> -----Original Message-----
> From: Michael Tokarev [mailto:m...@tls.msk.ru]
> Sent: Wednesday, October 12, 2016 2:46 PM
> Subject: Re: [PATCH] mmap-alloc: check before use for ptr pointer
>
> 12.10.2016 05:05, Gonglei wrote:
> > If ptr mmap failed, we don't need to do a superfluous
> > calculation for offset variable by ptr (MAP_FAILED).
>
> What's the point? There's no problem in extra calculation
> if mmap failed, yes, but do we really care? As of it is now,
> it is more compact and readable, and works. I think.
>
I just think it's more reasonable because the ptr is checked after
used. Why do we need a extra calculation?
Regards,
-Gonglei
> Thanks,
>
> /mjt
>
> > Signed-off-by: Gonglei <arei.gong...@huawei.com>
> > ---
> > util/mmap-alloc.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
> > index 5a85aa3..577862b 100644
> > --- a/util/mmap-alloc.c
> > +++ b/util/mmap-alloc.c
> > @@ -61,13 +61,15 @@ void *qemu_ram_mmap(int fd, size_t size, size_t
> align, bool shared)
> > #else
> > void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS |
> MAP_PRIVATE, -1, 0);
> > #endif
> > - size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
> > + size_t offset;
> > void *ptr1;
> >
> > if (ptr == MAP_FAILED) {
> > return MAP_FAILED;
> > }
> >
> > + offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
> > +
> > /* Make sure align is a power of 2 */
> > assert(!(align & (align - 1)));
> > /* Always align to host page size */
> >
