[PATCH 4/4] xfs: apply rt extent alignment constraints to cow extsize hint

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Even though reflink and copy-on-write aren't supported on the realtime
volume, if we ever turn that on, we'd still be constrained to the same
rt extent alignment requirements because cow involves remapping, and
we can only allocate and free in rtextsize units on the realtime volume.

At the moment there aren't any filesystems with rt and reflink in the
wild, so this is should be a zero-risk change.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_inode_buf.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 25261dd73290..704faf806e46 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -628,14 +628,21 @@ xfs_inode_validate_cowextsize(
 	uint16_t			flags,
 	uint64_t			flags2)
 {
-	bool				rt_flag;
+	bool				rt_flag, rtinherit_flag;
 	bool				hint_flag;
 	uint32_t			cowextsize_bytes;
+	uint32_t			blocksize_bytes;
 
 	rt_flag = (flags & XFS_DIFLAG_REALTIME);
+	rtinherit_flag = (flags & XFS_DIFLAG_RTINHERIT);
 	hint_flag = (flags2 & XFS_DIFLAG2_COWEXTSIZE);
 	cowextsize_bytes = XFS_FSB_TO_B(mp, cowextsize);
 
+	if (rt_flag || (rtinherit_flag && hint_flag))
+		blocksize_bytes = XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize);
+	else
+		blocksize_bytes = mp->m_sb.sb_blocksize;
+
 	if (hint_flag && !xfs_sb_version_hasreflink(&mp->m_sb))
 		return __this_address;
 
@@ -652,13 +659,13 @@ xfs_inode_validate_cowextsize(
 	if (hint_flag && rt_flag)
 		return __this_address;
 
-	if (cowextsize_bytes % mp->m_sb.sb_blocksize)
+	if (cowextsize_bytes % blocksize_bytes)
 		return __this_address;
 
 	if (cowextsize > MAXEXTLEN)
 		return __this_address;
 
-	if (cowextsize > mp->m_sb.sb_agblocks / 2)
+	if (!rt_flag && cowextsize > mp->m_sb.sb_agblocks / 2)
 		return __this_address;
 
 	return NULL;