From: Michal Hocko <mhocko@kernel.org>
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: linux-mm@kvack.org,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Jan Kara" <jack@suse.cz>, "Hugh Dickins" <hughd@google.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Rik van Riel" <riel@redhat.com>,
"Mel Gorman" <mgorman@techsingularity.net>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls
Date: Wed, 26 Oct 2016 11:07:05 +0200 [thread overview]
Message-ID: <20161026090705.GA18382@dhcp22.suse.cz> (raw)
In-Reply-To: <20161026075952.GA30977@lucifer>
On Wed 26-10-16 08:59:52, Lorenzo Stoakes wrote:
> On Wed, Oct 26, 2016 at 12:36:09AM +0100, Lorenzo Stoakes wrote:
> > In hva_to_pfn_slow() we are able to replace __get_user_pages_unlocked() with
> > get_user_pages_unlocked() since we can now pass gup_flags.
> >
> > In async_pf_execute() we need to pass different tsk, mm arguments so
> > get_user_pages_remote() is the sane replacement here (having added manual
> > acquisition and release of mmap_sem.)
> >
> > Since we pass a NULL pages parameter the subsequent call to
> > __get_user_pages_locked() will have previously bailed any attempt at
> > VM_FAULT_RETRY, so we do not change this behaviour by using
> > get_user_pages_remote() which does not invoke VM_FAULT_RETRY logic at all.
> >
> > Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
>
> Note that the use of get_user_pages_remote() in async_pf_execute() reintroduces
> the use of the FOLL_TOUCH flag - I don't think this is a problem as this flag
> was dropped by 1e987790 ("mm/gup: Introduce get_user_pages_remote()") which
> states 'Without protection keys, this patch should not change any behavior', so
> I don't think this was intentional.
Yes, I have already mentioned this in one of my previous emails. This
indeed doesn't seem to be intentional
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-10-26 9:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 23:36 [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes
2016-10-25 23:46 ` Lorenzo Stoakes
2016-10-26 9:15 ` Michal Hocko
2016-10-26 9:39 ` Lorenzo Stoakes
2016-10-26 9:54 ` Michal Hocko
2016-10-26 7:59 ` Lorenzo Stoakes
2016-10-26 9:07 ` Michal Hocko [this message]
2016-10-26 9:12 ` Michal Hocko
2016-10-26 9:25 ` [PATCH v2] " Lorenzo Stoakes
2016-10-27 0:12 ` Andrew Morton
2016-10-27 7:06 ` Lorenzo Stoakes
2016-10-27 9:27 ` Paolo Bonzini
2016-10-27 9:32 ` Lorenzo Stoakes
2016-10-27 9:35 ` Paolo Bonzini
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