Btrfs: Add readonly snapshots support
Usage:
Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and call
ioctl(BTRFS_I0CTL_SNAP_CREATE_V2).
Implementation:
- Set readonly bit of btrfs_root_item->flags.
- Add readonly checks in btrfs_permission (inode_permission),
btrfs_setattr, btrfs_set/remove_xattr and some ioctls.
Changelog for v3:
- Eliminate btrfs_root->readonly, but check btrfs_root->root_item.flags.
- Rename BTRFS_ROOT_SNAP_RDONLY to BTRFS_ROOT_SUBVOL_RDONLY.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 698fdd2..a577653 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -316,6 +316,15 @@
int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags)
{
+ struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+
+ /*
+ * The permission on security.* and system.* is not checked
+ * in permission().
+ */
+ if (btrfs_root_readonly(root))
+ return -EROFS;
+
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler
@@ -336,6 +345,15 @@
int btrfs_removexattr(struct dentry *dentry, const char *name)
{
+ struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+
+ /*
+ * The permission on security.* and system.* is not checked
+ * in permission().
+ */
+ if (btrfs_root_readonly(root))
+ return -EROFS;
+
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler