linux-kernel - Re: fuse: kernel BUG at mm/truncate.c:763!

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Message-ID: <YFNEjnjF+RujYOL0@suse.de>
Date:   Thu, 18 Mar 2021 12:16:14 +0000
From:   Luis Henriques <lhenriques@...e.de>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm <linux-mm@...ck.org>
Subject: Re: fuse: kernel BUG at mm/truncate.c:763!

On Thu, Mar 18, 2021 at 11:55:43AM +0000, Matthew Wilcox wrote:
> On Thu, Mar 18, 2021 at 11:29:28AM +0000, Luis Henriques wrote:
> > On Thu, Mar 18, 2021 at 02:03:02PM +0300, Kirill A. Shutemov wrote:
> > > On Thu, Mar 18, 2021 at 11:59:59AM +0100, Miklos Szeredi wrote:
> > > > > [16247.536348] page:00000000dfe36ab1 refcount:673 mapcount:0 mapping:00000000f982a7f8 index:0x1400 pfn:0x4c65e00
> > > > > [16247.536359] head:00000000dfe36ab1 order:9 compound_mapcount:0 compound_pincount:0
> > > > 
> > > > This is a compound page alright.   Have no idea how it got into fuse's
> > > > pagecache.
> > > 
> > > 
> > > Luis, do you have CONFIG_READ_ONLY_THP_FOR_FS enabled?
> > 
> > Yes, it looks like Tumbleweed kernels have that config option enabled by
> > default.  And it this feature was introduced in 5.4 (the bug doesn't seem
> > to be reproducible in 5.3).
> 
> Can you try adding this patch?
> 
> https://git.infradead.org/users/willy/pagecache.git/commitdiff/369a4fcd78369b7a026bdef465af9669bde98ef4

Yep, sure.  Unfortunately, the testing round-trip can be a bit high.  I'll
push a new kernel build and ask the reporter to give it a try.

[ I'll add this patch on top of the s/BUG_ON/VM_BUG_ON_PAGE change. ]

Cheers,
--
Luís