Re: [PATCH 2/2] mm: add a field to store names for private anonymous memory

[Colin Cross <ccross@android.com>]

On Thu, Jul 11, 2013 at 11:36 PM, Dave Hansen <dave.hansen@intel.com> wrote:
> On 07/11/2013 07:34 PM, Colin Cross wrote:
>> +             pages_pinned = get_user_pages(current, mm, page_start_vaddr,
>> +                             1, 0, 0, &page, NULL);
>> +             if (pages_pinned < 1) {
>> +                     seq_puts(m, "<fault>]");
>> +                     return;
>> +             }
>> +
>> +             kaddr = (const char *)kmap(page);
>> +             len = min(max_len, PAGE_SIZE - page_offset);
>> +             write_len = strnlen(kaddr + page_offset, len);
>> +             seq_write(m, kaddr + page_offset, write_len);
>> +             kunmap(page);
>> +             put_page(page);
>
> This looks a bit like access_process_vm()?  Can you perhaps use it here?

It's a lot like __access_remote_vm, and this pattern is repeated in
many other places in the kernel.  I didn't try to reuse any of them
because I wanted to stop reading at a null byte and __access_remote_vm
would read the full NAME_MAX every time.  I was also avoiding having
to allocate a NAME_MAX sized buffer to copy into, instead passing the
mapped user page directly to seq_write.

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