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authorLinus Torvalds <torvalds@linux-foundation.org>2008-06-23 11:21:37 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2008-06-24 14:08:31 -0700
commita3abcfa827d9bf769829d3ca0036a12a7a058a02 (patch)
parent31a26cd34a33c8137ebbf254e4e35536c45ae9b5 (diff)
Fix ZERO_PAGE breakage with vmware
commit 672ca28e300c17bf8d792a2a7a8631193e580c74 upstream Commit 89f5b7da2a6bad2e84670422ab8192382a5aeb9f ("Reinstate ZERO_PAGE optimization in 'get_user_pages()' and fix XIP") broke vmware, as reported by Jeff Chua: "This broke vmware 6.0.4. Jun 22 14:53:03.845: vmx| NOT_IMPLEMENTED /build/mts/release/bora-93057/bora/vmx/main/vmmonPosix.c:774" and the reason seems to be that there's an old bug in how we handle do FOLL_ANON on VM_SHARED areas in get_user_pages(), but since it only triggered if the whole page table was missing, nobody had apparently hit it before. The recent changes to 'follow_page()' made the FOLL_ANON logic trigger not just for whole missing page tables, but for individual pages as well, and exposed this problem. This fixes it by making the test for when FOLL_ANON is used more careful, and also makes the code easier to read and understand by moving the logic to a separate inline function. Reported-and-tested-by: Jeff Chua <jeff.chua.linux@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
1 files changed, 21 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index db6590c8cc11..df84668807ad 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,26 @@ no_page_table:
return page;
+/* Can we do the FOLL_ANON optimization? */
+static inline int use_zero_page(struct vm_area_struct *vma)
+ /*
+ * We don't want to optimize FOLL_ANON for make_pages_present()
+ * when it tries to page in a VM_LOCKED region. As to VM_SHARED,
+ * we want to get the page from the page tables to make sure
+ * that we serialize and update with any other user of that
+ * mapping.
+ */
+ if (vma->vm_flags & (VM_LOCKED | VM_SHARED))
+ return 0;
+ /*
+ * And if we have a fault or a nopfn routine, it's not an
+ * anonymous region.
+ */
+ return !vma->vm_ops ||
+ (!vma->vm_ops->fault && !vma->vm_ops->nopfn);
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, int len, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
@@ -1063,9 +1083,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
foll_flags = FOLL_TOUCH;
if (pages)
foll_flags |= FOLL_GET;
- if (!write && !(vma->vm_flags & VM_LOCKED) &&
- (!vma->vm_ops || (!vma->vm_ops->nopage &&
- !vma->vm_ops->fault)))
+ if (!write && use_zero_page(vma))
foll_flags |= FOLL_ANON;
do {