commit bab70a4af737f623de5b034976a311055308ab86
author Eugene Surovegin <ebs@ebshome.net> Tue Mar 28 10:13:12 2006 -0800
committer Paul Mackerras <paulus@samba.org> Wed Mar 29 13:44:15 2006 +1100
tree f8c0e9463de01323db2cb1a62f4eb83adb5ce7ca
parent bac30d1a78d0f11c613968fc8b351a91ed465386

[PATCH] lock PTE before updating it in 440/BookE page fault handler

Fix 44x and BookE page fault handler to correctly lock PTE before
trying to pte_update() it, otherwise this PTE might be swapped out
after pte_present() check but before pte_uptdate() call, resulting in
corrupted PTE. This can happen with enabled preemption and low memory
condition.

Signed-off-by: Eugene Surovegin <ebs@ebshome.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/pgtable_32.c

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index d296eb6..9062860 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -372,7 +372,7 @@
  * the PTE pointer is unmodified if PTE is not found.
  */
 int
-get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep)
+get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
 {
         pgd_t	*pgd;
         pmd_t	*pmd;
@@ -387,6 +387,8 @@
                         if (pte) {
 				retval = 1;
 				*ptep = pte;
+				if (pmdp)
+					*pmdp = pmd;
 				/* XXX caller needs to do pte_unmap, yuck */
                         }
                 }
@@ -424,7 +426,7 @@
 		mm = &init_mm;
 
 	pa = 0;
-	if (get_pteptr(mm, addr, &pte)) {
+	if (get_pteptr(mm, addr, &pte, NULL)) {
 		pa = (pte_val(*pte) & PAGE_MASK) | (addr & ~PAGE_MASK);
 		pte_unmap(pte);
 	}