From: Lorenzo Stoakes <lstoakes@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
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>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/10] mm: adjust get_user_pages* functions to explicitly pass FOLL_* flags
Date: Wed, 26 Oct 2016 09:55:47 +0100 [thread overview]
Message-ID: <20161026085547.GA3737@lucifer> (raw)
In-Reply-To: <20161018153050.GC13117@dhcp22.suse.cz>
On Tue, Oct 18, 2016 at 05:30:50PM +0200, Michal Hocko wrote:
>I am wondering whether we can go further. E.g. it is not really clear to
>me whether we need an explicit FOLL_REMOTE when we can in fact check
>mm != current->mm and imply that. Maybe there are some contexts which
>wouldn't work, I haven't checked.
>
>Then I am also wondering about FOLL_TOUCH behavior.
>__get_user_pages_unlocked has only few callers which used to be
>get_user_pages_unlocked before 1e9877902dc7e ("mm/gup: Introduce
>get_user_pages_remote()"). To me a dropped FOLL_TOUCH seems
>unintentional. Now that get_user_pages_unlocked has gup_flags argument I
>guess we might want to get rid of the __g-u-p-u version altogether, no?
>
>__get_user_pages is quite low level and imho shouldn't be exported. It's
>only user - kvm - should rather pull those two functions to gup instead
>and export them. There is nothing really KVM specific in them.
I believe I've attacked each of these, other than the use of explicit
FOLL_REMOTE which was explained by Dave.
> I also cannot say I would be entirely thrilled about get_user_pages_locked,
> we only have one user which can simply do lock g-u-p unlock AFAICS.
The principle difference here seems to be the availability of VM_FAULT_RETRY
behaviour (by passing a non-NULL locked argument), and indeed the comments in
gup.c recommends using get_user_pages_locked() if possible (though it seems not
to have been heeded too much :), so I'm not sure if this would be a fruitful
refactor, let me know!
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prev parent reply other threads:[~2016-10-26 8:55 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-13 0:20 Lorenzo Stoakes
2016-10-13 0:20 ` [PATCH 01/10] mm: remove write/force parameters from __get_user_pages_locked() Lorenzo Stoakes
2016-10-18 12:43 ` Jan Kara
2016-10-13 0:20 ` [PATCH 02/10] mm: remove write/force parameters from __get_user_pages_unlocked() Lorenzo Stoakes
2016-10-13 6:54 ` Paolo Bonzini
2016-10-18 12:46 ` Jan Kara
2016-10-13 0:20 ` [PATCH 03/10] mm: replace get_user_pages_unlocked() write/force parameters with gup_flags Lorenzo Stoakes
2016-10-18 12:50 ` Jan Kara
2016-10-13 0:20 ` [PATCH 04/10] mm: replace get_user_pages_locked() " Lorenzo Stoakes
2016-10-18 12:54 ` Jan Kara
2016-10-18 13:56 ` Lorenzo Stoakes
2016-10-19 7:32 ` Jan Kara
2016-10-19 7:33 ` Jan Kara
2016-10-13 0:20 ` [PATCH 05/10] mm: replace get_vaddr_frames() " Lorenzo Stoakes
2016-10-19 7:34 ` Jan Kara
2016-10-13 0:20 ` [PATCH 06/10] mm: replace get_user_pages() " Lorenzo Stoakes
2016-10-17 9:22 ` Jesper Nilsson
2016-10-19 7:44 ` Jan Kara
2016-10-13 0:20 ` [PATCH 07/10] mm: replace get_user_pages_remote() " Lorenzo Stoakes
2016-10-19 7:47 ` Jan Kara
2016-10-13 0:20 ` [PATCH 08/10] mm: replace __access_remote_vm() write parameter " Lorenzo Stoakes
2016-10-19 7:59 ` Jan Kara
2016-10-19 8:13 ` Michal Hocko
2016-10-19 8:40 ` Lorenzo Stoakes
2016-10-19 8:52 ` Michal Hocko
2016-10-19 9:06 ` Lorenzo Stoakes
2016-10-19 9:23 ` Michal Hocko
2016-10-13 0:20 ` [PATCH 09/10] mm: replace access_remote_vm() " Lorenzo Stoakes
2016-10-13 0:20 ` [PATCH 10/10] mm: replace access_process_vm() " Lorenzo Stoakes
2016-10-17 9:23 ` Jesper Nilsson
2016-10-19 11:10 ` Michael Ellerman
2016-10-13 7:32 ` [PATCH 00/10] mm: adjust get_user_pages* functions to explicitly pass FOLL_* flags Christian König
2016-10-18 15:30 ` Michal Hocko
2016-10-19 8:58 ` Lorenzo Stoakes
2016-10-19 9:07 ` Michal Hocko
2016-10-19 16:49 ` Dave Hansen
2016-10-19 17:01 ` Michal Hocko
2016-10-19 17:23 ` Dave Hansen
2016-10-20 19:26 ` Michal Hocko
2016-10-26 8:55 ` Lorenzo Stoakes [this message]
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