Re: [bug report] mm: avoid leaving partial pfn mappings around in error case

[Dan Carpenter <dan.carpenter@linaro.org>]

On Sun, Sep 15, 2024 at 01:01:43PM +0100, Lorenzo Stoakes wrote:
> On Sun, Sep 15, 2024 at 01:08:27PM GMT, Dan Carpenter wrote:
> > Hi Linus,
> >
> > Commit 79a61cc3fc04 ("mm: avoid leaving partial pfn mappings around in
> > error case") from Sep 11, 2024 (linux-next), leads to the following
> > Smatch static checker warning:
> >
> > 	mm/memory.c:2709 remap_pfn_range_notrack()
> > 	warn: sleeping in atomic context
> >
> > mm/memory.c
> >     2696 int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
> >     2697                 unsigned long pfn, unsigned long size, pgprot_t prot)
> >     2698 {
> >     2699         int error = remap_pfn_range_internal(vma, addr, pfn, size, prot);
> >     2700
> >     2701         if (!error)
> >     2702                 return 0;
> >     2703
> >     2704         /*
> >     2705          * A partial pfn range mapping is dangerous: it does not
> >     2706          * maintain page reference counts, and callers may free
> >     2707          * pages due to the error. So zap it early.
> >     2708          */
> > --> 2709         zap_page_range_single(vma, addr, size, NULL);
> >
> > The lru_add_drain() function at the start of zap_page_range_single() takes a
> > mutext.
> 
> Hm does it? I see a local lock, and some folio batch locking which are
> local locks too?

Ah...  No it doesn't.  It's the mmu_notifier_invalidate_range_start() which is
a might_sleep() function.  Sorry for the confusion.

regards,
dan carpenter