linux-kernel - Re: [PATCH 1/3] kunit: test: Delete pointless resource API usage

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Message-ID: <CABVgOSn8UjWjEe-FNfOBSpZiBL0797VvJQZOOGp5QB6tv52COQ@mail.gmail.com>
Date: Mon, 5 Jan 2026 17:56:05 +0800
From: David Gow <davidgow@...gle.com>
To: Brendan Jackman <jackmanb@...gle.com>
Cc: Brendan Higgins <brendan.higgins@...ux.dev>, Rae Moar <raemoar63@...il.com>, 
	Kees Cook <kees@...nel.org>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	David Hildenbrand <david@...nel.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/3] kunit: test: Delete pointless resource API usage

On Wed, 24 Dec 2025 at 00:18, Brendan Jackman <jackmanb@...gle.com> wrote:
>
> This code uses the low-level resource API to track parameters of the
> vm_mmap call, but it doesn't do anything with them, because the mm
> teardown code takes care of tearing down the mmaps. Delete it.
>
> Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
> ---

This makes sense. Maybe there's a case where tracking mmaps as
resources could be useful in the future, but I can't think of any off
the top of my head, so this is just wasteful for now.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David



>  lib/kunit/user_alloc.c | 76 ++++----------------------------------------------
>  1 file changed, 6 insertions(+), 70 deletions(-)
>
> diff --git a/lib/kunit/user_alloc.c b/lib/kunit/user_alloc.c
> index b8cac765e6204..564f5566641d5 100644
> --- a/lib/kunit/user_alloc.c
> +++ b/lib/kunit/user_alloc.c
> @@ -7,21 +7,6 @@
>  #include <linux/kthread.h>
>  #include <linux/mm.h>
>
> -struct kunit_vm_mmap_resource {
> -       unsigned long addr;
> -       size_t size;
> -};
> -
> -/* vm_mmap() arguments */
> -struct kunit_vm_mmap_params {
> -       struct file *file;
> -       unsigned long addr;
> -       unsigned long len;
> -       unsigned long prot;
> -       unsigned long flag;
> -       unsigned long offset;
> -};
> -
>  int kunit_attach_mm(void)
>  {
>         struct mm_struct *mm;
> @@ -50,67 +35,18 @@ int kunit_attach_mm(void)
>  }
>  EXPORT_SYMBOL_GPL(kunit_attach_mm);
>
> -static int kunit_vm_mmap_init(struct kunit_resource *res, void *context)
> -{
> -       struct kunit_vm_mmap_params *p = context;
> -       struct kunit_vm_mmap_resource vres;
> -       int ret;
> -
> -       ret = kunit_attach_mm();
> -       if (ret)
> -               return ret;
> -
> -       vres.size = p->len;
> -       vres.addr = vm_mmap(p->file, p->addr, p->len, p->prot, p->flag, p->offset);
> -       if (!vres.addr)
> -               return -ENOMEM;
> -       res->data = kmemdup(&vres, sizeof(vres), GFP_KERNEL);
> -       if (!res->data) {
> -               vm_munmap(vres.addr, vres.size);
> -               return -ENOMEM;
> -       }
> -
> -       return 0;
> -}
> -
> -static void kunit_vm_mmap_free(struct kunit_resource *res)
> -{
> -       struct kunit_vm_mmap_resource *vres = res->data;
> -
> -       /*
> -        * Since this is executed from the test monitoring process,
> -        * the test's mm has already been torn down. We don't need
> -        * to run vm_munmap(vres->addr, vres->size), only clean up
> -        * the vres.
> -        */
> -
> -       kfree(vres);
> -       res->data = NULL;
> -}
> -
>  unsigned long kunit_vm_mmap(struct kunit *test, struct file *file,
>                             unsigned long addr, unsigned long len,
>                             unsigned long prot, unsigned long flag,
>                             unsigned long offset)
>  {
> -       struct kunit_vm_mmap_params params = {
> -               .file = file,
> -               .addr = addr,
> -               .len = len,
> -               .prot = prot,
> -               .flag = flag,
> -               .offset = offset,
> -       };
> -       struct kunit_vm_mmap_resource *vres;
> +       int err;
>
> -       vres = kunit_alloc_resource(test,
> -                                   kunit_vm_mmap_init,
> -                                   kunit_vm_mmap_free,
> -                                   GFP_KERNEL,
> -                                   &params);
> -       if (vres)
> -               return vres->addr;
> -       return 0;
> +       err = kunit_attach_mm();
> +       if (err)
> +               return err;
> +
> +       return vm_mmap(file, addr, len, prot, flag, offset);
>  }
>  EXPORT_SYMBOL_GPL(kunit_vm_mmap);
>
>
> --
> 2.51.2
>

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