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b=a6gwKuW9oAhpz28awT7tOzD1n+MdimdEW3hnK6HX/Pwk1+XgTg4Xlyt9eLHil2iBD 4c4GMOc9uCmKBJoVBbGAhl8tT3jNjpIReAZlqCW9mG/769Wu+AEYJITs9WCHQIjOtT NZzoEU1DRVtvYrtNNr+5zYPqiJjBUDq3U6BIn7d4Rav3nAQPORh8Qn/UtRPV41GL3k a/2CeQUuh2MwDRLdcwiwcSubSLxBy8kYjD764Me4P3zvEp9Jw1BD0jbGAczXb/Kb8D Lyo/1fw1T+p1rkXOpELP2sfKsH3uV35OFK8QmMgV1YVLCsCwDzb+xFE9iOIjgi0wUu sVa+dmWkkF/wQ== Date: Tue, 19 Mar 2024 17:01:38 +0200 From: Mike Rapoport To: "Leizhen (ThunderTown)" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhen Lei Subject: Re: [PATCH 1/1] mm/mm_init.c: eliminate a local variable in mem_debugging_and_hardening_init() Message-ID: References: <20240318135715.312-1-thunder.leizhen@huaweicloud.com> <5fd9144b-fb1c-08fc-8124-1972f86253a4@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5fd9144b-fb1c-08fc-8124-1972f86253a4@huaweicloud.com> X-Rspamd-Queue-Id: 46A0820070 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xqidk1xpwn8q15pu6pgincj66b7a4wrg X-HE-Tag: 1710860563-196233 X-HE-Meta: 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 hLvW1Gtw NQWgB8ydySidChB6drQNUnUfWHuD3WhaVqBlEjFbJXUTJmiK2KnrbQyUMXd2F8rUeL9sZEt8FGubVbTxCPE+rc9MrrO4pJz6wSSkP/LsdLq/E4nW6YYFDmPvA07Sz4/3D2JPCnhzGY7PpaFfKDlP8jyJ5SW7n+ye/30ciLu12h2ErJdr0sMHxfe5JghnWyfDhbryyig0EbzakoxXU3WSFBHfbNngf+0Yab5NipVzBABm/RGfXoJPZbH+HS33xCJsvLciFvg7QRgPMicZAMA6tE+8ha+FpB5PwPzW+xtquBHageXA8Z7HyrTgpwO6PCvouM5YZ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 19, 2024 at 09:22:03AM +0800, Leizhen (ThunderTown) wrote: > > > On 2024/3/19 0:33, Mike Rapoport wrote: > > On Mon, Mar 18, 2024 at 09:57:14PM +0800, thunder.leizhen@huaweicloud.com wrote: > >> From: Zhen Lei > >> > >> The local variable 'page_poisoning_requested' is assigned true at only > >> one point. It can be eliminated by moving the code that depends on it > >> to the location where it is assigned true. This also make the moved > >> code to be compiled only if CONFIG_PAGE_POISONING is set. > > > > I don't see it as much of an improvement and code readability becomes worse > > IMO. > > Yes, the moved branch will be optimized by the compiler if CONFIG_PAGE_POISONING is > not set. But for a reader, he can simply skip over that moved branch when > CONFIG_PAGE_POISONING is not set. Saving one branch at init does not justify the churn and reduced readability. > >> Signed-off-by: Zhen Lei > >> --- > >> mm/mm_init.c | 17 +++++++---------- > >> 1 file changed, 7 insertions(+), 10 deletions(-) > >> > >> diff --git a/mm/mm_init.c b/mm/mm_init.c > >> index 549e76af8f82a8e..3eb217130bcb2b5 100644 > >> --- a/mm/mm_init.c > >> +++ b/mm/mm_init.c > >> @@ -2614,7 +2614,6 @@ DEFINE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled); > >> */ > >> static void __init mem_debugging_and_hardening_init(void) > >> { > >> - bool page_poisoning_requested = false; > >> bool want_check_pages = false; > >> > >> #ifdef CONFIG_PAGE_POISONING > >> @@ -2626,18 +2625,16 @@ static void __init mem_debugging_and_hardening_init(void) > >> (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && > >> debug_pagealloc_enabled())) { > >> static_branch_enable(&_page_poisoning_enabled); > >> - page_poisoning_requested = true; > >> want_check_pages = true; > >> - } > >> -#endif > >> > >> - if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) && > >> - page_poisoning_requested) { > >> - pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " > >> - "will take precedence over init_on_alloc and init_on_free\n"); > >> - _init_on_alloc_enabled_early = false; > >> - _init_on_free_enabled_early = false; > >> + if (_init_on_alloc_enabled_early || _init_on_free_enabled_early) { > >> + pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, " > >> + "will take precedence over init_on_alloc and init_on_free\n"); > >> + _init_on_alloc_enabled_early = false; > >> + _init_on_free_enabled_early = false; > >> + } > >> } > >> +#endif > >> > >> if (_init_on_alloc_enabled_early) { > >> want_check_pages = true; > >> -- > >> 2.34.1 > >> > > > > -- > Regards, > Zhen Lei > -- Sincerely yours, Mike.