linux-kernel - Re: [PATCH] mm/shmem: initialize folio to NULL

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Date:   Mon, 9 May 2022 15:53:56 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Tom Rix <trix@...hat.com>
Cc:     hughd@...gle.com, akpm@...ux-foundation.org, nathan@...nel.org,
        ndesaulniers@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] mm/shmem: initialize folio to NULL

On Mon, May 09, 2022 at 07:51:25AM -0700, Tom Rix wrote:
> 
> On 5/9/22 6:59 AM, Matthew Wilcox wrote:
> > On Mon, May 09, 2022 at 08:31:16AM -0400, Tom Rix wrote:
> > > The clang build fails with
> > > mm/shmem.c:1704:7: error: variable 'folio' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> > >    if (!page) {
> > >         ^~~~~
> > > The error handler for !page jumps to an if-check for an unset folio.
> > > So initialize folio to NULL.
> > I appreciate you're trying to help, but the fourth report of a problem
> > adds more noise than utility.
> > 
> > https://lore.kernel.org/linux-mm/?q=shmem+folio
> > 
> > shows emails about this from the cgelbot, Dan Carpenter, SeongJae Park,
> > Colin King, Nathan Chancellor and Sebastian Siewior.  So actually you
> > were seventh, not fourth.
> 
> From my point of view, the build has been broken for a week.

Yeah, shit happens when you're trying to fix patches and attend a
conference at the same time.

> It would be good if this and the other folio issue was fixed in linux-next
> soon.

As you can see, I sent a replacement patch series on the 4th which fixes
far more than the two problems you noticed.
https://lore.kernel.org/linux-mm/20220504182857.4013401-1-willy@infradead.org/

I can do no more than this.