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Date:   Sat, 27 May 2023 06:52:01 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Lorenzo Stoakes <lstoakes@gmail.com>
Cc:     Arnd Bergmann <arnd@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        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>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-perf-users@vger.kernel.org
Subject: Re: [PATCH] [suggestion] mm/gup: avoid IS_ERR_OR_NULL
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On Sat, May 20, 2023 at 10:12:40AM +0100, Lorenzo Stoakes wrote:
> > No, this returning 0 on failure is a foot gun. Failing to pin a single
> > page is always an error, the only question is what sub reason caused
> > the error to happen. There is no third case where it is not an error.
> 
> The uprobe path thinks otherwise, but maybe the answer is that we just need
> to -EFAULT on missing VMA and -EPERM on invalid flags.

I think uprobe is just broken to think there is a third outcome. Let's
just fix it instead of trying to pretend it makes sense.

Jason