Re: [syzbot ci] Re: buffer: warn when a buffer is attached to a second mmb

[Aurelien DESBRIERES]

On Tue 27-10-26 13:10:55, Jan Kara wrote:
> Woohoo, great that we have added this. So now we have some filesystem bugs
> to analyze ;). At least in ext4 case this is a real bug as xattr blocks can
> be indeed shared among inodes.
[...]
> I'm not sure about the FAT cases because directory blocks where this
> triggers should better belong to a single directory. So it could be some
> race with freeing & reallocating blocks. Needs more digging.

Our mails crossed; forget the pr_warn alternative then, the WARN stays
as sent. If digging into the FAT cases from the syzbot repros helps, I
can take that on; say so and I will report what I find. Your free and
reallocate theory also describes something beamfs could do with its
indirect blocks, so I am running xfstests against the warning on our
side first.

Aurelien