[PATCH v2 06/11] xfs: Reflink CoW-based atomic write support

[John Garry <john.g.garry@oracle.com>]

For CoW-based atomic write support, always allocate a cow hole in
xfs_reflink_allocate_cow() to write the new data.

The semantics is that if @atomic is set, we will be passed a CoW fork
extent mapping for no error returned.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/xfs_iomap.c   |  2 +-
 fs/xfs/xfs_reflink.c | 12 +++++++-----
 fs/xfs/xfs_reflink.h |  2 +-
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index d61460309a78..ab79f0080288 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -865,7 +865,7 @@ xfs_direct_write_iomap_begin(
 		/* may drop and re-acquire the ilock */
 		error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
 				&lockmode,
-				(flags & IOMAP_DIRECT) || IS_DAX(inode));
+				(flags & IOMAP_DIRECT) || IS_DAX(inode), false);
 		if (error)
 			goto out_unlock;
 		if (shared)
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 8428f7b26ee6..3dab3ba900a3 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -435,7 +435,8 @@ xfs_reflink_fill_cow_hole(
 	struct xfs_bmbt_irec	*cmap,
 	bool			*shared,
 	uint			*lockmode,
-	bool			convert_now)
+	bool			convert_now,
+	bool			atomic)
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_trans	*tp;
@@ -466,7 +467,7 @@ xfs_reflink_fill_cow_hole(
 	*lockmode = XFS_ILOCK_EXCL;
 
 	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
-	if (error || !*shared)
+	if (error || (!*shared && !atomic))
 		goto out_trans_cancel;
 
 	if (found) {
@@ -566,7 +567,8 @@ xfs_reflink_allocate_cow(
 	struct xfs_bmbt_irec	*cmap,
 	bool			*shared,
 	uint			*lockmode,
-	bool			convert_now)
+	bool			convert_now,
+	bool 			atomic)
 {
 	int			error;
 	bool			found;
@@ -578,7 +580,7 @@ xfs_reflink_allocate_cow(
 	}
 
 	error = xfs_find_trim_cow_extent(ip, imap, cmap, shared, &found);
-	if (error || !*shared)
+	if (error || (!*shared && !atomic))
 		return error;
 
 	/* CoW fork has a real extent */
@@ -592,7 +594,7 @@ xfs_reflink_allocate_cow(
 	 */
 	if (cmap->br_startoff > imap->br_startoff)
 		return xfs_reflink_fill_cow_hole(ip, imap, cmap, shared,
-				lockmode, convert_now);
+				lockmode, convert_now, atomic);
 
 	/*
 	 * CoW fork has a delalloc reservation. Replace it with a real extent.
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index cc4e92278279..754d2bb692d3 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -32,7 +32,7 @@ int xfs_bmap_trim_cow(struct xfs_inode *ip, struct xfs_bmbt_irec *imap,
 
 int xfs_reflink_allocate_cow(struct xfs_inode *ip, struct xfs_bmbt_irec *imap,
 		struct xfs_bmbt_irec *cmap, bool *shared, uint *lockmode,
-		bool convert_now);
+		bool convert_now, bool atomic);
 extern int xfs_reflink_convert_cow(struct xfs_inode *ip, xfs_off_t offset,
 		xfs_off_t count);
 
-- 
2.31.1