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/inode.c b/fs/btrfs/inode.c
index 5f91944..956f1eb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3671,8 +3671,12 @@
static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
int err;
+ if (btrfs_root_readonly(root))
+ return -EROFS;
+
err = inode_change_ok(inode, attr);
if (err)
return err;
@@ -7206,6 +7210,10 @@
static int btrfs_permission(struct inode *inode, int mask)
{
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+
+ if (btrfs_root_readonly(root) && (mask & MAY_WRITE))
+ return -EROFS;
if ((BTRFS_I(inode)->flags & BTRFS_INODE_READONLY) && (mask & MAY_WRITE))
return -EACCES;
return generic_permission(inode, mask, btrfs_check_acl);