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Wysocki" , David Airlie , Simona Vetter , Alexander Viro , Christian Brauner , Jan Kara , Daniel Almeida , Viresh Kumar , Nishanth Menon , Stephen Boyd , Bjorn Helgaas , =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= , Boqun Feng , Uladzislau Rezki , Lorenzo Stoakes , Vlastimil Babka , "Liam R. Howlett" , Igor Korotin , Pavel Tikhomirov , Boqun Feng , Igor Korotin , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-pci@vger.kernel.org, Andreas Hindborg , driver-core@lists.linux.dev, Asahi Lina X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4419; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=Rg2v6tz0XwCXNwaYk5oY+uEcooXMgwXc01B3VEHvrOM=; b=owEBbQKS/ZANAwAKAfpQKQiqxb3QAcsmYgBqIdvqHYkB8MyfIOoBDF1dSU61Fxib1oa4Dt9RG PgIQ0wtLluJAjMEAAEKAB0WIQRXitnI2WZ2JirAaob6UCkIqsW90AUCaiHb6gAKCRD6UCkIqsW9 0IqcD/sFotgaGhMKDajo2vE0qEhGdVZ65uCHkiTMoKJrdcB+u/EW3F8VpV/IBvLFdHjNpsvogco E6hiRlSOOQyWBKf6qLQT3kNcckJUFca2rKOfxiHDoyO0g3ZhjKdB36WHeMksAohI3e5393Ar7A3 JMomk1USO6WVyn0G69K23Cfa5gxuU0ODBR7cKy8U9dnlAnseoKo790PpO1ndbKqIm1XmJflmg9Z BamGGuMTLke1RIf510z6jyUIfdP8QxBXpXDELofQVg1il1vgaiS/tSkjhE5CLPJMkfVAEgul4hZ LyLB4oVXmjIOosFVwOx3BIagjIV19MAkiMIAY6wM0ovnXQCt55Qi6Py+KJy0cAsokL+xT//Xdjn p9iM3+z839r8nvxM97PFts/FKYW1cByF4oDNG+l4W250i9L/Nj9I1xyNMaA7e73/W4sG9ez0aNK snOob3lVbaC6MC/UYTey2mtt+QzOsF4BIfH2cvKEVRwH8aAKqChai103IF19OccUq7xLqyRQYf3 gEGpIVah68briyXNnatyiyC9YSJJr2dVfLa6atP8DrONRO67JJ0tvEyiDWHoO3VvaZ/WV5fXj1c kYW2Iclhgcq7FVDvpyhKjFxoQ2h6IAQD0233nnJeT/ZRmTs6tk4ymr07hr22Hg8IOkv612sntSB qvL9y8ZQV0udSbA== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 32CAB20006 X-Stat-Signature: zmiy4dgsz5an3sck9nrjg4rnm6ucytfe X-Rspam-User: X-HE-Tag: 1780604046-398613 X-HE-Meta: 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 tfEL8+Ol ynHUh8jZTLmPrdjssvmX+Cu7lfwR2Mjq2iuZM+6X0pUuDn1eBckJJUuTROnCvpgQDkz878SwPIMcceDl8nDkY7bQ1W3WFQFvQWSgPJigg6rcqIaC+q19qSDcU3Kmg4ZEiENCtvHSDAkh9QAIK8/0caT7wcNbgG4kqSJfVjEsW+hhyr93AsKYXz2pl74A5EXgP4yrMcP73WNhaeQxkrig6gorsqoSqSV9ee++1OJCl8zArrYt7m/WQX0AUYxPue29kn5sMLS1VFc6hwLt4uan+gAVNpLDavgu1Gg7bqt59CiWFhAFulxByMDjeFkRTHKgiG51GoYziasy3rRJSAq7UyEjH/Jz0M0x5RZzkQYINlv9wYNBVt0oYkvnM2uEOhsGgPktGWEi11TOrfyNHwFV5P4uKbTYRevK5U1wULEDOeNyF7O8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Asahi Lina This allows Page references to be returned as borrowed references, without necessarily owning the struct page. Signed-off-by: Asahi Lina [ Andreas: Fix formatting and add a safety comment. ] Signed-off-by: Andreas Hindborg --- rust/kernel/page.rs | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs index 3bdcee0e16a8..844c75e54134 100644 --- a/rust/kernel/page.rs +++ b/rust/kernel/page.rs @@ -10,6 +10,11 @@ bindings, error::code::*, error::Result, + types::{ + Opaque, + Ownable, + Owned, // + }, uaccess::UserSliceReader, // }; use core::{ @@ -105,7 +110,7 @@ pub const fn page_align(addr: usize) -> Option { /// /// [`VBox`]: kernel::alloc::VBox /// [`Vmalloc`]: kernel::alloc::allocator::Vmalloc -pub struct BorrowedPage<'a>(ManuallyDrop, PhantomData<&'a Page>); +pub struct BorrowedPage<'a>(ManuallyDrop>, PhantomData<&'a Page>); impl<'a> BorrowedPage<'a> { /// Constructs a [`BorrowedPage`] from a raw pointer to a `struct page`. @@ -115,7 +120,9 @@ impl<'a> BorrowedPage<'a> { /// - `ptr` must point to a valid `bindings::page`. /// - `ptr` must remain valid for the entire lifetime `'a`. pub unsafe fn from_raw(ptr: NonNull) -> Self { - let page = Page { page: ptr }; + let page: NonNull = + // SAFETY: By function safety requirements `ptr` is non null. + unsafe { NonNull::new_unchecked(ptr.as_ptr().cast()) }; // INVARIANT: The safety requirements guarantee that `ptr` is valid for the entire lifetime // `'a`. @@ -127,7 +134,8 @@ impl<'a> Deref for BorrowedPage<'a> { type Target = Page; fn deref(&self) -> &Self::Target { - &self.0 + // SAFETY: By type invariant `self.0` is convertible to a reference for `'a`. + unsafe { self.0.as_ref() } } } @@ -148,8 +156,9 @@ pub trait AsPageIter { /// # Invariants /// /// The pointer is valid, and has ownership over the page. +#[repr(transparent)] pub struct Page { - page: NonNull, + page: Opaque, } // SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across @@ -183,19 +192,20 @@ impl Page { /// # Ok::<(), kernel::alloc::AllocError>(()) /// ``` #[inline] - pub fn alloc_page(flags: Flags) -> Result { + pub fn alloc_page(flags: Flags) -> Result, AllocError> { // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it // is always safe to call this method. let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) }; let page = NonNull::new(page).ok_or(AllocError)?; - // INVARIANT: We just successfully allocated a page, so we now have ownership of the newly - // allocated page. We transfer that ownership to the new `Page` object. - Ok(Self { page }) + // SAFETY: We just successfully allocated a page, so we now have ownership of the newly + // allocated page. We transfer that ownership to the new `Owned` object. + // Since `Page` is transparent, we can cast the pointer directly. + Ok(unsafe { Owned::from_raw(page.cast()) }) } /// Returns a raw pointer to the page. pub fn as_ptr(&self) -> *mut bindings::page { - self.page.as_ptr() + Opaque::cast_into(&self.page) } /// Get the node id containing this page. @@ -370,10 +380,12 @@ pub unsafe fn copy_from_user_slice_raw( } } -impl Drop for Page { +impl Ownable for Page { #[inline] - fn drop(&mut self) { - // SAFETY: By the type invariants, we have ownership of the page and can free it. - unsafe { bindings::__free_pages(self.page.as_ptr(), 0) }; + unsafe fn release(&mut self) { + let ptr: *mut Self = self; + // SAFETY: By the function safety requirements, we have ownership of the page and can free + // it. Since Page is transparent, we can cast the raw pointer directly. + unsafe { bindings::__free_pages(ptr.cast(), 0) }; } } -- 2.51.2