[PATCH 15/20] xfs: use a union for i_cowextsize and i_flushiter

[Christoph Hellwig <hch@lst.de>]

The i_cowextsize field is only used for v3 inodes, and the i_flushiter
field is only used for v1/v2 inodes.  Use a union to pack the inode a
littler better after adding a few missing guards around their usage.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_inode_buf.c |  3 ++-
 fs/xfs/xfs_inode.c            |  6 ++++--
 fs/xfs/xfs_inode.h            |  7 +++++--
 fs/xfs/xfs_ioctl.c            | 15 +++++++++------
 4 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 3c7eb01c66ace4..88ec7be551a89d 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -193,7 +193,8 @@ xfs_inode_from_disk(
 	 * inode. If the inode is unused, mode is zero and we shouldn't mess
 	 * with the uninitialized part of it.
 	 */
-	ip->i_flushiter = be16_to_cpu(from->di_flushiter);
+	if (!xfs_sb_version_has_v3inode(&ip->i_mount->m_sb))
+		ip->i_flushiter = be16_to_cpu(from->di_flushiter);
 	inode->i_generation = be32_to_cpu(from->di_gen);
 	inode->i_mode = be16_to_cpu(from->di_mode);
 	if (!inode->i_mode)
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 06d779c9334b80..e483c380afd1db 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3483,8 +3483,10 @@ xfs_iflush(
 	xfs_inode_to_disk(ip, dip, iip->ili_item.li_lsn);
 
 	/* Wrap, we never let the log put out DI_MAX_FLUSH */
-	if (ip->i_flushiter == DI_MAX_FLUSH)
-		ip->i_flushiter = 0;
+	if (!xfs_sb_version_has_v3inode(&mp->m_sb)) {
+		if (ip->i_flushiter == DI_MAX_FLUSH)
+			ip->i_flushiter = 0;
+	}
 
 	xfs_iflush_fork(ip, dip, iip, XFS_DATA_FORK);
 	if (XFS_IFORK_Q(ip))
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index abe5b44b46220a..abb8672da0ceb4 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -58,8 +58,11 @@ typedef struct xfs_inode {
 	xfs_rfsblock_t		i_nblocks;	/* # of direct & btree blocks */
 	prid_t			i_projid;	/* owner's project id */
 	xfs_extlen_t		i_extsize;	/* basic/minimum extent size */
-	xfs_extlen_t		i_cowextsize;	/* basic cow extent size */
-	uint16_t		i_flushiter;	/* incremented on flush */
+	/* cowextsize is only used for v3 inodes, flushiter for v1/2 */
+	union {
+		xfs_extlen_t	i_cowextsize;	/* basic cow extent size */
+		uint16_t	i_flushiter;	/* incremented on flush */
+	};
 
 	struct xfs_icdinode	i_d;		/* most of ondisk inode */
 
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 7909e46b5c5a18..2028a4aa2bb20a 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1123,7 +1123,8 @@ xfs_fill_fsxattr(
 	simple_fill_fsxattr(fa, xfs_ip2xflags(ip));
 
 	fa->fsx_extsize = XFS_FSB_TO_B(mp, ip->i_extsize);
-	fa->fsx_cowextsize = XFS_FSB_TO_B(mp, ip->i_cowextsize);
+	if (ip->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE)
+		fa->fsx_cowextsize = XFS_FSB_TO_B(mp, ip->i_cowextsize);
 	fa->fsx_projid = ip->i_projid;
 	if (ifp && (ifp->if_flags & XFS_IFEXTENTS))
 		fa->fsx_nextents = xfs_iext_count(ifp);
@@ -1523,11 +1524,13 @@ xfs_ioctl_setattr(
 		ip->i_extsize = XFS_B_TO_FSB(mp, fa->fsx_extsize);
 	else
 		ip->i_extsize = 0;
-	if (xfs_sb_version_has_v3inode(&mp->m_sb) &&
-	    (ip->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE))
-		ip->i_cowextsize = XFS_B_TO_FSB(mp, fa->fsx_cowextsize);
-	else
-		ip->i_cowextsize = 0;
+
+	if (xfs_sb_version_has_v3inode(&mp->m_sb)) {
+		if (ip->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE)
+			ip->i_cowextsize = XFS_B_TO_FSB(mp, fa->fsx_cowextsize);
+		else
+			ip->i_cowextsize = 0;
+	}
 
 	error = xfs_trans_commit(tp);
 
-- 
2.30.1