linux-kernel - Re: [PATCH v6 12/14] mm/gup: longterm pin migration cleaup

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Message-ID: <20210120131937.GG4605@ziepe.ca>
Date:   Wed, 20 Jan 2021 09:19:37 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, vbabka@...e.cz, mhocko@...e.com,
        david@...hat.com, osalvador@...e.de, dan.j.williams@...el.com,
        sashal@...nel.org, tyhicks@...ux.microsoft.com,
        iamjoonsoo.kim@....com, mike.kravetz@...cle.com,
        rostedt@...dmis.org, mingo@...hat.com, peterz@...radead.org,
        mgorman@...e.de, willy@...radead.org, rientjes@...gle.com,
        jhubbard@...dia.com, linux-doc@...r.kernel.org,
        ira.weiny@...el.com, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v6 12/14] mm/gup: longterm pin migration cleaup

On Tue, Jan 19, 2021 at 08:43:31PM -0500, Pavel Tatashin wrote:
> When pages are longterm pinned, we must migrated them out of movable zone.
> The function that migrates them has a hidden loop with goto. The loop is
> to retry on isolation failures, and after successful migration.
> 
> Make this code better by moving this loop to the caller.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
>  mm/gup.c | 88 +++++++++++++++++++++++---------------------------------
>  1 file changed, 36 insertions(+), 52 deletions(-)

This looks OK, it is better

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

I really dislike we always have to go over the page list twice in pin
mode

The is_pinnable_page() and LRU isolation should really be done inside
__get_user_pages_locked() as each page is added to the output list

But that is more of a larger issue than this series

Jason