linux-kernel - Re: [PATCH] uprobes: replace deprecated kmap_atomic() with kmap_local

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Message-ID: <aYSNKqr2rmO7dHBm@redhat.com>
Date: Thu, 5 Feb 2026 13:29:30 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Carlos López <clopez@...e.de>,
	linux-trace-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	"open list:UPROBES" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] uprobes: replace deprecated kmap_atomic() with
 kmap_local_page()

On 02/05, Peter Zijlstra wrote:
>
> On Thu, Feb 05, 2026 at 11:57:25AM +0100, Carlos López wrote:
> > kmap_atomic() has been deprecated for a few years, and kmap_local_page()
> > should be used instead, so replace it. Since the uprobes code relied on
> > kmap_atomic() disabling page faults to access user pages, add the
> > required calls to keep the existing behavior.
>
> Are those pagefault_disable()s really needed here, or is this just
> cargo-culting?

No, I think there are not needed.

And the (already in tip) patches from Keke do not add pagefault_disable().

is_trap_at_addr() does pagefault_disable() because it is called with
mm->mmap_lock held.

Oleg.