Re: Regression: Requiring CAP_SYS_ADMIN for /proc/<pid>/pagemap causes application-level breakage
From: Linus Torvalds
Date: Wed Apr 29 2015 - 16:33:59 EST
On Wed, Apr 29, 2015 at 12:36 PM, Kirill A. Shutemov
> Emm.. I have hard time to understand how writable bit is enough to get
> soft-dirty-alike functionality.
I don't think it is.
For anonymous pages, maybe you can play tricks with comparing the page
'anon_vma' with the vma->anon_vma.
I haven't really thought that through, but does something like
static inline bool page_is_dirty_in_vma(struct page *page, struct
struct anon_vma *anon_vma = vma->anon_vma;
return page->mapping == (void *)anon_vma + PAGE_MAPPING_ANON;
end up working as a "page has been dirtied in this mapping"?
If the page came from another process and hasn't been written to, it
will have the anon_vma pointing to the originalting vma.
I may be high on some bad drugs, though. As mentioned, I didn't really
think this through.
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