lkml.org 
[lkml]   [2013]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff()
On Sun, 14 Jul 2013 18:54:51 +0200 Oleg Nesterov <oleg@redhat.com> wrote:

> mmap() doesn't allow the non-anonymous mappings with VM_GROWS* bit set.
> In particular this means that mmap_region()->vma_merge(file, vm_flags)
> must always fail if vm_flags & VM_GROWS. So it does not make sense to
> check VM_GROWS* after we already allocated the new vma, the only caller,
> do_mmap_pgoff(), which can pass this flag can do the check itself.
>
> And this looks a bit more correct, mmap_region() already unmapped the
> old mapping at this stage. But if mmap() is going to fail, it should
> avoid do_munmap() if possible.
>
> ...
>
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1327,6 +1327,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
> }
> }
>
> + /* Only MAP_PRIVATE|MAP_ANONYMOUS can use MAP_GROWS */
> + if ((vm_flags & VM_MAYSHARE) && (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)))

That is of course vm_flags&(VM_MAYSHARE|VM_GROWSDOWN|VM_GROWSUP), but
that perhaps is less clear.

> + return -EINVAL;

I had to stare for a while but yes, the change looks OK to me.


\
 
 \ /
  Last update: 2013-07-17 00:21    [W:0.067 / U:2.796 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site