Re: [patch 2.6.13-rc4] fix get_user_pages bug

[Linus Torvalds]

On Tue, 2 Aug 2005, Martin Schwidefsky wrote:
> 
> Why do we require the !pte_dirty(pte) check? I don't get it. If a writeable
> clean pte is just fine then why do we check the dirty bit at all? Doesn't
> pte_dirty() imply pte_write()?

A _non_writable and clean pty is _also_ fine sometimes. But only if we 
have broken COW and marked it dirty.

> With the additional !pte_write(pte) check (and if I haven't overlooked
> something which is not unlikely) s390 should work fine even without the
> software-dirty bit hack.

No it won't. It will just loop forever in a tight loop if somebody tries 
to put a breakpoint on a read-only location.

On the other hand, this being s390, maybe nobody cares?

		Linus
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