From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F49D3CBE84; Tue, 2 Jun 2026 09:10:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780391412; cv=none; b=th7h7vmfK+WvbLvmCRMj9Gmc6YBGLdOPYiNb5jHUYFm4syFj7SoJzSn9tCgJpYKeBfAe8pqQwAZ5gDSGBHREyrKvfcMpiMkTjBq9qeq/egyCTMsGCCkGp28JxwtQLDmPsJd4DVS7trUVXcThVN/1EOGgleoULoNxVU3EDqj9gp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780391412; c=relaxed/simple; bh=v8ADpKuVUuJdvfsdxL+3no0PVB96FFml4gf9uFICkMM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S2Hulev79uSzyYFEzWagPRQoMVb4qfsuxyqjo9QQ/tOvucjbo44vvo9dpkcisiCKS5UH1XasmTkZdraCmmMbFNo1mjem5mu8Z2M2qTK2Be3mi5icEju3907vJMpULE10cE1yIIfB84yFqt9gKuEKOMN7wHn/I/K+Cc3Z7rhMQF0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JoneNJ5b; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JoneNJ5b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 688A21F00899; Tue, 2 Jun 2026 09:10:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780391411; bh=kq5G0oHDkBWFEFFqoWIBja9YbwYgAYGaHMrsEu/NhUE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=JoneNJ5b/Q0IaGwhfeEspKw8KT/XrtpSuyDwYnlA1H7DFKwtqJnKWbwiRyhY/u3XK DeQSI09SyNWmgWRnO6BhSHJr49DCNaeiDjDBqO9isA/PYFXcAJydRbYe8C3dp6VecI lGGreseU3n2X9YSMa5sZvg5nOzKPeu4lFHilZs8VtxwenM3VDQ4dbp6bSK6Np9nUAF uukUzKeptcEDqZf8vJ5Izy3O1wagGDcsutLa5/1s5vebHAZkHnaTuFxQID+JzFqd1O Yo3hSlTEMi8bx97RafJX7n6Nz0XLx2Zlb0vpPDUkGTNRV7Gzed0IQlV9hKvmjtBUio m2PV4G0DuQgfw== Message-ID: <3674d3a8-b30e-4bf1-a4ab-0f82c494d131@kernel.org> Date: Tue, 2 Jun 2026 11:10:07 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH][v2] mm/mempool: Untangle CONFIG_SLUB_DEBUG_ON abuse and switch to static key Content-Language: en-US To: lirongqing , Jonathan Corbet , Shuah Khan , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Matthew Wilcox , Usama Arif References: <20260602062142.1790-1-lirongqing@baidu.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260602062142.1790-1-lirongqing@baidu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/2/26 08:21, lirongqing wrote: > From: Li RongQing > > The mempool subsystem historically wrapped its debugging logic inside an > merely defines compile-time defaults for SLUB and caused two flaws: > > 1. On production kernels where CONFIG_SLUB_DEBUG=y but > CONFIG_SLUB_DEBUG_ON=n, mempool debugging was completely compiled out > at compile time. > 2. On kernels with CONFIG_SLUB_DEBUG_ON=y, mempool debugging stayed active > even if a user explicitly disabled slub debugging at boot time. > > Clean up this mess by removing the #ifdef and switching to a runtime static > key (mempool_debug_enabled), allowing mempool debugging to be toggled > cleanly via its own boot parameter. > > Suggested-by: Vlastimil Babka (SUSE) > Signed-off-by: Li RongQing > Cc: Vlastimil Babka > Cc: Harry Yoo > Cc: Andrew Morton > Cc: Hao Li > Cc: Christoph Lameter > Cc: David Rientjes > Cc: Roman Gushchin > Cc: Matthew Wilcox > Cc: Usama Arif > --- > Diff with v1: > Rewrite commit message, change early_param to __setup > > Documentation/admin-guide/kernel-parameters.txt | 5 ++++ > mm/mempool.c | 32 ++++++++++++++++++------- > 2 files changed, 28 insertions(+), 9 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 642659b..89b5994 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -3980,6 +3980,11 @@ Kernel parameters > Note that even when enabled, there are a few cases where > the feature is not effective. > > + mempool_debug [MM] > + Enable mempool debugging. This enables element > + poison checking when freeing elements back to the > + pool. Useful for debugging mempool corruption. > + > memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest > Format: > default : 0 > diff --git a/mm/mempool.c b/mm/mempool.c > index db23e0e..71e4b54 100644 > --- a/mm/mempool.c > +++ b/mm/mempool.c > @@ -16,11 +16,28 @@ > #include > #include > #include > +#include > +#include > #include "slab.h" > > static DECLARE_FAULT_ATTR(fail_mempool_alloc); > static DECLARE_FAULT_ATTR(fail_mempool_alloc_bulk); > > +/* > + * Debugging support for mempool using static key. > + * > + * This allows enabling mempool debug at boot time via: > + * mempool_debug > + */ > +static DEFINE_STATIC_KEY_FALSE(mempool_debug_enabled); > + > +static int __init mempool_debug_setup(char *str) > +{ > + static_branch_enable(&mempool_debug_enabled); > + return 1; > +} > +__setup("mempool_debug", mempool_debug_setup); > + > static int __init mempool_faul_inject_init(void) > { > int error; > @@ -37,7 +54,6 @@ static int __init mempool_faul_inject_init(void) > } > late_initcall(mempool_faul_inject_init); > > -#ifdef CONFIG_SLUB_DEBUG_ON > static void poison_error(struct mempool *pool, void *element, size_t size, > size_t byte) > { > @@ -73,6 +89,9 @@ static void __check_element(struct mempool *pool, void *element, size_t size) > > static void check_element(struct mempool *pool, void *element) > { > + if (!static_branch_unlikely(&mempool_debug_enabled)) > + return; With static keys it's better to have the check in the caller of check_element so we skip over that call if it's disabled, and not do a call that immediately returns. Since there's a single caller, there's no need for an extra inline wrapper. > + > /* Skip checking: KASAN might save its metadata in the element. */ > if (kasan_enabled()) > return; > @@ -112,6 +131,9 @@ static void __poison_element(void *element, size_t size) > > static void poison_element(struct mempool *pool, void *element) > { > + if (!static_branch_unlikely(&mempool_debug_enabled)) > + return; Ditto. > + > /* Skip poisoning: KASAN might save its metadata in the element. */ > if (kasan_enabled()) > return; > @@ -140,14 +162,6 @@ static void poison_element(struct mempool *pool, void *element) > #endif > } > } > -#else /* CONFIG_SLUB_DEBUG_ON */ > -static inline void check_element(struct mempool *pool, void *element) > -{ > -} > -static inline void poison_element(struct mempool *pool, void *element) > -{ > -} > -#endif /* CONFIG_SLUB_DEBUG_ON */ > > static __always_inline bool kasan_poison_element(struct mempool *pool, > void *element)