From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CC0ECA0EDC for ; Thu, 14 Aug 2025 08:40:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A1E5D900114; Thu, 14 Aug 2025 04:40:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9F590900088; Thu, 14 Aug 2025 04:40:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 90BF7900114; Thu, 14 Aug 2025 04:40:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7CD45900088 for ; Thu, 14 Aug 2025 04:40:24 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 084F1160574 for ; Thu, 14 Aug 2025 08:40:24 +0000 (UTC) X-FDA: 83774716368.12.39E4606 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf05.hostedemail.com (Postfix) with ESMTP id 674F810000D for ; Thu, 14 Aug 2025 08:40:22 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZZ5tqXiS; spf=pass (imf05.hostedemail.com: domain of rppt@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1755160822; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ALAQ1hCCvfMNneTPSDmW2WXC/XQXQuv7liTcDor4eJI=; b=Xejzy4iP/x6ePQVQv9N3N9MqsVrOSEPCt3j40WLES2sUDg5wIambQrKja5X6VfX2bAVUXa 6PkdG7lIC0tYP0kThKT2B8qPa+8CcvitAHUDmfdr5HiO4thLNHmt672UmGyo42LRcn9rDH KBdNVAarx8efCr4W/lmm9qhuS7BUhxo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1755160822; a=rsa-sha256; cv=none; b=bHNZd7hZ5EyfrL2NnYjps8Gvumhp1Bjx/FTYLZyE5k8jVSFJpDxn2pIfmRHVXINRfSXrPX trBVsmNH/LwInIHInNrVTMg8t5sUJfFLshtf+22M6CvrAY9VQnGXhN4lxDgpOdRLVDOLO/ RE3ussPF/1Y6vlavfEK8SZMttW9F9qY= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ZZ5tqXiS; spf=pass (imf05.hostedemail.com: domain of rppt@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id AB33DA5576B; Thu, 14 Aug 2025 08:40:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FC94C4AF09; Thu, 14 Aug 2025 08:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755160821; bh=zqmt4Jj8Tl4AG5pUIufRcdzVJq4JYdl8O/zAhI2YC70=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZZ5tqXiSOEwYFaq79WS5EhkFn8Z5imGYNmIePfhjJTAhyZJEgDA7Bwly8nCqYBrRu d5UBO0ASyeI4lggmFmZP5Ii3320gaokMa2FN+oxetsh12TTGQ+8oWdtIFgLAmFwDa8 JmyiIhU5NvRChb93aRk4sfsoi6H8QvZGvsj0WePGnaiA2KQ0/+8V6zFvTPRMYPKrqn 1S4BU4qOOBW810STnQ9C/RqF+W8yGtXS38JRPzp9ypmj54uCmkS4f0kA57Jmi573iT nQhBwXuhJUpx99j/CnWWG20Qpb4JWWkPn9hA8ESGXnWKA625fvfdzX3MjXix2LjKhh b4YJ1g7zPit1g== Date: Thu, 14 Aug 2025 11:39:57 +0300 From: Mike Rapoport To: Lorenzo Stoakes Cc: Andrew Morton , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , "David S . Miller" , Andreas Larsson , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Xu Xin , Chengming Zhou , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , David Rientjes , Shakeel Butt , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , Masami Hiramatsu , Oleg Nesterov , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Jason Gunthorpe , John Hubbard , Peter Xu , Jann Horn , Pedro Falcato , Matthew Wilcox , Mateusz Guzik , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH 08/10] mm: update fork mm->flags initialisation to use bitmap Message-ID: References: <9fb8954a7a0f0184f012a8e66f8565bcbab014ba.1755012943.git.lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9fb8954a7a0f0184f012a8e66f8565bcbab014ba.1755012943.git.lorenzo.stoakes@oracle.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 674F810000D X-Stat-Signature: unu9t9c3hpynqps4bodudk9kr69y6kaw X-HE-Tag: 1755160822-347243 X-HE-Meta: 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 HNctoFCu zoaVkTmdUc5Ia5J3Yibu7fu3a3bb02NbR69AXdqAEzJJcWNKkkPdHn7ZuhA1OvrPvIwnzKCX9Nr0/bUFeIy5vTQ54724VfWDQErGM3dzRQMhgwkBP2z4KW7RMDEkH4hEcb2t1pK4CZxCvl29Q3J0ke0tXQbfzYVdWe4Rnzv/C2DxnqRjmc200ZnMXSI6JamdpAOCKic6RaHKz2hqLV5HADq6ilEUg2TcYw3rQI2tKztjCP+DaKcOSgBJPTHjWduLBpJogAmE/2f1DxJ66Lcu9yjQjxn0mVfsvLtlUIJ+slAuuXs4xCVamaiQeqj3LVR9ZCZiHV/E8KhS+RSU= 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, Aug 12, 2025 at 04:44:17PM +0100, Lorenzo Stoakes wrote: > We now need to account for flag initialisation on fork. We retain the > existing logic as much as we can, but dub the existing flag mask legacy. > > These flags are therefore required to fit in the first 32-bits of the flags > field. > > However, further flag propagation upon fork can be implemented in mm_init() > on a per-flag basis. > > We ensure we clear the entire bitmap prior to setting it, and use > __mm_flags_get_word() and __mm_flags_set_word() to manipulate these legacy > fields efficiently. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) > --- > include/linux/mm_types.h | 13 ++++++++++--- > kernel/fork.c | 7 +++++-- > 2 files changed, 15 insertions(+), 5 deletions(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 38b3fa927997..25577ab39094 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -1820,16 +1820,23 @@ enum { > #define MMF_TOPDOWN 31 /* mm searches top down by default */ > #define MMF_TOPDOWN_MASK _BITUL(MMF_TOPDOWN) > > -#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ > +#define MMF_INIT_LEGACY_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ > MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK |\ > MMF_VM_MERGE_ANY_MASK | MMF_TOPDOWN_MASK) > > -static inline unsigned long mmf_init_flags(unsigned long flags) > +/* Legacy flags must fit within 32 bits. */ > +static_assert((u64)MMF_INIT_LEGACY_MASK <= (u64)UINT_MAX); > + > +/* > + * Initialise legacy flags according to masks, propagating selected flags on > + * fork. Further flag manipulation can be performed by the caller. > + */ > +static inline unsigned long mmf_init_legacy_flags(unsigned long flags) > { > if (flags & (1UL << MMF_HAS_MDWE_NO_INHERIT)) > flags &= ~((1UL << MMF_HAS_MDWE) | > (1UL << MMF_HAS_MDWE_NO_INHERIT)); > - return flags & MMF_INIT_MASK; > + return flags & MMF_INIT_LEGACY_MASK; > } > > #endif /* _LINUX_MM_TYPES_H */ > diff --git a/kernel/fork.c b/kernel/fork.c > index c4ada32598bd..b311caec6419 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1056,11 +1056,14 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, > mm_init_uprobes_state(mm); > hugetlb_count_init(mm); > > + mm_flags_clear_all(mm); > if (current->mm) { > - mm->flags = mmf_init_flags(current->mm->flags); > + unsigned long flags = __mm_flags_get_word(current->mm); > + > + __mm_flags_set_word(mm, mmf_init_legacy_flags(flags)); > mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK; > } else { > - mm->flags = default_dump_filter; > + __mm_flags_set_word(mm, default_dump_filter); > mm->def_flags = 0; > } > > -- > 2.50.1 > -- Sincerely yours, Mike.