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Howlett" , Viresh Kumar , Nishanth Menon , Stephen Boyd , Bjorn Helgaas , =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= , Boqun Feng , Vlastimil Babka , Uladzislau Rezki , Boqun Feng 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 , Asahi Lina , Asahi Lina X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=4409; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=7QArePJ/pjN7cnWoG0Oe4tA+Fg7KV4ZTWL57uMIfL+M=; b=owEBbQKS/ZANAwAKAeG4Gj55KGN3AcsmYgBpnYj6lI/S2fx31p6OdqYp54cwV/ZbM95Hj1Ip+ BqHsBArEFuJAjMEAAEKAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCaZ2I+gAKCRDhuBo+eShj d+jAEADCyxHHAeQ9w9chDL5by1fVQ/N2FPpmL6SwLswTZkGUfXNDnAk/H82ilVO62oy5hZ8KaRu OsXJgrKn/02LDtIGs2dErMz/Xm62Qw5RikfQFgd9ILpgPHQVjUd0Ca+NiFC0tMiwf1M3TzX10oy 2yJ9a35fdQZVecuk8gGwNztfDXC23g11XjYUzukzr8/UWRzywluZ14HPZn9o6W5mhLO1LYimTiH VlMKHqHyUtOyQ6p4LP/hQInN6A7D47XFx6TIgiMk7ZVKHIQJQQY/ViRDDdrAeAKPp1gZo+xW/Xl 4bOBdBlhIm48CYKt1te/GksCvwE2aAcqV8I5r9hMUrrkDYNxK7UEYiKWGPsQ53aALJMQJSA5XDi GxVnZA+oOSsx9RzjngNovD1jQjVKTOGiL86/RdGb4XjSoqtZBX949dgVrJgW8bWMUvo9a3r5uy+ ldnSR7x9fOoPEo2o1Cge0zxUDTim5d/ze7bCnukyq16eD+03/qtca55aDF45XNeEjR6hpoqERA7 9JRoT/7cP19VcrIwkeZZwE6R8oqhoQUcNdxjMVkbxpWASF76Ml63W3g58rOQphacvZGhixvI2tO gwE7QuRGxSCGpSYFerpnwT0LxJnhUo+JtZUCQR7AlZC7pGrkFNCOJChGHYLZQfCP/45/0U7y8AC OtZo8io7bnV4TnQ== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C57631C000D X-Stat-Signature: iqepcbjy8rchtj8satfskbkaemocppkf X-HE-Tag: 1771932034-657714 X-HE-Meta: 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 wQKKnhRn +h8POqi/FdqttYZvfuvZpaYop+OAdVYl08UhI991oX/jy/n8bFMhE2xBAW/+gvHiVDjusq7yYgr5t/AI/jGPTu7uQJdSkUen/WQYGG4ZnjqvunJn6aizUQyLrcPSA5kY+6iRd1Zy/PucBDaD2xRgOUGietqp68AY2kgLrTCIGnzJ7uw33VWrRDJTvKakaEqLthVybqrK+e5k9ve4jCAWvaUdjRZaew3GmJIF6xV2rqNx2WsMemIG/AhAcaA5yFqTyCeYlikIKkqORvU8YAG1g2gC4D0SXjwQIE8b14btU5Dt3U6WIoOhDMEbLiTr7tctUEmJtpJ8wd84Uoilo2jqA+ftodCueaOOqlyAnalScgFRClCyrt8+KvVjOLmT7SJuGnyzE 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: 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 bf3bed7e2d3fe..e21f02ae47b72 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::{ @@ -83,7 +88,7 @@ pub const fn page_align(addr: usize) -> usize { /// /// [`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`. @@ -93,7 +98,9 @@ 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`. @@ -105,7 +112,8 @@ 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() } } } @@ -126,8 +134,9 @@ 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 @@ -161,19 +170,20 @@ 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. @@ -348,10 +358,12 @@ 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