Re: fix iounmap and a pageattr memleak (x86 and x86-64)

[Dave Hansen]

Hi Andrea,

Are you sure that BUG_ON() should be for !page_count(kpte_page)?  I
noticed that I was getting some BUGs when the count went back to 0, but
the pte page was completely full with valid ptes.  I *think* it's
correct to make it:

       BUG_ON(page_count(kpte_page) < 0);

Or, I guess we could keep the old BUG_ON(), and put it inside the else
block with the __put_page().  

-- Dave


---

 memhotplug1-dave/arch/i386/mm/pageattr.c |    7 +++++--
 memhotplug1-dave/include/linux/mm.h      |    3 +++
 memhotplug1-dave/mm/page_alloc.c         |    5 ++++-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff -puN include/linux/mm.h~Z3-page_debugging include/linux/mm.h
--- memhotplug1/include/linux/mm.h~Z3-page_debugging	2004-11-02 14:29:51.000000000 -0800
+++ memhotplug1-dave/include/linux/mm.h	2004-11-02 14:37:08.000000000 -0800
@@ -245,6 +245,9 @@ struct page {
 	void *virtual;			/* Kernel virtual address (NULL if
 					   not kmapped, ie. highmem) */
 #endif /* WANT_PAGE_VIRTUAL */
+#ifdef CONFIG_DEBUG_PAGEALLOC
+	int mapped;
+#endif
 };
 
 #ifdef CONFIG_MEMORY_HOTPLUG
diff -puN arch/i386/mm/pageattr.c~Z3-page_debugging arch/i386/mm/pageattr.c
--- memhotplug1/arch/i386/mm/pageattr.c~Z3-page_debugging	2004-11-02 14:31:07.000000000 -0800
+++ memhotplug1-dave/arch/i386/mm/pageattr.c	2004-11-02 14:41:00.000000000 -0800
@@ -153,7 +153,7 @@ __change_page_attr(struct page *page, pg
 		printk("pgprot_val(PAGE_KERNEL): %08lx\n", pgprot_val(PAGE_KERNEL));
 		printk("(pte_val(*kpte) & _PAGE_PSE): %08lx\n", (pte_val(*kpte) & _PAGE_PSE)); 
 		printk("path: %d\n", path);
-		BUG();
+		WARN_ON(1);
 	}
 
 	if (cpu_has_pse && (page_count(kpte_page) == 1)) {
@@ -224,7 +224,10 @@ void kernel_map_pages(struct page *page,
 	/* the return value is ignored - the calls cannot fail,
 	 * large pages are disabled at boot time.
 	 */
-	change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
+	if (enable && !page->mapped)
+		change_page_attr(page, numpages, PAGE_KERNEL);
+	else if (!enable && page->mapped)
+		change_page_attr(page, numpages, __pgprot(0));
 	/* we should perform an IPI and flush all tlbs,
 	 * but that can deadlock->flush only current cpu.
 	 */
diff -puN mm/page_alloc.c~Z3-page_debugging mm/page_alloc.c
--- memhotplug1/mm/page_alloc.c~Z3-page_debugging	2004-11-02 14:37:53.000000000 -0800
+++ memhotplug1-dave/mm/page_alloc.c	2004-11-02 14:42:56.000000000 -0800
@@ -1840,8 +1840,11 @@ void __devinit memmap_init_zone(unsigned
 		INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
 		/* The shift won't overflow because ZONE_NORMAL is below 4G. */
-		if (!is_highmem_idx(zone))
+		if (!is_highmem_idx(zone)) {
 			set_page_address(page, __va(start_pfn << PAGE_SHIFT));
+			page->mapped = 1;
+		} else
+			page->mapped = 0;
 #endif
 		start_pfn++;
 	}
_