netdev - Re: [PATCH 1/1] net/rds: Track user mapped pages through special API

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Date:   Wed, 12 Feb 2020 19:51:59 +0200
From:   Leon Romanovsky <leonro@...lanox.com>
To:     santosh.shilimkar@...cle.com
Cc:     John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hans Westgaard Ry <hans.westgaard.ry@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        rds-devel@....oracle.com, linux-rdma@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] net/rds: Track user mapped pages through special API

On Wed, Feb 12, 2020 at 09:31:51AM -0800, santosh.shilimkar@...cle.com wrote:
> On 2/11/20 7:03 PM, John Hubbard wrote:
> > From: Leon Romanovsky <leonro@...lanox.com>
> >
> > Convert net/rds to use the newly introduces pin_user_pages() API,
> > which properly sets FOLL_PIN. Setting FOLL_PIN is now required for
> > code that requires tracking of pinned pages.
> >
> > Note that this effectively changes the code's behavior: it now
> > ultimately calls set_page_dirty_lock(), instead of set_page_dirty().
> > This is probably more accurate.
> >
> > As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
> > dealing with a file backed page where we have reference on the inode it
> > hangs off." [1]
> >
> > [1] https://urldefense.com/v3/__https://lore.kernel.org/r/20190723153640.GB720@lst.de__;!!GqivPVa7Brio!OJHuecs9Iup5ig3kQBi_423uMMuskWhBQAdOICrY3UQ_ZfEaxt9ySY7E8y32Q7pk5tByyA$
> >
> > Cc: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
> > Cc: Santosh Shilimkar <santosh.shilimkar@...cle.com>
> > Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
> > Signed-off-by: John Hubbard <jhubbard@...dia.com>
> > ---
> Change looks fine to me. Just on safer side, we will try
> to test this change with regression suite to make sure it
> works as expected.

Thanks Santosh,
I wrote this patch before John's series was merged into the tree,
but back then, Hans tested it and it worked, hope that it still works. :)

>
> For patch itself,
>
> Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
>