[PATCH 13/18] 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            | 6 +++++-
 4 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index d090274fb8a152..96db2649f6b2fe 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 e951ea48b3a276..b4b6fddccd1ca0 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3459,8 +3459,10 @@ 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 6246ee8a4359ab..7ba0ffa50ede20 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 */
 	uint32_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 e45bce9b11082c..3405a5f5bacfda 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1121,7 +1121,11 @@ xfs_fill_fsxattr(
 
 	simple_fill_fsxattr(fa, xfs_ip2xflags(ip));
 	fa->fsx_extsize = ip->i_extsize << ip->i_mount->m_sb.sb_blocklog;
-	fa->fsx_cowextsize = ip->i_cowextsize << ip->i_mount->m_sb.sb_blocklog;
+	if (xfs_sb_version_has_v3inode(&ip->i_mount->m_sb) &&
+	    (ip->i_d.di_flags2 & XFS_DIFLAG2_COWEXTSIZE)) {
+		fa->fsx_cowextsize =
+			ip->i_cowextsize << ip->i_mount->m_sb.sb_blocklog;
+	}
 	fa->fsx_projid = ip->i_projid;
 	if (ifp && (ifp->if_flags & XFS_IFEXTENTS))
 		fa->fsx_nextents = xfs_iext_count(ifp);
-- 
2.30.1