xattr handlers: Simplify list operation

Change the list operation to only return whether or not an attribute
should be listed.  Copying the attribute names into the buffer is moved
to the callers.

Since the result only depends on the dentry and not on the attribute
name, we do not pass the attribute name to list operations.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 17 insertions, 56 deletions

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 6b6b3e751f8c..e9b9afdd1d96 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -404,19 +404,24 @@ ext4_xattr_list_entries(struct dentry *dentry, struct ext4_xattr_entry *entry,
 		const struct xattr_handler *handler =
 			ext4_xattr_handler(entry->e_name_index);
 
-		if (handler) {
-			size_t size = handler->list(handler, dentry, buffer,
-						    rest, entry->e_name,
-						    entry->e_name_len);
+		if (handler && (!handler->list || handler->list(dentry))) {
+			const char *prefix = handler->prefix ?: handler->name;
+			size_t prefix_len = strlen(prefix);
+			size_t size = prefix_len + entry->e_name_len + 1;
+
 			if (buffer) {
 				if (size > rest)
 					return -ERANGE;
-				buffer += size;
+				memcpy(buffer, prefix, prefix_len);
+				buffer += prefix_len;
+				memcpy(buffer, entry->e_name, entry->e_name_len);
+				buffer += entry->e_name_len;
+				*buffer++ = 0;
 			}
 			rest -= size;
 		}
 	}
-	return buffer_size - rest;
+	return buffer_size - rest;  /* total size */
 }
 
 static int
diff --git a/fs/ext4/xattr_security.c b/fs/ext4/xattr_security.c
index 195abc4a88bb..3e81bdca071a 100644
--- a/fs/ext4/xattr_security.c
+++ b/fs/ext4/xattr_security.c
@@ -11,23 +11,6 @@
 #include "ext4.h"
 #include "xattr.h"
 
-static size_t
-ext4_xattr_security_list(const struct xattr_handler *handler,
-			 struct dentry *dentry, char *list, size_t list_size,
-			 const char *name, size_t name_len)
-{
-	const size_t prefix_len = sizeof(XATTR_SECURITY_PREFIX)-1;
-	const size_t total_len = prefix_len + name_len + 1;
-
-
-	if (list && total_len <= list_size) {
-		memcpy(list, XATTR_SECURITY_PREFIX, prefix_len);
-		memcpy(list+prefix_len, name, name_len);
-		list[prefix_len + name_len] = '\0';
-	}
-	return total_len;
-}
-
 static int
 ext4_xattr_security_get(const struct xattr_handler *handler,
 			struct dentry *dentry, const char *name,
@@ -75,7 +58,6 @@ ext4_init_security(handle_t *handle, struct inode *inode, struct inode *dir,
 
 const struct xattr_handler ext4_xattr_security_handler = {
 	.prefix	= XATTR_SECURITY_PREFIX,
-	.list	= ext4_xattr_security_list,
 	.get	= ext4_xattr_security_get,
 	.set	= ext4_xattr_security_set,
 };
diff --git a/fs/ext4/xattr_trusted.c b/fs/ext4/xattr_trusted.c
index 121fdf9fdc02..2a3c6f9b8cb8 100644
--- a/fs/ext4/xattr_trusted.c
+++ b/fs/ext4/xattr_trusted.c
@@ -12,23 +12,10 @@
 #include "ext4.h"
 #include "xattr.h"
 
-static size_t
-ext4_xattr_trusted_list(const struct xattr_handler *handler,
-			struct dentry *dentry, char *list, size_t list_size,
-			const char *name, size_t name_len)
+static bool
+ext4_xattr_trusted_list(struct dentry *dentry)
 {
-	const size_t prefix_len = XATTR_TRUSTED_PREFIX_LEN;
-	const size_t total_len = prefix_len + name_len + 1;
-
-	if (!capable(CAP_SYS_ADMIN))
-		return 0;
-
-	if (list && total_len <= list_size) {
-		memcpy(list, XATTR_TRUSTED_PREFIX, prefix_len);
-		memcpy(list+prefix_len, name, name_len);
-		list[prefix_len + name_len] = '\0';
-	}
-	return total_len;
+	return capable(CAP_SYS_ADMIN);
 }
 
 static int
diff --git a/fs/ext4/xattr_user.c b/fs/ext4/xattr_user.c
index 577fc122d884..d152f431e432 100644
--- a/fs/ext4/xattr_user.c
+++ b/fs/ext4/xattr_user.c
@@ -11,23 +11,10 @@
 #include "ext4.h"
 #include "xattr.h"
 
-static size_t
-ext4_xattr_user_list(const struct xattr_handler *handler,
-		     struct dentry *dentry, char *list, size_t list_size,
-		     const char *name, size_t name_len)
+static bool
+ext4_xattr_user_list(struct dentry *dentry)
 {
-	const size_t prefix_len = XATTR_USER_PREFIX_LEN;
-	const size_t total_len = prefix_len + name_len + 1;
-
-	if (!test_opt(dentry->d_sb, XATTR_USER))
-		return 0;
-
-	if (list && total_len <= list_size) {
-		memcpy(list, XATTR_USER_PREFIX, prefix_len);
-		memcpy(list+prefix_len, name, name_len);
-		list[prefix_len + name_len] = '\0';
-	}
-	return total_len;
+	return test_opt(dentry->d_sb, XATTR_USER);
 }
 
 static int