linux-kernel - Re: [PATCH] mm: remove unnecessary __get_user_pages

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Message-ID: <20161026091542.GD18382@dhcp22.suse.cz>
Date:   Wed, 26 Oct 2016 11:15:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, Hugh Dickins <hughd@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Rik van Riel <riel@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls

On Wed 26-10-16 00:46:31, Lorenzo Stoakes wrote:
> The holdout for unexporting __get_user_pages_unlocked() is its invocation in
> mm/process_vm_access.c: process_vm_rw_single_vec(), as this definitely _does_
> seem to invoke VM_FAULT_RETRY behaviour which get_user_pages_remote() will not
> trigger if we were to replace it with the latter.

I am not sure I understand. Prior to 1e9877902dc7e this used
get_user_pages_unlocked. What prevents us from reintroducing it with
FOLL_REMOVE which was meant to be added by the above commit?

Or am I missing your point?
-- 
Michal Hocko
SUSE Labs