linux-kernel - Re: [PATCH 1/2] mm: add locked parameter to get_user_pages

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Message-ID: <20161027105903.GI6454@dhcp22.suse.cz>
Date:   Thu, 27 Oct 2016 12:59:04 +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,
        linux-security-module@...r.kernel.org, linux-rdma@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: add locked parameter to get_user_pages_remote()

On Thu 27-10-16 12:55:27, Michal Hocko wrote:
> On Thu 27-10-16 10:51:40, Lorenzo Stoakes wrote:
> > This patch adds a int *locked parameter to get_user_pages_remote() to allow
> > VM_FAULT_RETRY faulting behaviour similar to get_user_pages_[un]locked().
> > 
> > Taking into account the previous adjustments to get_user_pages*() functions
> > allowing for the passing of gup_flags, we are now in a position where
> > __get_user_pages_unlocked() need only be exported for his ability to allow
> > VM_FAULT_RETRY behaviour, this adjustment allows us to subsequently unexport
> > __get_user_pages_unlocked() as well as allowing for future flexibility in the
> > use of get_user_pages_remote().
> 
> I would also add that this shouldn't introduce any functional change.

Forgot to mention that this also opens doors to change other g_u_p_r
callers to allow FAULT_RETRY logic.

-- 
Michal Hocko
SUSE Labs