Messages in this thread Patch in this message | | | Date | Mon, 23 Jun 2008 10:27:03 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [patch 2/5] Reinstate ZERO_PAGE optimization in get_user_pages() and fix XIP |
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On Tue, 24 Jun 2008, Jeff Chua wrote: > On Tue, Jun 24, 2008 at 12:39 AM, Linus Torvalds > <torvalds@linux-foundation.org> wrote: > > > > Jeff, does this still work with vmware? > > > No, this breaks vmware. Does this trace help?
Not really. I have no idea what vmware does, so any traces from vmware are pretty useless.
On the other hand, if you add a trace to the "use_zero_page()" function to print out the vm_flags and other details, that probably would help.
That said, since the previous patch _did_ work, I bet that one that does both VM_LOCKED and VM_SHARED works too. There was a reason I wanted to do that VM_SHARED test. I think the VM_SHARED test is sane, unlike the VM_LOCKED test (that is a fairly dubious hack for mlock).
So here's the final version. I bet it works.
Linus --- mm/memory.c | 23 +++++++++++++++++++++-- 1 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c index 9aefaae..423e0e7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1045,6 +1045,26 @@ 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) @@ -1119,8 +1139,7 @@ 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->fault)) + if (!write && use_zero_page(vma)) foll_flags |= FOLL_ANON; do {
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