From: John Hubbard <jhubbard@nvidia.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>,
<linux-next@vger.kernel.org>, <akpm@linux-foundation.org>
Cc: <borntraeger@de.ibm.com>, <david@redhat.com>,
<aarcange@redhat.com>, <linux-mm@kvack.org>,
<frankja@linux.ibm.com>, <sfr@canb.auug.org.au>,
<linux-kernel@vger.kernel.org>, <linux-s390@vger.kernel.org>,
Jan Kara <jack@suse.cz>,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [RFC v1 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL_PIN pages"
Date: Fri, 28 Feb 2020 15:08:35 -0800 [thread overview]
Message-ID: <c98038da-cf52-27f5-1aed-b69287a5dec0@nvidia.com> (raw)
In-Reply-To: <20200228154322.329228-3-imbrenda@linux.ibm.com>
On 2/28/20 7:43 AM, Claudio Imbrenda wrote:
> In case pin fails, we need to unpin, a simple put_page will not be enough
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> mm/gup.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index f589299b0d4a..0b9a806898f3 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2134,7 +2134,10 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
> goto pte_unmap;
>
> if (unlikely(pte_val(pte) != pte_val(*ptep))) {
> - put_page(head);
> + if (flags & FOLL_GET)
> + put_page(head);
> + else if (flags & FOLL_PIN)
> + unpin_user_page(head);
Hi Claudio,
Instead, I think that should actually be:
put_compound_head(page, 1, flags);
which does a bit more (bug checks and /proc/vmstat instrumentation) than your diff,
but has the same basic idea: call the right "put" function.
...oh, actually, I see you have the commit hash in the subject line. Instead, it should
be in the commit description. Let's maybe change the subject line to approx:
mm/gup: Fix a missing put_compound_head() call in gup_pte_range()
And the write up...how about something like this, if you like it:
try_grab_compound_head() must be undone via put_compound_head(), not put_page().
This was missed in the original implementation of the gup/dma tracking patch, so
fix it now.
Fixes: 0ea2781c3de4 ("mm/gup: track FOLL_PIN pages")
(Aside: I'm using the linux-next commit hash. How does one get the correct hash before
it goes to mainline? I guess maintainer scripts fix all those up?)
It's also good to Cc some reviewers in case I'm overlooking something, so I'm adding
Jan and Kirill.
thanks,
--
John Hubbard
NVIDIA
> goto pte_unmap;
> }
>
>
next prev parent reply other threads:[~2020-02-28 23:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 15:43 [RFC v1 0/2] add callbacks for inaccessible pages Claudio Imbrenda
2020-02-28 15:43 ` [RFC v1 1/2] fixup for 9947ea2c1e608e32669d5caeb67b3e3fba3309e8 "mm/gup: track FOLL_PIN pages" Claudio Imbrenda
2020-02-28 15:45 ` Claudio Imbrenda
2020-02-28 15:43 ` [RFC v1 1/2] mm/gup: fixup for 9947ea2c1e608e32 " Claudio Imbrenda
2020-02-28 23:08 ` John Hubbard [this message]
2020-02-29 10:51 ` Claudio Imbrenda
2020-02-29 20:09 ` John Hubbard
2020-03-02 13:46 ` Michal Hocko
2020-02-28 15:43 ` [RFC v1 2/2] mm/gup/writeback: add callbacks for inaccessible pages Claudio Imbrenda
2020-02-28 16:08 ` Christian Borntraeger
2020-02-29 0:08 ` John Hubbard
2020-02-29 10:49 ` Claudio Imbrenda
2020-02-29 20:07 ` John Hubbard
2020-03-01 3:47 ` Andrew Morton
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