diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-06-23 11:21:37 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2008-06-24 14:08:31 -0700 |
| commit | a3abcfa827d9bf769829d3ca0036a12a7a058a02 (patch) | |
| tree | 285235452ded60caa5d9b5152b7e3645f7461216 | |
| parent | 31a26cd34a33c8137ebbf254e4e35536c45ae9b5 (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>
| -rw-r--r-- | mm/memory.c | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c index db6590c8cc1..df84668807a 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 { |