Hi,

In a recent btrfs patch, it is going to add a mount option to disable 
log replay for btrfs, just like "norecovery" for ext4/xfs.

But in the discussion on the mount option name and use case, it seems 
better to have an unified and fs independent mount option alias for real 
RO mount

Reasons:
1) Some file system may have already used [no]"recovery" mount option
    In fact, btrfs has already used "recovery" mount option.
    Using "norecovery" mount option will be quite confusing for btrfs.

2) More straight forward mount option
    Currently, to get real RO mount, for ext4/xfs, user must use -o
    ro,norecovery.
    Just ro won't ensure real RO, and norecovery can't be used alone.
    If we have a simple alias, it would be much better for user to use.
    (it maybe done just in user space mount)

    Not to mention some fs (yeah, btrfs again) doesn't have "norecovery"
    but "nologreplay".

3) A lot of user even don't now mount ro can still modify device
    Yes, I didn't know this point until I checked the log replay code of
    btrfs.
    Adding such mount option alias may raise some attention of users.


Any ideas about this?

Thanks,
Qu