_dirty(bh) && buffer_mapped(bh)) {
if (type == XFS_IO_OVERWRITE ||
@@ -836,25 +838,13 @@ xfs_writepage_map(
continue;
}

- if (buffer_unwritten(bh)) {
- if (wpc->io_type != XFS_IO_UNWRITTEN) {
- wpc->io_type = XFS_IO_UNWRITTEN;
- wpc->imap_valid = false;
- }
- } else if (buffer_delay(bh)) {
- if (wpc->io_type != XFS_IO_DELALLOC) {
- wpc->io_type = XFS_IO_DELALLOC;
- wpc->imap_valid = false;
- }
- } else if (buffer_uptodate(bh)) {
- new_type = xfs_is_cow_io(XFS_I(inode), offset) ?
- XFS_IO_COW : XFS_IO_OVERWRITE;
-
- if (wpc->io_type != new_type) {
- wpc->io_type = new_type;
- wpc->imap_valid = false;
- }
- } else {
+ if (buffer_unwritten(bh))
+ new_type = XFS_IO_UNWRITTEN;
+ else if (buffer_delay(bh))
+ new_type = XFS_IO_DELALLOC;
+ else if (buffer_uptodate(bh))
+ new_type = XFS_IO_OVERWRITE;
+ else {
if (PageUptodate(page))
ASSERT(buffer_mapped(bh));
/*
@@ -867,6 +857,13 @@ xfs_writepage_map(
continue;
}

+ if (xfs_is_cow_io(XFS_I(inode), offset))
+ new_type = XFS_IO_COW;
+ if (wpc->io_type != new_type) {
+ wpc->io_type = new_type;
+ wpc->imap_valid = false;
+ }
+
if (wpc->imap_valid)
wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap,
offset);