Re: [PATCH v5] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared

[Kirill A. Shutemov]

On Tue, Aug 26, 2014 at 07:18:13PM +0400, Cyrill Gorcunov wrote:
> > Basically, it's safe if only soft-dirty is allowed to modify vm_flags
> > without down_write(). But why is soft-dirty so special?
> 
> because how we use this bit, i mean in normal workload this bit won't
> be used intensively i think so it's not widespread in kernel code

Weak argument to me.

What about walk through vmas twice: first with down_write() to modify
vm_flags and vm_page_prot, then downgrade_write() and do
walk_page_range() on every vma?

-- 
 Kirill A. Shutemov
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