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Howlett" , Lyude Paul , David Airlie , Simona Vetter , Greg Kroah-Hartman , "Rafael J. Wysocki" , Sami Tolvanen , rust-for-linux@vger.kernel.org, linux-mm@kvack.org, dri-devel@lists.freedesktop.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, Alvin Sun Subject: Re: [PATCH v4 02/11] rust: mm: add `task_size` helper Message-ID: References: <20261020-tyr-ioctls-v4-0-704de77da223@kylinos.cn> <20261020-tyr-ioctls-v4-2-704de77da223@kylinos.cn> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261020-tyr-ioctls-v4-2-704de77da223@kylinos.cn> X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.13.1.5.4/292.705.96 On Tue, Oct 20, 2026 at 04:25:19PM +0800, Ke Sun wrote: > From: Alvin Sun I was testing Tyr's auto allocation for the user va range, and was surprised to see that mm.task_size() is always returning 0. It seems like it should work since it uses the task_size from struct mm_struct, but it doesn't, at least for me. If you look at tyr-dev, I think it would be better to use Sami's approach: 428d71932b6f rust: task: add task_size() Sami creates a task_size() method for CurrentTask which is our equivalent to the `current` global and then you can see that task_size becomes much more clearly the equivalent of "TASK_SIZE_OF" used by panthor. This approach also correctly returns a user va range when Tyr has to assign it in my tests, so let's switch over. > > Expose the task's address space size. It is used by the Tyr driver > for splitting a VM's GPU address space into user and kernel regions. > > Signed-off-by: Alvin Sun > Reviewed-by: Daniel Almeida > --- > rust/kernel/mm.rs | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs > index 4764d7b68f2a7..d2dfbb7d43972 100644 > --- a/rust/kernel/mm.rs > +++ b/rust/kernel/mm.rs > @@ -149,6 +149,13 @@ pub fn mmget_not_zero(&self) -> Option> { > None > } > } > + > + /// The size of the process virtual address space. > + #[inline] > + pub fn task_size(&self) -> usize { > + // SAFETY: `self.as_raw()` is a valid pointer to an `mm_struct` per the type invariants. > + unsafe { (*self.as_raw()).__bindgen_anon_1.task_size } > + } > } > > // These methods require `mm_users` to be non-zero. > > -- > 2.43.0 >