On Thu, Apr 05, 2018 at 05:41:57PM +0800, Anand Jain wrote:
>
> > @@ -2716,6 +2718,7 @@ static long btrfs_ioctl_rm_dev(struct file *file,
> > void __user *arg)
> > ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> > goto out_drop_write;
> > }
> > + mutex_lock(&fs_info->volume_mutex);
> >
> > vol_args = memdup_user(arg, sizeof(*vol_args));
> > if (IS_ERR(vol_args)) { > @@ -2730,6 +2733,7 @@ static long
> > btrfs_ioctl_rm_dev(struct file
> *file, void __user *arg)
> > btrfs_info(fs_info, "disk deleted %s", vol_args->name);
> > kfree(vol_args);
> > out:
> > + mutex_unlock(&fs_info->volume_mutex);
> > clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
> > out_drop_write:
> > mnt_drop_write_file(file);
>
> Why not memdup_user() be outside of volume_mutex?
The point of the patch is to put the mutex_lock right next to the
exclusive operation bit setting. It's not optimal regarding the size of
critical section and normally the memdup should be outside.
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