Commit da24927b authored by Miao Xie's avatar Miao Xie Committed by Chris Mason
Browse files

Btrfs: get write access when removing a device 



Steps to reproduce:
 # mkfs.btrfs -d single -m single <disk0> <disk1>
 # mount -o ro <disk0> <mnt0>
 # mount -o ro <disk0> <mnt1>
 # mount -o remount,rw <mnt0>
 # umount <mnt0>
 # btrfs device delete <disk1> <mnt1>

We can remove a device from a R/O filesystem. The reason is that we just check
the R/O flag of the super block object. It is not enough, because the kernel
may set the R/O flag only for the mount point. We need invoke

	mnt_want_write_file()

to do a full check.

Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 198605a8

fs/btrfs/ioctl.c

+8 −4
Original line number Diff line number Diff line
@@ -2270,20 +2270,23 @@ out: 
	return ret;

}



static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)

static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)

{

	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;

	struct btrfs_ioctl_vol_args *vol_args;

	int ret;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



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

		return -EROFS;

	ret = mnt_want_write_file(file);

	if (ret)

		return ret;



	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,

			1)) {

		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");

		mnt_drop_write_file(file);

		return -EINPROGRESS;

	}
@@ -2300,6 +2303,7 @@ static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg) 
	kfree(vol_args);

out:

	mutex_unlock(&root->fs_info->volume_mutex);

	mnt_drop_write_file(file);

	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);

	return ret;

}
@@ -3842,7 +3846,7 @@ long btrfs_ioctl(struct file *file, unsigned int 
	case BTRFS_IOC_ADD_DEV:

		return btrfs_ioctl_add_dev(root, argp);

	case BTRFS_IOC_RM_DEV:

		return btrfs_ioctl_rm_dev(root, argp);

		return btrfs_ioctl_rm_dev(file, argp);

	case BTRFS_IOC_FS_INFO:

		return btrfs_ioctl_fs_info(root, argp);

	case BTRFS_IOC_DEV_INFO:

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