tmpfs: Use xattr handler infrastructure

Use the VFS xattr handler infrastructure and get rid of similar code in
the filesystem.  For implementing shmem_xattr_handler_set, we need a
version of simple_xattr_set which removes the attribute when value is
NULL.  Use this to implement kernfs_iop_removexattr as well.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/kernfs/inode.c

@@ -205,7 +205,7 @@ int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
 	if (!attrs)
 		return -ENOMEM;
 
-	return simple_xattr_remove(&attrs->xattrs, name);
+	return simple_xattr_set(&attrs->xattrs, name, NULL, 0, XATTR_REPLACE);
 }
 
 ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,

fs/xattr.c

@@ -851,8 +851,22 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 	return ret;
 }
 
-static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
-			      const void *value, size_t size, int flags)
+/**
+ * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
+ * @xattrs: target simple_xattr list
+ * @name: name of the extended attribute
+ * @value: value of the xattr. If %NULL, will remove the attribute.
+ * @size: size of the new xattr
+ * @flags: %XATTR_{CREATE|REPLACE}
+ *
+ * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
+ * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
+ * otherwise, fails with -ENODATA.
+ *
+ * Returns 0 on success, -errno on failure.
+ */
+int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
+		     const void *value, size_t size, int flags)
 {
 	struct simple_xattr *xattr;
 	struct simple_xattr *new_xattr = NULL;
@@ -902,36 +916,6 @@ static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 
 }
 
-/**
- * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
- * @xattrs: target simple_xattr list
- * @name: name of the new extended attribute
- * @value: value of the new xattr. If %NULL, will remove the attribute
- * @size: size of the new xattr
- * @flags: %XATTR_{CREATE|REPLACE}
- *
- * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
- * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
- * otherwise, fails with -ENODATA.
- *
- * Returns 0 on success, -errno on failure.
- */
-int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
-		     const void *value, size_t size, int flags)
-{
-	if (size == 0)
-		value = ""; /* empty EA, do not remove */
-	return __simple_xattr_set(xattrs, name, value, size, flags);
-}
-
-/*
- * xattr REMOVE operation for in-memory/pseudo filesystems
- */
-int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
-{
-	return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
-}
-
 static bool xattr_is_trusted(const char *name)
 {
 	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);

include/linux/xattr.h

@@ -104,9 +104,7 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 		     void *buffer, size_t size);
 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 		     const void *value, size_t size, int flags);
-int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name);
-ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
-			  size_t size);
+ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer, size_t size);
 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 			   struct simple_xattr *new_xattr);
 

mm/shmem.c

@@ -2561,94 +2561,47 @@ static int shmem_initxattrs(struct inode *inode,
 	return 0;
 }
 
-static const struct xattr_handler *shmem_xattr_handlers[] = {
-#ifdef CONFIG_TMPFS_POSIX_ACL
-	&posix_acl_access_xattr_handler,
-	&posix_acl_default_xattr_handler,
-#endif
-	NULL
-};
-
-static int shmem_xattr_validate(const char *name)
-{
-	struct { const char *prefix; size_t len; } arr[] = {
-		{ XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
-		{ XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
-	};
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(arr); i++) {
-		size_t preflen = arr[i].len;
-		if (strncmp(name, arr[i].prefix, preflen) == 0) {
-			if (!name[preflen])
-				return -EINVAL;
-			return 0;
-		}
-	}
-	return -EOPNOTSUPP;
-}
-
-static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
-			      void *buffer, size_t size)
+static int shmem_xattr_handler_get(const struct xattr_handler *handler,
+				   struct dentry *dentry, const char *name,
+				   void *buffer, size_t size)
 {
 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
-	int err;
-
-	/*
-	 * If this is a request for a synthetic attribute in the system.*
-	 * namespace use the generic infrastructure to resolve a handler
-	 * for it via sb->s_xattr.
-	 */
-	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
-		return generic_getxattr(dentry, name, buffer, size);
-
-	err = shmem_xattr_validate(name);
-	if (err)
-		return err;
 
+	name = xattr_full_name(handler, name);
 	return simple_xattr_get(&info->xattrs, name, buffer, size);
 }
 
-static int shmem_setxattr(struct dentry *dentry, const char *name,
-			  const void *value, size_t size, int flags)
+static int shmem_xattr_handler_set(const struct xattr_handler *handler,
+				   struct dentry *dentry, const char *name,
+				   const void *value, size_t size, int flags)
 {
 	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
-	int err;
-
-	/*
-	 * If this is a request for a synthetic attribute in the system.*
-	 * namespace use the generic infrastructure to resolve a handler
-	 * for it via sb->s_xattr.
-	 */
-	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
-		return generic_setxattr(dentry, name, value, size, flags);
-
-	err = shmem_xattr_validate(name);
-	if (err)
-		return err;
 
+	name = xattr_full_name(handler, name);
 	return simple_xattr_set(&info->xattrs, name, value, size, flags);
 }
 
-static int shmem_removexattr(struct dentry *dentry, const char *name)
-{
-	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
-	int err;
-
-	/*
-	 * If this is a request for a synthetic attribute in the system.*
-	 * namespace use the generic infrastructure to resolve a handler
-	 * for it via sb->s_xattr.
-	 */
-	if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
-		return generic_removexattr(dentry, name);
+static const struct xattr_handler shmem_security_xattr_handler = {
+	.prefix = XATTR_SECURITY_PREFIX,
+	.get = shmem_xattr_handler_get,
+	.set = shmem_xattr_handler_set,
+};
 
-	err = shmem_xattr_validate(name);
-	if (err)
-		return err;
+static const struct xattr_handler shmem_trusted_xattr_handler = {
+	.prefix = XATTR_TRUSTED_PREFIX,
+	.get = shmem_xattr_handler_get,
+	.set = shmem_xattr_handler_set,
+};
 
-	return simple_xattr_remove(&info->xattrs, name);
-}
+static const struct xattr_handler *shmem_xattr_handlers[] = {
+#ifdef CONFIG_TMPFS_POSIX_ACL
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
+#endif
+	&shmem_security_xattr_handler,
+	&shmem_trusted_xattr_handler,
+	NULL
+};
 
 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
@@ -2661,10 +2614,10 @@ static const struct inode_operations shmem_short_symlink_operations = {
 	.readlink	= generic_readlink,
 	.follow_link	= simple_follow_link,
 #ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= shmem_setxattr,
-	.getxattr	= shmem_getxattr,
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
 	.listxattr	= shmem_listxattr,
-	.removexattr	= shmem_removexattr,
+	.removexattr	= generic_removexattr,
 #endif
 };
 
@@ -2673,10 +2626,10 @@ static const struct inode_operations shmem_symlink_inode_operations = {
 	.follow_link	= shmem_follow_link,
 	.put_link	= shmem_put_link,
 #ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= shmem_setxattr,
-	.getxattr	= shmem_getxattr,
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
 	.listxattr	= shmem_listxattr,
-	.removexattr	= shmem_removexattr,
+	.removexattr	= generic_removexattr,
 #endif
 };
 
@@ -3148,10 +3101,10 @@ static const struct inode_operations shmem_inode_operations = {
 	.getattr	= shmem_getattr,
 	.setattr	= shmem_setattr,
 #ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= shmem_setxattr,
-	.getxattr	= shmem_getxattr,
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
 	.listxattr	= shmem_listxattr,
-	.removexattr	= shmem_removexattr,
+	.removexattr	= generic_removexattr,
 	.set_acl	= simple_set_acl,
 #endif
 };
@@ -3170,10 +3123,10 @@ static const struct inode_operations shmem_dir_inode_operations = {
 	.tmpfile	= shmem_tmpfile,
 #endif
 #ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= shmem_setxattr,
-	.getxattr	= shmem_getxattr,
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
 	.listxattr	= shmem_listxattr,
-	.removexattr	= shmem_removexattr,
+	.removexattr	= generic_removexattr,
 #endif
 #ifdef CONFIG_TMPFS_POSIX_ACL
 	.setattr	= shmem_setattr,
@@ -3183,10 +3136,10 @@ static const struct inode_operations shmem_dir_inode_operations = {
 
 static const struct inode_operations shmem_special_inode_operations = {
 #ifdef CONFIG_TMPFS_XATTR
-	.setxattr	= shmem_setxattr,
-	.getxattr	= shmem_getxattr,
+	.setxattr	= generic_setxattr,
+	.getxattr	= generic_getxattr,
 	.listxattr	= shmem_listxattr,
-	.removexattr	= shmem_removexattr,
+	.removexattr	= generic_removexattr,
 #endif
 #ifdef CONFIG_TMPFS_POSIX_ACL
 	.setattr	= shmem_setattr,