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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: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Miao Xie 2012-11-26 08:44:50 +00:00 committed by Chris Mason
parent 198605a8e2
commit da24927b1e
1 changed files with 8 additions and 4 deletions
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12
fs/btrfs/ioctl.c
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@ -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: