From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 07775C2FB for ; Mon, 12 May 2025 00:51:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747011097; cv=none; b=RGQdFEsohyY3F+i+VdPBZdgba/hDYYgq/N15ujyqxBRkfiGMxukrXxbdQvYynOvD1SXLqMLfVhFWkgbUZwcTn/mjtsJSaAZkKaKVhbaxJNiwb/9irn2KqkV8Rg9jKVadv9A0chYnNjqPN2OEDr+UdpXwt2vTQIqnRMh6iTj1uIY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747011097; c=relaxed/simple; bh=0HuIxe7i3Q96BIDE3hG967fOwn0Tul8uCcE0BOhorYs=; h=Date:To:From:Subject:Message-Id; b=DXXhmXrRHp05juhJkQ0NLX6zy9nmhFpNp5nQwpNlAxbfSsLWG8TxSM/BybuFeH5SoB6sNHgL9Vzd3i7V5/lEnIRU5d1chQDzEhCXYWNYuwdkVtJ/5sdVHlxFno99IKbjgMTvaSK8U7FFxfDYn6MseP/Y5OAi0r8HehEseqTYih4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Ry6iQ3Zu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Ry6iQ3Zu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF267C4CEE4; Mon, 12 May 2025 00:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1747011096; bh=0HuIxe7i3Q96BIDE3hG967fOwn0Tul8uCcE0BOhorYs=; h=Date:To:From:Subject:From; b=Ry6iQ3ZuvtsUu31OThySXyErAYRTBOOstfUX8LSPEbQUeDxhz7r5MOJISMZI9r3jR Jhj//JxSYGClcub5AEtrMKQCcGDynGGsGUS1e4rTEXYWqGtUN9jwMADDJyRedYJd3y 0NUIrZgFpPQGGMfHYHtuZ55UxH3vxEPRrQP01H0U= Date: Sun, 11 May 2025 17:51:36 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,vbabka@suse.cz,tmgross@umich.edu,surenb@google.com,ojeda@kernel.org,lorenzo.stoakes@oracle.com,Liam.Howlett@Oracle.com,jhubbard@nvidia.com,jannh@google.com,gregkh@linuxfoundation.org,gary@garyguo.net,boqun.feng@gmail.com,bjorn3_gh@protonmail.com,benno.lossin@proton.me,balbirs@nvidia.com,arnd@arndb.de,alex.gaynor@gmail.com,a.hindborg@kernel.org,aliceryhl@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-rust-add-mmput_async-support.patch removed from -mm tree Message-Id: <20250512005136.CF267C4CEE4@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: rust: add mmput_async support has been removed from the -mm tree. Its filename was mm-rust-add-mmput_async-support.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Alice Ryhl Subject: mm: rust: add mmput_async support Date: Tue, 08 Apr 2025 09:22:42 +0000 Adds an MmWithUserAsync type that uses mmput_async when dropped but is otherwise identical to MmWithUser. This has to be done using a separate type because the thing we are changing is the destructor. Rust Binder needs this to avoid a certain deadlock. See commit 9a9ab0d96362 ("binder: fix race between mmput() and do_exit()") for details. It's also needed in the shrinker to avoid cleaning up the mm in the shrinker's context. Link: https://lkml.kernel.org/r/20250408-vma-v16-5-d8b446e885d9@google.com Signed-off-by: Alice Ryhl Acked-by: Lorenzo Stoakes Acked-by: Liam R. Howlett Reviewed-by: Andreas Hindborg Reviewed-by: Gary Guo Cc: Alex Gaynor Cc: Arnd Bergmann Cc: Balbir Singh Cc: Benno Lossin Cc: Björn Roy Baron Cc: Boqun Feng Cc: Greg Kroah-Hartman Cc: Jann Horn Cc: John Hubbard Cc: Matthew Wilcox (Oracle) Cc: Miguel Ojeda Cc: Suren Baghdasaryan Cc: Trevor Gross Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- rust/kernel/mm.rs | 51 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) --- a/rust/kernel/mm.rs~mm-rust-add-mmput_async-support +++ a/rust/kernel/mm.rs @@ -111,6 +111,50 @@ impl Deref for MmWithUser { } } +/// A wrapper for the kernel's `struct mm_struct`. +/// +/// This type is identical to `MmWithUser` except that it uses `mmput_async` when dropping a +/// refcount. This means that the destructor of `ARef` is safe to call in atomic +/// context. +/// +/// # Invariants +/// +/// Values of this type are always refcounted using `mmget`. The value of `mm_users` is non-zero. +#[repr(transparent)] +pub struct MmWithUserAsync { + mm: MmWithUser, +} + +// SAFETY: It is safe to call `mmput_async` on another thread than where `mmget` was called. +unsafe impl Send for MmWithUserAsync {} +// SAFETY: All methods on `MmWithUserAsync` can be called in parallel from several threads. +unsafe impl Sync for MmWithUserAsync {} + +// SAFETY: By the type invariants, this type is always refcounted. +unsafe impl AlwaysRefCounted for MmWithUserAsync { + #[inline] + fn inc_ref(&self) { + // SAFETY: The pointer is valid since self is a reference. + unsafe { bindings::mmget(self.as_raw()) }; + } + + #[inline] + unsafe fn dec_ref(obj: NonNull) { + // SAFETY: The caller is giving up their refcount. + unsafe { bindings::mmput_async(obj.cast().as_ptr()) }; + } +} + +// Make all `MmWithUser` methods available on `MmWithUserAsync`. +impl Deref for MmWithUserAsync { + type Target = MmWithUser; + + #[inline] + fn deref(&self) -> &MmWithUser { + &self.mm + } +} + // These methods are safe to call even if `mm_users` is zero. impl Mm { /// Returns a raw pointer to the inner `mm_struct`. @@ -162,6 +206,13 @@ impl MmWithUser { unsafe { &*ptr.cast() } } + /// Use `mmput_async` when dropping this refcount. + #[inline] + pub fn into_mmput_async(me: ARef) -> ARef { + // SAFETY: The layouts and invariants are compatible. + unsafe { ARef::from_raw(ARef::into_raw(me).cast()) } + } + /// Attempt to access a vma using the vma read lock. /// /// This is an optimistic trylock operation, so it may fail if there is contention. In that _ Patches currently in -mm which might be from aliceryhl@google.com are