Re: [PATCH 1/1] mmap.c: find_vma: remove if(mm) check

On Wed, Mar 28, 2012 at 3:42 AM, Andrew Morton
[off-list ref] wrote:

On Mon, 26 Mar 2012 19:49:27 -0400
Kautuk Consul [off-list ref] wrote:

quoted

find_vma is called from kernel code where it is absolutely
sure that the mm_struct arg being passed to it is non-NULL.

Remove the if(mm) check.

It's odd that the if(mm) test exists - I wonder why it was originally
added.  My repo only goes back ten years, and it's there in 2.4.18.

Any code which calls find_vma() without an mm is surely pretty busted?


Still, I think I'd prefer to do

       if (WARN_ON_ONCE(!mm))
               return NULL;

yes, I agree. that is safe for now as there are a huge number of calls
to this API.

then let that bake for a kernel release, just to find out if we have a
weird caller out there, such as a function which is called by both user
threads and by kernel threads.

ok. I'll spin another one and send it to you with your suggestions in a day or
two when I go back home after my day job.

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