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Date: Mon, 14 Feb 2022 13:25:55 -0800
From: Todd Kjos <tkjos@...gle.com>
To: "T.J. Mercier" <tjmercier@...gle.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Jonathan Corbet <corbet@....net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Arve Hjønnevåg <arve@...roid.com>,
Todd Kjos <tkjos@...roid.com>,
Martijn Coenen <maco@...roid.com>,
Joel Fernandes <joel@...lfernandes.org>,
Christian Brauner <brauner@...nel.org>,
Hridya Valsaraju <hridya@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
Liam Mark <lmark@...eaurora.org>,
Brian Starkey <Brian.Starkey@....com>,
John Stultz <john.stultz@...aro.org>,
Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>, kaleshsingh@...gle.com,
Kenny.Ho@....com, dri-devel@...ts.freedesktop.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
cgroups@...r.kernel.org
Subject: Re: [RFC v2 6/6] android: binder: Add a buffer flag to relinquish
ownership of fds
On Fri, Feb 11, 2022 at 8:19 AM T.J. Mercier <tjmercier@...gle.com> wrote:
>
> This patch introduces a buffer flag BINDER_BUFFER_FLAG_SENDER_NO_NEED
> that a process sending an fd array to another process over binder IPC
> can set to relinquish ownership of the fds being sent for memory
> accounting purposes. If the flag is found to be set during the fd array
> translation and the fd is for a DMA-BUF, the buffer is uncharged from
> the sender's cgroup and charged to the receiving process's cgroup
> instead.
>
> It is up to the sending process to ensure that it closes the fds
> regardless of whether the transfer failed or succeeded.
>
> Most graphics shared memory allocations in Android are done by the
> graphics allocator HAL process. On requests from clients, the HAL process
> allocates memory and sends the fds to the clients over binder IPC.
> The graphics allocator HAL will not retain any references to the
> buffers. When the HAL sets the BINDER_BUFFER_FLAG_SENDER_NO_NEED for fd
> arrays holding DMA-BUF fds, the gpu cgroup controller will be able to
> correctly charge the buffers to the client processes instead of the
> graphics allocator HAL.
>
> From: Hridya Valsaraju <hridya@...gle.com>
> Signed-off-by: Hridya Valsaraju <hridya@...gle.com>
> Co-developed-by: T.J. Mercier <tjmercier@...gle.com>
> Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
> ---
> changes in v2
> - Move dma-buf cgroup charge transfer from a dma_buf_op defined by every
> heap to a single dma-buf function for all heaps per Daniel Vetter and
> Christian König.
>
> drivers/android/binder.c | 26 ++++++++++++++++++++++++++
> include/uapi/linux/android/binder.h | 1 +
> 2 files changed, 27 insertions(+)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 8351c5638880..f50d88ded188 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -42,6 +42,7 @@
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> +#include <linux/dma-buf.h>
> #include <linux/fdtable.h>
> #include <linux/file.h>
> #include <linux/freezer.h>
> @@ -2482,8 +2483,10 @@ static int binder_translate_fd_array(struct list_head *pf_head,
Is this only needed for the BINDER_TYPE_FDA case (multiple fds)? This
never needs to be done in the BINDER_TYPE_FD case (single fd)?
> {
> binder_size_t fdi, fd_buf_size;
> binder_size_t fda_offset;
> + bool transfer_gpu_charge = false;
> const void __user *sender_ufda_base;
> struct binder_proc *proc = thread->proc;
> + struct binder_proc *target_proc = t->to_proc;
> int ret;
>
> fd_buf_size = sizeof(u32) * fda->num_fds;
> @@ -2521,8 +2524,15 @@ static int binder_translate_fd_array(struct list_head *pf_head,
> if (ret)
> return ret;
>
> + if (IS_ENABLED(CONFIG_CGROUP_GPU) &&
> + parent->flags & BINDER_BUFFER_FLAG_SENDER_NO_NEED)
> + transfer_gpu_charge = true;
> +
> for (fdi = 0; fdi < fda->num_fds; fdi++) {
> u32 fd;
> + struct dma_buf *dmabuf;
> + struct gpucg *gpucg;
> +
> binder_size_t offset = fda_offset + fdi * sizeof(fd);
> binder_size_t sender_uoffset = fdi * sizeof(fd);
>
> @@ -2532,6 +2542,22 @@ static int binder_translate_fd_array(struct list_head *pf_head,
> in_reply_to);
> if (ret)
> return ret > 0 ? -EINVAL : ret;
> +
> + if (!transfer_gpu_charge)
> + continue;
> +
> + dmabuf = dma_buf_get(fd);
> + if (IS_ERR(dmabuf))
> + continue;
> +
> + gpucg = gpucg_get(target_proc->tsk);
> + ret = dma_buf_charge_transfer(dmabuf, gpucg);
> + if (ret) {
> + pr_warn("%d:%d Unable to transfer DMA-BUF fd charge to %d",
> + proc->pid, thread->pid, target_proc->pid);
> + gpucg_put(gpucg);
> + }
> + dma_buf_put(dmabuf);
> }
> return 0;
> }
> diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h
> index 3246f2c74696..169fd5069a1a 100644
> --- a/include/uapi/linux/android/binder.h
> +++ b/include/uapi/linux/android/binder.h
> @@ -137,6 +137,7 @@ struct binder_buffer_object {
>
> enum {
> BINDER_BUFFER_FLAG_HAS_PARENT = 0x01,
> + BINDER_BUFFER_FLAG_SENDER_NO_NEED = 0x02,
> };
>
> /* struct binder_fd_array_object - object describing an array of fds in a buffer
> --
> 2.35.1.265.g69c8d7142f-goog
>
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