Re: [PATCH] fstests: btrfs: make nospace_cache related test cases to work with latest v2 cache

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/11/5 18:25, Josef Bacik wrote:
> On Thu, Nov 04, 2021 at 08:55:53AM +0800, Qu Wenruo wrote:
>> In the coming btrfs-progs v5.15 release, mkfs.btrfs will change to use
>> v2 cache by default.
>>
>> However nospace_cache mount option will not work with v2 cache, as it
>> will make v2 cache out of sync with on-disk used space.
>>
>> So mounting a btrfs with v2 cache using "nospace_cache" will make btrfs
>> to reject the mount.
>>
>> There are quite some test cases relying on nospace_cache to prevent v1
>> cache to take up data space.
>>
>> For that case, we can append "clear_cache" mount option to it, so that
>> btrfs knows we do not only want to prevent cache from being created, but
>> also want to clear any existing v2 cache.
>>
>> By this, we can keep those existing tests to do the same behavior for
>> both v1 and v2 cache.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>
> This will re-generate the free space tree needlessly, and in fact won't be
> allowed for extent-tree-v2, so we'll just have to mess with it again.  Instead
> add a helper to get the options if they're needed, something like
>
> _btrfs_nocache_opt() {
> 	$BTRFS_UTIL_PROG inspect-internal $SCRATCH_DEV | grep FREE_SPACE_TREE
> 	if [ $? -eq 0 ]; then
> 		return "-o nospace_cache"
> 	fi
> 	return ""
> }

OK, this indeed sounds better.

Thanks,
Qu
>
> or something like that.  Thanks,
>
> Josef
>