xfs: make attr removal an explicit operation

Parent pointers match attrs on name+value, unlike everything else which
matches on only the name.  Therefore, we cannot keep using the heuristic
that !value means remove.  Make this an explicit operation code.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_attr.c

@@ -916,10 +916,6 @@ xfs_attr_defer_add(
 	trace_xfs_attr_defer_add(new->xattri_dela_state, args->dp);
 }
 
-/*
- * Note: If args->value is NULL the attribute will be removed, just like the
- * Linux ->setattr API.
- */
 int
 xfs_attr_set(
 	struct xfs_da_args	*args,
@@ -955,7 +951,10 @@ xfs_attr_set(
 	args->op_flags = XFS_DA_OP_OKNOENT |
 					(args->op_flags & XFS_DA_OP_LOGGED);
 
-	if (args->value) {
+	switch (op) {
+	case XFS_ATTRUPDATE_UPSERT:
+	case XFS_ATTRUPDATE_CREATE:
+	case XFS_ATTRUPDATE_REPLACE:
 		XFS_STATS_INC(mp, xs_attr_set);
 		args->total = xfs_attr_calc_size(args, &local);
 
@@ -975,9 +974,11 @@ xfs_attr_set(
 
 		if (!local)
 			rmt_blks = xfs_attr3_rmt_blocks(mp, args->valuelen);
-	} else {
+		break;
+	case XFS_ATTRUPDATE_REMOVE:
 		XFS_STATS_INC(mp, xs_attr_remove);
 		rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
+		break;
 	}
 
 	/*
@@ -989,7 +990,7 @@ xfs_attr_set(
 	if (error)
 		return error;
 
-	if (args->value || xfs_inode_hasattr(dp)) {
+	if (op != XFS_ATTRUPDATE_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)
@@ -1002,7 +1003,7 @@ xfs_attr_set(
 	error = xfs_attr_lookup(args);
 	switch (error) {
 	case -EEXIST:
-		if (!args->value) {
+		if (op == XFS_ATTRUPDATE_REMOVE) {
 			/* if no value, we are performing a remove operation */
 			xfs_attr_defer_add(args, XFS_ATTRI_OP_FLAGS_REMOVE);
 			break;
@@ -1015,7 +1016,7 @@ xfs_attr_set(
 		break;
 	case -ENOATTR:
 		/* Can't remove what isn't there. */
-		if (!args->value)
+		if (op == XFS_ATTRUPDATE_REMOVE)
 			goto out_trans_cancel;
 
 		/* Pure replace fails if no existing attr to replace. */

fs/xfs/libxfs/xfs_attr.h

@@ -546,7 +546,8 @@ int xfs_attr_get_ilocked(struct xfs_da_args *args);
 int xfs_attr_get(struct xfs_da_args *args);
 
 enum xfs_attr_update {
-	XFS_ATTRUPDATE_UPSERTR,	/* set/remove value, replace any existing attr */
+	XFS_ATTRUPDATE_REMOVE,	/* remove attr */
+	XFS_ATTRUPDATE_UPSERT,	/* set value, replace any existing attr */
 	XFS_ATTRUPDATE_CREATE,	/* set value, fail if attr already exists */
 	XFS_ATTRUPDATE_REPLACE,	/* set value, fail if attr does not exist */
 };

fs/xfs/xfs_acl.c

@@ -201,16 +201,17 @@ __xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 		if (!args.value)
 			return -ENOMEM;
 		xfs_acl_to_disk(args.value, acl);
-	}
-
-	error = xfs_attr_change(&args, XFS_ATTRUPDATE_UPSERTR);
+		error = xfs_attr_change(&args, XFS_ATTRUPDATE_UPSERT);
 		kvfree(args.value);
-
+	} else {
+		error = xfs_attr_change(&args, XFS_ATTRUPDATE_REMOVE);
 		/*
 		 * If the attribute didn't exist to start with that's fine.
 		 */
-	if (!acl && error == -ENOATTR)
+		if (error == -ENOATTR)
 			error = 0;
+	}
+
 	if (!error)
 		set_cached_acl(inode, type, acl);
 	return error;

fs/xfs/xfs_ioctl.c

@@ -363,13 +363,16 @@ xfs_attr_filter(
 
 static inline enum xfs_attr_update
 xfs_xattr_flags(
-	u32			ioc_flags)
+	u32			ioc_flags,
+	void			*value)
 {
+	if (!value)
+		return XFS_ATTRUPDATE_REMOVE;
 	if (ioc_flags & XFS_IOC_ATTR_CREATE)
 		return XFS_ATTRUPDATE_CREATE;
 	if (ioc_flags & XFS_IOC_ATTR_REPLACE)
 		return XFS_ATTRUPDATE_REPLACE;
-	return XFS_ATTRUPDATE_UPSERTR;
+	return XFS_ATTRUPDATE_UPSERT;
 }
 
 int
@@ -526,7 +529,7 @@ xfs_attrmulti_attr_set(
 		args.valuelen = len;
 	}
 
-	error = xfs_attr_change(&args, xfs_xattr_flags(flags));
+	error = xfs_attr_change(&args, xfs_xattr_flags(flags, args.value));
 	if (!error && (flags & XFS_IOC_ATTR_ROOT))
 		xfs_forget_acl(inode, name);
 	kfree(args.value);

fs/xfs/xfs_iops.c

@@ -63,7 +63,7 @@ xfs_initxattrs(
 			.value		= xattr->value,
 			.valuelen	= xattr->value_len,
 		};
-		error = xfs_attr_change(&args, XFS_ATTRUPDATE_UPSERTR);
+		error = xfs_attr_change(&args, XFS_ATTRUPDATE_UPSERT);
 		if (error < 0)
 			break;
 	}

fs/xfs/xfs_xattr.c

@@ -118,13 +118,16 @@ xfs_xattr_get(const struct xattr_handler *handler, struct dentry *unused,
 
 static inline enum xfs_attr_update
 xfs_xattr_flags_to_op(
-	int		flags)
+	int		flags,
+	const void	*value)
 {
+	if (!value)
+		return XFS_ATTRUPDATE_REMOVE;
 	if (flags & XATTR_CREATE)
 		return XFS_ATTRUPDATE_CREATE;
 	if (flags & XATTR_REPLACE)
 		return XFS_ATTRUPDATE_REPLACE;
-	return XFS_ATTRUPDATE_UPSERTR;
+	return XFS_ATTRUPDATE_UPSERT;
 }
 
 static int
@@ -143,7 +146,7 @@ xfs_xattr_set(const struct xattr_handler *handler,
 	};
 	int			error;
 
-	error = xfs_attr_change(&args, xfs_xattr_flags_to_op(flags));
+	error = xfs_attr_change(&args, xfs_xattr_flags_to_op(flags, value));
 	if (!error && (handler->flags & XFS_ATTR_ROOT))
 		xfs_forget_acl(inode, name);
 	return error;