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Thu, 21 May 2026 10:21:38 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: A0sL-wCRL1_7 Date: Thu, 21 May 2026 16:20:31 +0200 From: "Arnd Bergmann" To: "David Laight" , "Arnd Bergmann" Cc: "OGAWA Hirofumi" , "Christian Brauner" , "Jan Kara" , avivdaum , "Adi Nata" , "Andrew Morton" , linux-kernel@vger.kernel.org Message-Id: <8bc8badb-7be9-4445-be5e-1fe80cf628b1@app.fastmail.com> In-Reply-To: <20260521133605.56d09a61@pumpkin> References: <20260515204456.2692208-1-arnd@kernel.org> <20260521133605.56d09a61@pumpkin> Subject: Re: [PATCH] fat: avoid stack overflow warning Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, May 21, 2026, at 14:36, David Laight wrote: > On Fri, 15 May 2026 22:44:46 +0200 > Arnd Bergmann wrote: > >> From: Arnd Bergmann >> >> Building the fat kunit tests on with -fsanitize=alignment >> reveals some rather excessive stack usage: > > What on earth is -fsanitize=alignment doing here? > (Or even what do it do in general!) The idea is that the compiler adds sanity checks on accesses to variables that may be misaligned and print a runtime warning if this actually happens, see lib/ubsan.c. As I understand it, the increased stack usage is an unintended side-effect here, which is the result of skipping some of the default optimization steps or being less aggressive about function inlining. Arnd