Re: [PATCH 6/6] libpager: Use libc heap for pagemap

[Samuel Thibault]

Sergey Bugaev, le ven. 07 mai 2021 12:26:39 +0300, a ecrit:
> On Thu, May 6, 2021 at 3:56 PM Sergey Bugaev <bugaevc@gmail.com> wrote:
> > -      newaddr = mmap (0, newsize * sizeof (*p->pagemap),
> > -                     PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
> > +      void *newaddr = reallocarray (p->pagemap, off,
> > +                                    sizeof (*p->pagemap));
> 
> It seems while fixing preexisting issues I accidentally introduces a
> new one. Unlike mmap, reallocarray does not zero-initialize the newly
> allocated memory; but other code expects new pagemap entries to be set
> to zero. This is the cause of those tarfs hangs I've been seeing
> lately.
> 
> I'm sorry, and here's a hotfix.

Applied, thanks!

> Sergey
> 
> -- >8 --
> Subject: [PATCH] libpager: Properly zero-initialize pagemap
> 
> Unlike mmap () and calloc (), reallocarray () does not automatically
> zero-fill the newly allocated memory. Do so explicitly.
> ---
>  libpager/pagemap.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/libpager/pagemap.c b/libpager/pagemap.c
> index 7bbb8c56..c7c86d60 100644
> --- a/libpager/pagemap.c
> +++ b/libpager/pagemap.c
> @@ -32,6 +32,8 @@ _pager_pagemap_resize (struct pager *p, vm_address_t off)
>        if (!newaddr)
>          return errno;
> 
> +      memset ((short *) newaddr + p->pagemapsize, 0,
> +              (off - p->pagemapsize) * sizeof (*p->pagemap));
>        p->pagemap = newaddr;
>        p->pagemapsize = off;
>      }
> -- 
> 2.31.1
>