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>

1 files changed, 42 insertions, 89 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 9187eee4128b..fdfe6c8dddfc 100644
--- a/mm/shmem.c
+++ b/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,