linux-kernel - Re: [PATCH 17/21] binder: malloc new

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Message-ID: <20231107090838.260730-1-aliceryhl@google.com>
Date:   Tue,  7 Nov 2023 09:08:38 +0000
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     Carlos Llamas <cmllamas@...gle.com>
Cc:     "Arve Hjønnevåg" <arve@...roid.com>,
        Christian Brauner <brauner@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        Martijn Coenen <maco@...roid.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...roid.com>
Subject: Re: [PATCH 17/21] binder: malloc new_buffer outside of locks

Carlos Llamas <cmllamas@...gle.com> writes:
> Preallocate new_buffer before acquiring the alloc->mutex and hand it
> down to binder_alloc_new_buf_locked(). The new buffer will be used in
> the vast majority of requests (measured at 98.2% in field data). The
> buffer is discarded otherwise. This change is required in preparation
> for transitioning alloc->mutex into a spinlock in subsequent commits.
> 
> Signed-off-by: Carlos Llamas <cmllamas@...gle.com>

You also need to free the new buffer here:

	if (unlikely(!best_fit)) {
		binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
				   "%d: binder_alloc_buf size %zd failed, no address space\n",
				   alloc->pid, size);
		debug_no_space_locked(alloc);
		return ERR_PTR(-ENOSPC);
	}

Other than the above, this looks correct to me.

Alice