On Thu, Aug 21, 2014 at 02:45:43AM +0300, Kirill A. Shutemov wrote: > On Wed, Aug 20, 2014 at 05:46:22PM -0400, Peter Feiner wrote: > It basically means VM_SOFTDIRTY require writenotify on the vma. > > What about patch below? Untested. And it seems it'll introduce bug similar > to bug fixed by c9d0bf241451, *but* IIUC we have it already in mprotect() > code path. > > I'll look more careful tomorrow. > > Not-signed-off-by: Kirill A. Shutemov <[email protected]> > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index dfc791c42d64..67d509a15969 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -851,8 +851,9 @@ static ssize_t clear_refs_write(struct file *file, const > char __user *buf, > if (type == CLEAR_REFS_MAPPED && !vma->vm_file) > continue; > if (type == CLEAR_REFS_SOFT_DIRTY) { > - if (vma->vm_flags & VM_SOFTDIRTY) > - vma->vm_flags &= ~VM_SOFTDIRTY; > + vma->vm_flags &= ~VM_SOFTDIRTY; > + vma->vm_page_prot = vm_get_page_prot( > + vma->vm_flags & ~VM_SHARED); > } > walk_page_range(vma->vm_start, vma->vm_end, > &clear_refs_walk); > -- > Kirill A. Shutemov
Thanks Kirill, I prefer your approach. I'll send a v2. I believe you're right about c9d0bf241451. It seems like passing the old & new pgprot through pgprot_modify would handle the problem. Furthermore, as you suggest, mprotect_fixup should use pgprot_modify when it turns write notification on. I think a patch like this is in order: Not-signed-off-by: Peter Feiner <[email protected]> diff --git a/mm/mmap.c b/mm/mmap.c index c1f2ea4..86f89a1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1611,18 +1611,15 @@ munmap_back: } if (vma_wants_writenotify(vma)) { - pgprot_t pprot = vma->vm_page_prot; - /* Can vma->vm_page_prot have changed?? * * Answer: Yes, drivers may have changed it in their * f_op->mmap method. * - * Ensures that vmas marked as uncached stay that way. + * Ensures that vmas marked with special bits stay that way. */ - vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED); - if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot))) - vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); + vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, + vm_get_page_prot(vm_flags & ~VM_SHARED); } vma_link(mm, vma, prev, rb_link, rb_parent); diff --git a/mm/mprotect.c b/mm/mprotect.c index c43d557..6826313 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -324,7 +324,8 @@ success: vm_get_page_prot(newflags)); if (vma_wants_writenotify(vma)) { - vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); + vma->vm_page_prot = pgprot_modify(vma->vm_page_prot, + vm_get_page_prot(newflags & ~VM_SHARED)); dirty_accountable = 1; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
