[PATCH] ubifs: Add freeze support

[Richard Weinberger]

Hyunchul,

Am 26.05.2017 um 01:30 schrieb Hyunchul Lee:
> From: Hyunchul Lee <cheol.lee at lge.com>
> 
> for un/freeze support, implement freeze_super and un/freeze_fs
> of super_operations.
> ubifs_freeze_super just calls freeze_super. because freeze_super always
> succeeds if file system is read-only,  UBIFS errors should be checked.
> if there are errors, UBIFS is switched to read-only mode.
> ubifs_freeze_fs runs commit if TNC/LPT isn't clean. though all writes
> are blocked and sync_fs is called before, if commit alreay was started
> before writes are blocked, TNC/LPT might have dirty COW nodes.

you explain how you implement that feature, but not why.
What is the use-case?
I always thought this interface is only being used by LVM.

Thanks,
//richard