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Mon, 05 Jul 2021 04:44:50 -0700 (PDT) Date: Mon, 5 Jul 2021 13:44:44 +0200 From: Marco Elver To: Mel Gorman Cc: akpm@linux-foundation.org, glider@google.com, dvyukov@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Andrii Nakryiko , Daniel Borkmann , Vlastimil Babka , Yang Shi , bpf@vger.kernel.org, Alexei Starovoitov Subject: Re: [PATCH] Revert "mm/page_alloc: make should_fail_alloc_page() static" Message-ID: References: <20210705103806.2339467-1-elver@google.com> <20210705113723.GN3840@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210705113723.GN3840@techsingularity.net> User-Agent: Mutt/2.0.5 (2021-01-21) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 05, 2021 at 12:37PM +0100, Mel Gorman wrote: > On Mon, Jul 05, 2021 at 12:38:06PM +0200, Marco Elver wrote: > > This reverts commit f7173090033c70886d925995e9dfdfb76dbb2441. > > > > Commit 76cd61739fd1 ("mm/error_inject: Fix allow_error_inject function > > signatures") explicitly made should_fail_alloc_page() non-static, due to > > worries of remaining compiler optimizations in the absence of function > > side-effects while being noinline. > > > > Furthermore, kernel/bpf/verifier.c pushes should_fail_alloc_page onto > > the btf_non_sleepable_error_inject BTF IDs set, which when enabling > > CONFIG_DEBUG_INFO_BTF results in an error at the BTFIDS stage: > > > > FAILED unresolved symbol should_fail_alloc_page > > > > To avoid the W=1 warning, add a function declaration right above the > > function itself, with a comment it is required in a BTF IDs set. > > > > Fixes: f7173090033c ("mm/page_alloc: make should_fail_alloc_page() static") > > Cc: Mel Gorman > > Cc: Alexei Starovoitov > > Signed-off-by: Marco Elver > > Acked-by: Mel Gorman > > Out of curiousity though, why does block/blk-core.c not require > something similar for should_fail_bio? It seems kernel/bpf/verifier.c doesn't refer to it in an BTF IDs set. Looks like should_fail_alloc_page is special for BPF purposes. I'm not a BPF maintainer, so hopefully someone can explain why should_fail_alloc_page is special for BPF. Thanks, -- Marco