xfs: use XFS_IFORK_Q to determine the presence of an xattr fork

Modify xfs_ifork_ptr to return a NULL pointer if the caller asks for the
attribute fork but i_forkoff is zero.  This eliminates the ambiguity
between i_forkoff and i_af.if_present, which should make it easier to
understand the lifetime of attr forks.

While we're at it, remove the if_present checks around calls to
xfs_idestroy_fork and xfs_ifork_zap_attr since they can both handle attr
forks that have already been torn down.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

6 files changed, 2 insertions, 12 deletions

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index b661dc7600c8..8721d012e983 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -69,8 +69,6 @@ xfs_inode_hasattr(
 {
 	if (!XFS_IFORK_Q(ip))
 		return 0;
-	if (!ip->i_af.if_present)
-		return 0;
 	if (ip->i_af.if_format == XFS_DINODE_FMT_EXTENTS &&
 	    ip->i_af.if_nextents == 0)
 		return 0;
diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
index 0f100db504ee..36371c3b9069 100644
--- a/fs/xfs/libxfs/xfs_attr.h
+++ b/fs/xfs/libxfs/xfs_attr.h
@@ -576,7 +576,7 @@ xfs_attr_init_add_state(struct xfs_da_args *args)
 	 * context, i_af is guaranteed to exist. Hence if the attr fork is
 	 * null, we were called from a pure remove operation and so we are done.
 	 */
-	if (!args->dp->i_af.if_present)
+	if (!XFS_IFORK_Q(args->dp))
 		return XFS_DAS_DONE;
 
 	args->op_flags |= XFS_DA_OP_ADDNAME;
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 32dc74a04cc8..1ef72443025a 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1041,7 +1041,6 @@ xfs_bmap_add_attrfork(
 	error = xfs_bmap_set_attrforkoff(ip, size, &version);
 	if (error)
 		goto trans_cancel;
-	ASSERT(!ip->i_af.if_present);
 
 	xfs_ifork_init_attr(ip, XFS_DINODE_FMT_EXTENTS, 0);
 	logflags = 0;
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index dd11df5d3bf8..2f742a1b7c0a 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -177,7 +177,6 @@ xfs_inode_from_disk(
 	xfs_failaddr_t		fa;
 
 	ASSERT(ip->i_cowfp == NULL);
-	ASSERT(!ip->i_af.if_present);
 
 	fa = xfs_dinode_verify(ip->i_mount, ip->i_ino, from);
 	if (fa) {
diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 9d5141c21eee..b0370b837166 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -282,9 +282,6 @@ xfs_ifork_init_attr(
 	enum xfs_dinode_fmt	format,
 	xfs_extnum_t		nextents)
 {
-	ASSERT(!ip->i_af.if_present);
-
-	ip->i_af.if_present = 1;
 	ip->i_af.if_format = format;
 	ip->i_af.if_nextents = nextents;
 }
@@ -293,7 +290,6 @@ void
 xfs_ifork_zap_attr(
 	struct xfs_inode	*ip)
 {
-	ASSERT(ip->i_af.if_present);
 	ASSERT(ip->i_af.if_broot == NULL);
 	ASSERT(ip->i_af.if_u1.if_data == NULL);
 	ASSERT(ip->i_af.if_height == 0);
@@ -683,7 +679,6 @@ xfs_ifork_init_cow(
 
 	ip->i_cowfp = kmem_cache_zalloc(xfs_ifork_cache,
 				       GFP_NOFS | __GFP_NOFAIL);
-	ip->i_cowfp->if_present = 1;
 	ip->i_cowfp->if_format = XFS_DINODE_FMT_EXTENTS;
 }
 
@@ -722,7 +717,7 @@ xfs_ifork_verify_local_attr(
 	struct xfs_ifork	*ifp = &ip->i_af;
 	xfs_failaddr_t		fa;
 
-	if (!ifp->if_present)
+	if (!XFS_IFORK_Q(ip))
 		fa = __this_address;
 	else
 		fa = xfs_attr_shortform_verify(ip);
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 63015e9cee14..0b912bbe4f4b 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -24,7 +24,6 @@ struct xfs_ifork {
 	xfs_extnum_t		if_nextents;	/* # of extents in this fork */
 	short			if_broot_bytes;	/* bytes allocated for root */
 	int8_t			if_format;	/* format of this fork */
-	int8_t			if_present;	/* 1 if present */
 };
 
 /*