linux-kernel - Re: [PATCH v3 3/6] kunit: test: Export kunit_attach

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Message-ID: <CAFuZdDJ8tL4NDpFt+hVjyt0KcO15baeU-yf2RN4bHQRu9+XA6Q@mail.gmail.com>
Date: Mon, 14 Jul 2025 21:52:15 -0700
From: Carlos Llamas <cmllamas@...gle.com>
To: Tiffany Yang <ynaffit@...gle.com>
Cc: linux-kernel@...r.kernel.org, keescook@...gle.com, kernel-team@...roid.com, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arve Hjønnevåg <arve@...roid.com>, 
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joelagnelf@...dia.com>, Christian Brauner <brauner@...nel.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, Brendan Higgins <brendan.higgins@...ux.dev>, 
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, linux-kselftest@...r.kernel.org, 
	kunit-dev@...glegroups.com
Subject: Re: [PATCH v3 3/6] kunit: test: Export kunit_attach_mm()

On Mon, Jul 14, 2025 at 11:53:16AM -0700, Tiffany Yang wrote:
> Tests can allocate from virtual memory using kunit_vm_mmap(), which
> transparently creates and attaches an mm_struct to the test runner if
> one is not already attached. This is suitable for most cases, except for
> when the code under test must access a task's mm before performing an
> mmap. Expose kunit_attach_mm() as part of the interface for those
> cases. This does not change the existing behavior.
>
> Cc: David Gow <davidgow@...gle.com>
> Signed-off-by: Tiffany Yang <ynaffit@...gle.com>
> ---
>  include/kunit/test.h   | 12 ++++++++++++
>  lib/kunit/user_alloc.c |  4 ++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index 39c768f87dc9..d958ee53050e 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -531,6 +531,18 @@ static inline char *kunit_kstrdup(struct kunit *test, const char *str, gfp_t gfp
>   */
>  const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp);
>
> +/**
> + * kunit_attach_mm() - Create and attach a new mm if it doesn't already exist.
> + *
> + * Allocates a &struct mm_struct and attaches it to @current. In most cases, call
> + * kunit_vm_mmap() without calling kunit_attach_mm() directly. Only necessary when
> + * code under test accesses the mm before executing the mmap (e.g., to perform
> + * additional initialization beforehand).
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int kunit_attach_mm(void);
> +
>  /**
>   * kunit_vm_mmap() - Allocate KUnit-tracked vm_mmap() area
>   * @test: The test context object.
> diff --git a/lib/kunit/user_alloc.c b/lib/kunit/user_alloc.c
> index 46951be018be..b8cac765e620 100644
> --- a/lib/kunit/user_alloc.c
> +++ b/lib/kunit/user_alloc.c
> @@ -22,8 +22,7 @@ struct kunit_vm_mmap_params {
>       unsigned long offset;
>  };
>
> -/* Create and attach a new mm if it doesn't already exist. */
> -static int kunit_attach_mm(void)
> +int kunit_attach_mm(void)
>  {
>       struct mm_struct *mm;
>
> @@ -49,6 +48,7 @@ static int kunit_attach_mm(void)
>
>       return 0;
>  }
> +EXPORT_SYMBOL_GPL(kunit_attach_mm);
>
>  static int kunit_vm_mmap_init(struct kunit_resource *res, void *context)
>  {
> --
> 2.50.0.727.gbf7dc18ff4-goog
>

LGTM!

Reviewed-by: Carlos Llamas <cmllamas@...gle.com>