[PATCH] i386: fix vmalloc_sync_all() for Xen

From: Jan Beulich
Date: Wed Jun 18 2008 - 07:40:18 EST


Since the fourth PDPT entry cannot be shared under Xen,
vmalloc_sync_all() must iterate over pmd-s rather than pgd-s here.
Luckily, the code isn't used for native PAE (SHARED_KERNEL_PMD is 1)
and the change is benign to non-PAE.

Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

---
arch/x86/mm/fault.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)

--- linux-2.6.26-rc6/arch/x86/mm/fault.c 2008-06-18 09:56:16.000000000 +0200
+++ 2.6.26-rc6-i386-xen-vmalloc_sync_all/arch/x86/mm/fault.c 2008-06-06 08:51:52.000000000 +0200
@@ -921,32 +921,43 @@ void vmalloc_sync_all(void)
* start are only improving performance (without affecting correctness
* if undone).
*/
- static DECLARE_BITMAP(insync, PTRS_PER_PGD);
+#define sync_index(a) ((a) >> PMD_SHIFT)
+ static DECLARE_BITMAP(insync, PTRS_PER_PGD*PTRS_PER_PMD);
static unsigned long start = TASK_SIZE;
unsigned long address;

if (SHARED_KERNEL_PMD)
return;

- BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK);
- for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) {
- if (!test_bit(pgd_index(address), insync)) {
+ BUILD_BUG_ON(TASK_SIZE & ~PMD_MASK);
+ for (address = start; address >= TASK_SIZE; address += PMD_SIZE) {
+ if (!test_bit(sync_index(address), insync)) {
unsigned long flags;
struct page *page;

spin_lock_irqsave(&pgd_lock, flags);
+ if (unlikely(list_empty(&pgd_list))) {
+ spin_unlock_irqrestore(&pgd_lock, flags);
+ return;
+ }
list_for_each_entry(page, &pgd_list, lru) {
if (!vmalloc_sync_one(page_address(page),
- address))
+ address)) {
+ BUG_ON(list_first_entry(&pgd_list,
+ struct page,
+ lru) != page);
+ page = NULL;
break;
+ }
}
spin_unlock_irqrestore(&pgd_lock, flags);
- if (!page)
- set_bit(pgd_index(address), insync);
+ if (page)
+ set_bit(sync_index(address), insync);
}
- if (address == start && test_bit(pgd_index(address), insync))
- start = address + PGDIR_SIZE;
+ if (address == start && test_bit(sync_index(address), insync))
+ start = address + PMD_SIZE;
}
+#undef sync_index
#else /* CONFIG_X86_64 */
/*
* Note that races in the updates of insync and start aren't



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