linux-kernel - Re: [PATCH] [suggestion] mm/gup: avoid IS_ERR_OR

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Message-ID: <ZHHSwRzksE+KukTK@nvidia.com>
Date:   Sat, 27 May 2023 06:52:01 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lorenzo Stoakes <lstoakes@...il.com>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] [suggestion] mm/gup: avoid IS_ERR_OR_NULL

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