Re: Criteria for mount messages. (was "Re: [PATCH] btrfs: remove skinny extent verbose message")

[Martin Steigerwald <martin@lichtvoll.de>]

Qu Wenruo - 24.06.22, 00:46:02 CEST:
> Thus my idea criteria would be:
> 
> - Would this feature bring bad impact to end users?
>    If the feature is only bringing good impact, it should not be
> output.
> 
>    Thus in this way, v2 cache nowadays should also be skipped, as it's
> already well tested, and no real disadvantage at all.

There is one aspect where I find those messages helpful:

To confirm that I successfully enabled a feature (like space cache v2).

However, for that there does not really need to be a kernel message on 
each mounting, as long as I have a way to confirm the currently used 
features of BTRFS like:

- which checksum algorithm?
- space cache v2
- big metadata
- which compression method configured as standard (I am aware that does 
not say anything about which files are compressed by which method)

and all other things like that.

Preferably in the output of just one command instead of being scattered 
around several different outputs or not even available at all. For 
example I am not aware of a command that confirms whether or not a 
filesystem uses "xxhash" instead of "crc32c" as checksum algorithm.

Something a bit similar to "tune2fs -l" or "xfs_info".

Is there such a something? I believe there is some way to dump a 
superblock however is there something that gives a structured output on 
what features are in use on a given filesystem?

Best,
-- 
Martin