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 E6D12C02183 for ; Wed, 15 Jan 2025 11:04:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 85BE66B0098; Wed, 15 Jan 2025 06:04:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 80C5C6B0099; Wed, 15 Jan 2025 06:04:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D5296B009A; Wed, 15 Jan 2025 06:04:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 49FEA6B0098 for ; Wed, 15 Jan 2025 06:04:13 -0500 (EST) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id BF022C1251 for ; Wed, 15 Jan 2025 11:04:12 +0000 (UTC) X-FDA: 83009401944.28.1E9E4A1 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf07.hostedemail.com (Postfix) with ESMTP id 27FFE4000B for ; Wed, 15 Jan 2025 11:04:10 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=VC2bhh+G; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of a.hindborg@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736939051; a=rsa-sha256; cv=none; b=j7wxOIUMdgp6XwRUPLZxR6CT+7WRwIXTcoDEQR3UJirglr26gUHL5CUPmxRP9jYKwCGJP/ LE+ZWs7FiB6OYQfC7yh0oPNoNfoafEiZzpewDL91YkUNZGTwDtFj09TwDwmabzbWDj7hle QsUXkiPOowI8dIxEnYYlV6PB/Mk1c9U= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=VC2bhh+G; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of a.hindborg@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736939051; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=sqZ9GOQUMDvx1TWc/Fb5Zz/FGQQ18lE/mvBJ4eqVBZI=; b=nvcOadcR8l0RLa4du5ITK9eQ5dotCQLUCb3PiRMBBqDOAGrBC+vVm08fNoNxK2yTzUtTZM GVg+PLqF9l0GrIe381tba9BQ9qjWSwqB21tin+r0HPvO0/6SB7Vqr3a8mCTK3JoMsR4KAN EOSaJK6XjZfnOeXqyYQtVkx+092jg7Q= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 51BF3A41D49; Wed, 15 Jan 2025 11:02:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D9F6C4CEE2; Wed, 15 Jan 2025 11:04:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736939050; bh=hkRFo3uTdbREugXqIkyYEWEUEBU0dTtp3fPfcRlTA9M=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=VC2bhh+GY4NLpy+BWOvTA2yBwzQp6icpa5jKq0+VtFxmhergYso4CkZFYdP6A1I1D brraymeP9XIFPCFzGCcuspw9flSaAcCGyXLkVsdaLXJ0C/fW0/bBkW2YP3KG883HtO uwQn2zEWetjmlmbU91iRGZgOk6QX4Me6NFxZ0EMlCBZvdrCUsrsybRZcAJWqcATAw0 nSO1YArgUad8qvqATWgUzcJKCDEcKjKGWbz0cRsUvblYmN54yY+nC3uHwwubijGt6V cUia+kyZIQzPPmBvIgSWKpkL874drTjMnkGOCl2atmZj9THHSr92kSBDlQhQCjdlfX lOvZSbMptSO8w== From: Andreas Hindborg To: "Alice Ryhl" Cc: "Miguel Ojeda" , "Matthew Wilcox" , "Lorenzo Stoakes" , "Vlastimil Babka" , "John Hubbard" , "Liam R. Howlett" , "Andrew Morton" , "Greg Kroah-Hartman" , "Arnd Bergmann" , "Christian Brauner" , "Jann Horn" , "Suren Baghdasaryan" , "Alex Gaynor" , "Boqun Feng" , "Gary Guo" , =?utf-8?Q?Bj=C3=B6rn?= Roy Baron , "Benno Lossin" , "Trevor Gross" , , , Subject: Re: [PATCH v11 4/8] mm: rust: add lock_vma_under_rcu In-Reply-To: (Alice Ryhl's message of "Mon, 13 Jan 2025 11:04:36 +0100") References: <20241211-vma-v11-0-466640428fc3@google.com> <20241211-vma-v11-4-466640428fc3@google.com> <87jzbzbxrk.fsf@kernel.org> User-Agent: mu4e 1.12.7; emacs 29.4 Date: Wed, 15 Jan 2025 10:34:15 +0100 Message-ID: <87wmewe7zc.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: k58bzebt1rupb75j34qmd5ggw7aei5rz X-Rspam-User: X-Rspamd-Queue-Id: 27FFE4000B X-Rspamd-Server: rspam08 X-HE-Tag: 1736939050-759640 X-HE-Meta: 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 B6mMmRv3 ZD0uVXUxPMqheWhuuWhQshY30GU+uK8fuhC1p9OqFRNguLLe74WrdJMKnGBfmacM0iqX0EZDol/pMPKlXhLb/1rS29McowKDBl/U6hdL64NH+orVejM9CwuoSuE5C4NBw7udPJoITHHmu76dwRDnTpy0lvX5eo7DRyIFS95nVenuej6Q++PVDCJakUQzt272GlDdHqnZhcCazrP8FnaczpHfZwtnx/wR6pNYfLhHSSkoN2y0LVNFV+DTavjqPEPtkocHJDK8YLy730HoXqJDOKOfOxPZxytkoEFuzJvMPPR3+k79fpz/OC66YZGOx7vGZzpSSgJG404UoItTCV/dJpQU2zOHbCUyqTVNDz/TYy0oQXrxN93eVT67kskeX3LwnqY4hS1nxO2x/Cv5qs87w8g3yxxR5HjnQnPEL X-Bogosity: Ham, tests=bogofilter, spamicity=0.134538, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: "Alice Ryhl" writes: > On Mon, Dec 16, 2024 at 3:50=E2=80=AFPM Andreas Hindborg wrote: >> >> "Alice Ryhl" writes: >> >> > Currently, the binder driver always uses the mmap lock to make changes >> > to its vma. Because the mmap lock is global to the process, this can >> > involve significant contention. However, the kernel has a feature call= ed >> > per-vma locks, which can significantly reduce contention. For example, >> > you can take a vma lock in parallel with an mmap write lock. This is >> > important because contention on the mmap lock has been a long-term >> > recurring challenge for the Binder driver. >> > >> > This patch introduces support for using `lock_vma_under_rcu` from Rust. >> > The Rust Binder driver will be able to use this to reduce contention on >> > the mmap lock. >> > >> > Acked-by: Lorenzo Stoakes (for mm bits) >> > Reviewed-by: Jann Horn >> > Signed-off-by: Alice Ryhl >> > --- >> > rust/helpers/mm.c | 5 +++++ >> > rust/kernel/mm.rs | 56 ++++++++++++++++++++++++++++++++++++++++++++++= +++++++++ >> > 2 files changed, 61 insertions(+) >> > >> > diff --git a/rust/helpers/mm.c b/rust/helpers/mm.c >> > index 7b72eb065a3e..81b510c96fd2 100644 >> > --- a/rust/helpers/mm.c >> > +++ b/rust/helpers/mm.c >> > @@ -43,3 +43,8 @@ struct vm_area_struct *rust_helper_vma_lookup(struct= mm_struct *mm, >> > { >> > return vma_lookup(mm, addr); >> > } >> > + >> > +void rust_helper_vma_end_read(struct vm_area_struct *vma) >> > +{ >> > + vma_end_read(vma); >> > +} >> > diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs >> > index ace8e7d57afe..425b73a9dfe6 100644 >> > --- a/rust/kernel/mm.rs >> > +++ b/rust/kernel/mm.rs >> > @@ -13,6 +13,7 @@ >> > use core::{ops::Deref, ptr::NonNull}; >> > >> > pub mod virt; >> > +use virt::VmAreaRef; >> > >> > /// A wrapper for the kernel's `struct mm_struct`. >> > /// >> > @@ -170,6 +171,32 @@ pub unsafe fn from_raw<'a>(ptr: *const bindings::= mm_struct) -> &'a MmWithUser { >> > unsafe { &*ptr.cast() } >> > } >> > >> > + /// Attempt to access a vma using the vma read lock. >> > + /// >> > + /// This is an optimistic trylock operation, so it may fail if th= ere is contention. In that >> > + /// case, you should fall back to taking the mmap read lock. >> > + /// >> > + /// When per-vma locks are disabled, this always returns `None`. >> > + #[inline] >> > + pub fn lock_vma_under_rcu(&self, vma_addr: usize) -> Option> { >> > + #[cfg(CONFIG_PER_VMA_LOCK)] >> > + { >> > + // SAFETY: Calling `bindings::lock_vma_under_rcu` is alwa= ys okay given an mm where >> > + // `mm_users` is non-zero. >> > + let vma =3D unsafe { bindings::lock_vma_under_rcu(self.as= _raw(), vma_addr as _) }; >> >> Is `as _` the right approach here? > > We can drop it once the FFI integer types are fixed. It's late in the > cycle, so this patch probably won't make it for 6.14. This means I can > remove the casts entirely before this is merged. Otherwise we can > remove them in a follow-up. Sounds good to me =F0=9F=91=8D Best regards, Andreas Hindborg