Re: [REGRESSION][BISECTED] Crash with Bad page state for FUSE/Flatpak related applications since v6.13

[Matthew Wilcox]

On Fri, Feb 07, 2025 at 04:22:56PM -0800, Joanne Koong wrote:
> > Thanks, Josef. I guess we can at least try to confirm we're on the right track.
> > Can anyone affected see if this (only compile tested) patch fixes the issue?
> > Created on top of 6.13.1.
> 
> This fixes the crash for me on 6.14.0-rc1. I ran the repro using
> Mantas's instructions for Obfuscate. I was able to trigger the crash
> on a clean build and then with this patch, I'm not seeing the crash
> anymore.

Since this patch fixes the bug, we're looking for one call to folio_put()
too many.  Is it possibly in fuse_try_move_page()?  In particular, this
one:

        /* Drop ref for ap->pages[] array */
        folio_put(oldfolio);

I don't know fuse very well.  Maybe this isn't it.