From a68d2ebc1581a3aec57bd032651e013fa609f530 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@g5.osdl.org>
Date: Wed, 3 Aug 2005 10:07:09 -0700
Subject: [PATCH] Fix up recent get_user_pages() handling
The VM_FAULT_WRITE thing is an extra bit, not a valid return value, and
has to be treated as such by get_user_pages().
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
mm/memory.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 81d7117aa58b6..e046b7e4b5309 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -949,6 +949,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
cond_resched_lock(&mm->page_table_lock);
while (!(page = follow_page(mm, start, write_access))) {
+ int ret;
+
/*
* Shortcut for anonymous pages. We don't want
* to force the creation of pages tables for
@@ -961,16 +963,18 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
break;
}
spin_unlock(&mm->page_table_lock);
- switch (__handle_mm_fault(mm, vma, start,
- write_access)) {
- case VM_FAULT_WRITE:
- /*
- * do_wp_page has broken COW when
- * necessary, even if maybe_mkwrite
- * decided not to set pte_write
- */
+ ret = __handle_mm_fault(mm, vma, start, write_access);
+
+ /*
+ * The VM_FAULT_WRITE bit tells us that do_wp_page has
+ * broken COW when necessary, even if maybe_mkwrite
+ * decided not to set pte_write. We can thus safely do
+ * subsequent page lookups as if they were reads.
+ */
+ if (ret & VM_FAULT_WRITE)
write_access = 0;
- /* FALLTHRU */
+
+ switch (ret & ~VM_FAULT_WRITE) {
case VM_FAULT_MINOR:
tsk->min_flt++;
break;
--
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