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Date:   Mon, 9 Oct 2023 19:19:22 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Lorenzo Stoakes <lstoakes@gmail.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Richard Cochran <richardcochran@gmail.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH 2/4] mm/gup: explicitly define and check internal GUP
 flags, disallow FOLL_TOUCH
Message-ID: <20231009221922.GC3952@nvidia.com>
References: <cover.1696174961.git.lstoakes@gmail.com>
 <5b20f3cda7cd841555c2626f98d23aa25a039828.1696174961.git.lstoakes@gmail.com>
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On Sun, Oct 01, 2023 at 05:00:03PM +0100, Lorenzo Stoakes wrote:
> Rather than open-coding a list of internal GUP flags in
> is_valid_gup_args(), define which ones are internal.
> 
> In addition, we were not explicitly checking to see if the user passed in
> FOLL_TOUCH somehow, this patch fixes that.
> 
> Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
> ---
>  mm/gup.c      | 5 ++---
>  mm/internal.h | 3 +++
>  2 files changed, 5 insertions(+), 3 deletions(-)

Does gup_test still work? It uses FOLL_TOUCH?

Hmm. I guess it was broken for a while anyhow:

/* Just the flags we need, copied from mm.h: */
#define FOLL_WRITE	0x01	/* check pte is writable */
#define FOLL_TOUCH	0x02	/* mark page accessed */

Aside from that this seems OK

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

Jason