do_wp_page

["Raghu R. Arur" <rra2002@aria.ncl.cs.columbia.edu>]

 hi,

  In do_wp_page of 2.4.19 why is the rss value of  address space
incremented only when the old_page ( the page on which the process faults
due to write protection) is a reserved page. I mean if the process has
mapped a read only page ( which is different from a ZERO_PAGE) and if it
faults on that page when it tries to
write, the rss value is not incremented even if a new page is created
and page table entry is set to the allocated page. What am i missing here?

	new_page = alloc_page(GFP_HIGHUSER);
	if (!new_page)
		goto no_mem;
	copy_cow_page(old_page,new_page,address);
	/*
	 * Re-check the pte - we dropped the lock
	 */
	spin_lock(&mm->page_table_lock);
	if (pte_same(*page_table, pte)) {
	  if (PageReserved(old_page)) {
			++mm->rss;
	  }
		break_cow(vma, new_page, address, page_table);
		lru_cache_add(new_page);
		/* Free the old page.. */
		new_page = old_page;
	}

 thanks,
Raghu
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