2 files changed, 15 insertions, 7 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0c0edacbc14c..245952cf7650 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -451,9 +451,9 @@ struct btrfs_root {
 /*
  * Inode flags
  */
-#define BTRFS_INODE_NODATASUM           0x1
-#define BTRFS_INODE_NODATACOW           0x2
-
+#define BTRFS_INODE_NODATASUM           (1 << 0)
+#define BTRFS_INODE_NODATACOW           (1 << 1)
+#define BTRFS_INODE_READONLY            (1 << 2)
 #define btrfs_clear_flag(inode, flag)   (BTRFS_I(inode)->flags &= \
                                          ~BTRFS_INODE_##flag)
 #define btrfs_set_flag(inode, flag)     (BTRFS_I(inode)->flags |= \
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fba0478a95f4..fd0e0d80333b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2850,6 +2850,13 @@ out_fail:
         btrfs_throttle(root);
         return err;
 }
+static int btrfs_permission(struct inode *inode, int mask,
+                            struct nameidata *nd)
+{
+        if (btrfs_test_flag(inode, READONLY) && (mask & MAY_WRITE))
+                return -EACCES;
+        return generic_permission(inode, mask, NULL);
+}
 
 static struct inode_operations btrfs_dir_inode_operations = {
         .lookup         = btrfs_lookup,
@@ -2866,12 +2873,12 @@ static struct inode_operations btrfs_dir_inode_operations = {
         .getxattr       = generic_getxattr,
         .listxattr      = btrfs_listxattr,
         .removexattr    = generic_removexattr,
+        .permission     = btrfs_permission,
 };
-
 static struct inode_operations btrfs_dir_ro_inode_operations = {
         .lookup         = btrfs_lookup,
+        .permission     = btrfs_permission,
 };
-
 static struct file_operations btrfs_dir_file_operations = {
         .llseek         = generic_file_llseek,
         .read           = generic_read_dir,
@@ -2916,15 +2923,16 @@ static struct inode_operations btrfs_file_inode_operations = {
         .getxattr       = generic_getxattr,
         .listxattr      = btrfs_listxattr,
         .removexattr    = generic_removexattr,
+        .permission     = btrfs_permission,
 };
-
 static struct inode_operations btrfs_special_inode_operations = {
         .getattr        = btrfs_getattr,
         .setattr        = btrfs_setattr,
+        .permission     = btrfs_permission,
 };
-
 static struct inode_operations btrfs_symlink_inode_operations = {
         .readlink       = generic_readlink,
         .follow_link    = page_follow_link_light,
         .put_link       = page_put_link,
+        .permission     = btrfs_permission,
 };