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

Dave Hansen
2004-11-02T22:45:53Z

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Andrea Arcangeli wrote:
> Still I recommend investigating _why_ debug_pagealloc is violating the
> API. It might not be necessary to wait for the pageattr universal
> feature to make DEBUG_PAGEALLOC work safe.

This makes the DEBUG_PAGEALLOC stuff symmetric enough to boot for me,
and it's pretty damn simple. Any ideas for doing this without bloating
'struct page', even in the debugging case?

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---

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++;
}
_