[PATCH 02/17] xfs: make xfs_attr_set require XFS_DA_OP_REMOVE

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Quite a few patches from now, we're going to change the parent pointer
xattr format to encode as much of the dirent name in the xattr name as
fits, and spill the rest of it to the xattr value.  To make this work
correctly, we'll be adding the ability to look up xattrs based on name
/and/ value.

Internally, the xattr data structure supports attributes with a zero
length value, which is how we're going to store parent pointers for
short dirent names.  The parent pointer repair code uses xfs_attr_set to
add missing and remove dangling parent pointers, so that interface must
be capable of setting an xattr with args->value == NULL.

The userspace API doesn't support this, so xfs_attr_set currently treats
a NULL args->value as a request to remove an attr.  However, that's a
quirk of the existing callers and the interface.  Make the callers of
xfs_attr_set to declare explicitly that they want to remove an xattr.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_attr.c   |    9 +++++----
 fs/xfs/libxfs/xfs_parent.c |    1 +
 fs/xfs/xfs_xattr.c         |    5 +++++
 3 files changed, 11 insertions(+), 4 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 3065dd622102..756d93526075 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -977,6 +977,7 @@ xfs_attr_set(
 	struct xfs_inode	*dp = args->dp;
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_trans_res	tres;
+	bool			is_remove = args->op_flags & XFS_DA_OP_REMOVE;
 	bool			rsvd;
 	int			error, local;
 	int			rmt_blks = 0;
@@ -1004,7 +1005,7 @@ xfs_attr_set(
 	args->op_flags = XFS_DA_OP_OKNOENT |
 					(args->op_flags & XFS_DA_OP_LOGGED);
 
-	if (args->value) {
+	if (!is_remove) {
 		XFS_STATS_INC(mp, xs_attr_set);
 		args->total = xfs_attr_calc_size(args, &local);
 
@@ -1038,7 +1039,7 @@ xfs_attr_set(
 	if (error)
 		return error;
 
-	if (args->value || xfs_inode_hasattr(dp)) {
+	if (!is_remove || xfs_inode_hasattr(dp)) {
 		error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
 				XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
 		if (error == -EFBIG)
@@ -1052,7 +1053,7 @@ xfs_attr_set(
 	switch (error) {
 	case -EEXIST:
 		/* if no value, we are performing a remove operation */
-		if (!args->value) {
+		if (is_remove) {
 			error = xfs_attr_defer_remove(args);
 			break;
 		}
@@ -1064,7 +1065,7 @@ xfs_attr_set(
 		break;
 	case -ENOATTR:
 		/* Can't remove what isn't there. */
-		if (!args->value)
+		if (is_remove)
 			goto out_trans_cancel;
 
 		/* Pure replace fails if no existing attr to replace. */
diff --git a/fs/xfs/libxfs/xfs_parent.c b/fs/xfs/libxfs/xfs_parent.c
index a2575bf44c89..96ce5de8508a 100644
--- a/fs/xfs/libxfs/xfs_parent.c
+++ b/fs/xfs/libxfs/xfs_parent.c
@@ -384,6 +384,7 @@ xfs_parent_unset(
 	scr->args.geo		= ip->i_mount->m_attr_geo;
 	scr->args.name		= (const unsigned char *)&scr->rec;
 	scr->args.namelen	= sizeof(struct xfs_parent_name_rec);
+	scr->args.op_flags	= XFS_DA_OP_REMOVE;
 	scr->args.whichfork	= XFS_ATTR_FORK;
 
 	return xfs_attr_set(&scr->args);
diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
index b92fc38bd550..46de0e2bfc46 100644
--- a/fs/xfs/xfs_xattr.c
+++ b/fs/xfs/xfs_xattr.c
@@ -103,6 +103,11 @@ xfs_attr_change(
 		use_logging = true;
 	}
 
+	if (args->value)
+		args->op_flags &= ~XFS_DA_OP_REMOVE;
+	else
+		args->op_flags |= XFS_DA_OP_REMOVE;
+
 	error = xfs_attr_set(args);
 
 	if (use_logging)