Comment # 12 on bug 1231836 from Fabian Vogt

(In reply to Wenruo Qu from comment #10)
> (In reply to Wenruo Qu from comment #9)
> > BTW, I also explored another solution, to allow mismatch in sb->s_flags and
> > fc->sb_flags, then reconfigure.
> > This methods avoid the brute force retry loop, and use proper rwsem to
> > prevent race in theory.
> > 
> > But it just doesn't work.
> > 
> > If the fs is initially mounted RO, a new RW open on the same device will
> > return -EINVAL, thus rejecting the mount way earlier before we can get a
> > proper super block to continue.
> > 
> > That's why we're risking the race by retry without a proper sb lock to hold.
> 
> What an idiot I am, I'm using a wrong script to test, thus mounting a wrong
> device, no wonder device scan failed, it's not related to the flag.

I've done even more stupid stuff, don't worry!

> I'll do more testing to make sure if we can go the new solution.

FWICT the latest patch on the btrfs ML upstream looks like it would be ok to
merge. Can we get this in TW and SLM 6.x?