From: John Hubbard <jhubbard@nvidia.com>
To: Souptick Joarder <jrdr.linux@gmail.com>, <paulus@ozlabs.org>,
<mpe@ellerman.id.au>, <benh@kernel.crashing.org>,
<akpm@linux-foundation.org>, <peterz@infradead.org>,
<mingo@redhat.com>, <acme@kernel.org>, <mark.rutland@arm.com>,
<alexander.shishkin@linux.intel.com>, <jolsa@redhat.com>,
<namhyung@kernel.org>, <pbonzini@redhat.com>,
<sfr@canb.auug.org.au>, <rppt@linux.ibm.com>,
<aneesh.kumar@linux.ibm.com>, <msuchanek@suse.de>
Cc: <kvm-ppc@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<kvm@vger.kernel.org>, Matthew Wilcox <willy@infradead.org>
Subject: Re: [linux-next RFC v2] mm/gup.c: Convert to use get_user_{page|pages}_fast_only()
Date: Sun, 24 May 2020 18:06:55 -0700 [thread overview]
Message-ID: <c70dc7fa-352d-9f61-abb9-d578072978c9@nvidia.com> (raw)
In-Reply-To: <1590294434-19125-1-git-send-email-jrdr.linux@gmail.com>
On 2020-05-23 21:27, Souptick Joarder wrote:
> API __get_user_pages_fast() renamed to get_user_pages_fast_only()
> to align with pin_user_pages_fast_only().
>
> As part of this we will get rid of write parameter. Instead caller
> will pass FOLL_WRITE to get_user_pages_fast_only(). This will not
> change any existing functionality of the API.
>
> All the callers are changed to pass FOLL_WRITE.
This looks good. A few nits below, but with those fixed, feel free to
add:
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>
> There are few places where 1 is passed to 2nd parameter of
> __get_user_pages_fast() and return value is checked for 1
> like [1]. Those are replaced with new inline
> get_user_page_fast_only().
>
> [1] if (__get_user_pages_fast(hva, 1, 1, &page) == 1)
>
We try to avoid talking *too* much about the previous version of
the code. Just enough. So, instead of the above two paragraphs,
I'd compress it down to:
Also: introduce get_user_page_fast_only(), and use it in a few
places that hard-code nr_pages to 1.
...
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 93d93bd..8d4597f 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1817,10 +1817,16 @@ extern int mprotect_fixup(struct vm_area_struct *vma,
> /*
> * doesn't attempt to fault and will return short.
> */
> -int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> - struct page **pages);
> +int get_user_pages_fast_only(unsigned long start, int nr_pages,
> + unsigned int gup_flags, struct page **pages);
Silly nit:
Can you please leave the original indentation in place? I don't normally
comment about this, but I like the original indentation better, and it matches
the pin_user_pages_fast() below, too.
...
> @@ -2786,8 +2792,8 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
> * If the architecture does not support this function, simply return with no
> * pages pinned.
> */
> -int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> - struct page **pages)
> +int get_user_pages_fast_only(unsigned long start, int nr_pages,
> + unsigned int gup_flags, struct page **pages)
Same thing here: you've changed the original indentation, which was (arguably, but
to my mind anyway) more readable, and for no reason. It still would have fit within
80 cols.
I'm sure it's a perfect 50/50 mix of people who prefer either indentation style, and
so for brand new code, I'll remain silent, as long as it is consistent with either
itself and/or the surrounding code. But changing it back and forth is a bit
aggravating, and best avoided. :)
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2020-05-25 1:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-24 4:27 [linux-next RFC v2] mm/gup.c: Convert to use get_user_{page|pages}_fast_only() Souptick Joarder
2020-05-25 1:06 ` John Hubbard [this message]
2020-05-25 6:13 ` Souptick Joarder
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