Re: current->journal_info got nested! (was Re: [syzbot] [xfs?] [ext4?] general protection fault in jbd2__journal_start)

[Christoph Hellwig]

On Wed, Jan 31, 2024 at 05:02:25PM +1100, Dave Chinner wrote:
> This may not be true for other filesystems, but I don't think we
> can really say "page faults in any filesystem transaction are unsafe
> and should be banned"....

I think the point is page faults with current->journal_info set is
unsafe, as the can recurse into another file system using it.  If we
don't set current->journal_info (and your ideas for that sound sensible
to me), the question of page faults in transactions is decoupled from
that.  We just need to ensure we never recurse into a transaction in
the same or a dependent fs, which ot me suggest we'd better avoid it
if we easily can.