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Commit 0caa102d authored by Li Zefan's avatar Li Zefan
Browse files

Btrfs: Add BTRFS_IOC_SUBVOL_GETFLAGS/SETFLAGS ioctls 



This allows us to set a snapshot or a subvolume readonly or writable
on the fly.

Usage:

Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and then
call ioctl(BTRFS_IOCTL_SUBVOL_SETFLAGS);

Changelog for v3:

- Change to pass __u64 as ioctl parameter.

Changelog for v2:

- Add _GETFLAGS ioctl.
- Check if the passed fd is the root of a subvolume.
- Change the name from _SNAP_SETFLAGS to _SUBVOL_SETFLAGS.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
parent b83cc969

fs/btrfs/ioctl.c

+83 −0
Original line number Diff line number Diff line
@@ -1009,6 +1009,85 @@ out: 
	return ret;

}



static noinline int btrfs_ioctl_subvol_getflags(struct file *file,

						void __user *arg)

{

	struct inode *inode = fdentry(file)->d_inode;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	int ret = 0;

	u64 flags = 0;



	if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)

		return -EINVAL;



	down_read(&root->fs_info->subvol_sem);

	if (btrfs_root_readonly(root))

		flags |= BTRFS_SUBVOL_RDONLY;

	up_read(&root->fs_info->subvol_sem);



	if (copy_to_user(arg, &flags, sizeof(flags)))

		ret = -EFAULT;



	return ret;

}



static noinline int btrfs_ioctl_subvol_setflags(struct file *file,

					      void __user *arg)

{

	struct inode *inode = fdentry(file)->d_inode;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	struct btrfs_trans_handle *trans;

	u64 root_flags;

	u64 flags;

	int ret = 0;



	if (root->fs_info->sb->s_flags & MS_RDONLY)

		return -EROFS;



	if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)

		return -EINVAL;



	if (copy_from_user(&flags, arg, sizeof(flags)))

		return -EFAULT;



	if (flags & ~BTRFS_SUBVOL_CREATE_ASYNC)

		return -EINVAL;



	if (flags & ~BTRFS_SUBVOL_RDONLY)

		return -EOPNOTSUPP;



	down_write(&root->fs_info->subvol_sem);



	/* nothing to do */

	if (!!(flags & BTRFS_SUBVOL_RDONLY) == btrfs_root_readonly(root))

		goto out;



	root_flags = btrfs_root_flags(&root->root_item);

	if (flags & BTRFS_SUBVOL_RDONLY)

		btrfs_set_root_flags(&root->root_item,

				     root_flags | BTRFS_ROOT_SUBVOL_RDONLY);

	else

		btrfs_set_root_flags(&root->root_item,

				     root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);



	trans = btrfs_start_transaction(root, 1);

	if (IS_ERR(trans)) {

		ret = PTR_ERR(trans);

		goto out_reset;

	}



	ret = btrfs_update_root(trans, root,

				&root->root_key, &root->root_item);



	btrfs_commit_transaction(trans, root);

out_reset:

	if (ret)

		btrfs_set_root_flags(&root->root_item, root_flags);

out:

	up_write(&root->fs_info->subvol_sem);

	return ret;

}



/*

 * helper to check if the subvolume references other subvolumes

 */
@@ -2282,6 +2361,10 @@ long btrfs_ioctl(struct file *file, unsigned int 
		return btrfs_ioctl_snap_create(file, argp, 1);

	case BTRFS_IOC_SNAP_DESTROY:

		return btrfs_ioctl_snap_destroy(file, argp);

	case BTRFS_IOC_SUBVOL_GETFLAGS:

		return btrfs_ioctl_subvol_getflags(file, argp);

	case BTRFS_IOC_SUBVOL_SETFLAGS:

		return btrfs_ioctl_subvol_setflags(file, argp);

	case BTRFS_IOC_DEFAULT_SUBVOL:

		return btrfs_ioctl_default_subvol(file, argp);

	case BTRFS_IOC_DEFRAG:

fs/btrfs/ioctl.h

+2 −0
Original line number Diff line number Diff line
@@ -194,4 +194,6 @@ struct btrfs_ioctl_space_args { 
#define BTRFS_IOC_WAIT_SYNC  _IOW(BTRFS_IOCTL_MAGIC, 22, __u64)

#define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \

				   struct btrfs_ioctl_vol_args_v2)

#define BTRFS_IOC_SUBVOL_GETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 25, __u64)

#define BTRFS_IOC_SUBVOL_SETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 26, __u64)

#endif