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/ctree.h b/fs/btrfs/ctree.h
index af52f6d..4403e56 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -597,6 +597,8 @@
u8 type;
} __attribute__ ((__packed__));
+#define BTRFS_ROOT_SUBVOL_RDONLY (1ULL << 0)
+
struct btrfs_root_item {
struct btrfs_inode_item inode;
__le64 generation;
@@ -1893,6 +1895,11 @@
BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct btrfs_root_item,
last_snapshot, 64);
+static inline bool btrfs_root_readonly(struct btrfs_root *root)
+{
+ return root->root_item.flags & BTRFS_ROOT_SUBVOL_RDONLY;
+}
+
/* struct btrfs_super_block */
BTRFS_SETGET_STACK_FUNCS(super_bytenr, struct btrfs_super_block, bytenr, 64);