From: Uladzislau Rezki <urezki@gmail.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-s390@vger.kernel.org, frankja@linux.ibm.com,
borntraeger@de.ibm.com, cohuck@redhat.com, david@redhat.com,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Nicholas Piggin <npiggin@gmail.com>,
Uladzislau Rezki <urezki@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
David Rientjes <rientjes@google.com>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v3 1/2] mm/vmalloc: add vmalloc_no_huge
Date: Thu, 10 Jun 2021 21:31:55 +0200 [thread overview]
Message-ID: <20210610193155.GA1854@pc638.lan> (raw)
In-Reply-To: <20210610154220.529122-2-imbrenda@linux.ibm.com>
Hello.
See below a small nit:
> The recent patches to add support for hugepage vmalloc mappings added a
> flag for __vmalloc_node_range to allow to request small pages.
> This flag is not accessible when calling vmalloc, the only option is to
> call directly __vmalloc_node_range, which is not exported.
>
> This means that a module can't vmalloc memory with small pages.
>
> Case in point: KVM on s390x needs to vmalloc a large area, and it needs
> to be mapped with small pages, because of a hardware limitation.
>
> This patch adds the function vmalloc_no_huge, which works like vmalloc,
> but it is guaranteed to always back the mapping using small pages. This
> function is exported, therefore it is usable by modules.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> ---
> include/linux/vmalloc.h | 1 +
> mm/vmalloc.c | 16 ++++++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 4d668abb6391..bfaaf0b6fa76 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
> const void *caller);
> void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
> int node, const void *caller);
> +void *vmalloc_no_huge(unsigned long size);
>
> extern void vfree(const void *addr);
> extern void vfree_atomic(const void *addr);
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a13ac524f6ff..296a2fcc3fbe 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size)
> }
> EXPORT_SYMBOL(vmalloc);
>
> +/**
> + * vmalloc_no_huge - allocate virtually contiguous memory using small pages
> + * @size: allocation size
> + *
You state that it allocates using "small pages". I think it might be confused
for people because of that vague meaning. The comment should be improved, imho,
saying rather about order-0 pages what we call "small pages".
> + * Allocate enough non-huge pages to cover @size from the page level
> + * allocator and map them into contiguous kernel virtual space.
> + *
> + * Return: pointer to the allocated memory or %NULL on error
> + */
> +void *vmalloc_no_huge(unsigned long size)
> +{
> + return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
> + VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));
> +}
> +EXPORT_SYMBOL(vmalloc_no_huge);
> +
> /**
> * vzalloc - allocate virtually contiguous memory with zero fill
> * @size: allocation size
> --
> 2.31.1
>
anyone looks good to me, please use:
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Thanks.
--
Vlad Rezki
next prev parent reply other threads:[~2021-06-10 19:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 15:42 [PATCH v3 0/2] mm: add vmalloc_no_huge and use it Claudio Imbrenda
2021-06-10 15:42 ` [PATCH v3 1/2] mm/vmalloc: add vmalloc_no_huge Claudio Imbrenda
2021-06-10 19:31 ` Uladzislau Rezki [this message]
2021-06-10 21:09 ` Andrew Morton
2021-06-11 8:23 ` Claudio Imbrenda
2021-06-14 2:01 ` Nicholas Piggin
2021-06-10 15:42 ` [PATCH v3 2/2] KVM: s390: fix for hugepage vmalloc Claudio Imbrenda
2021-06-10 15:56 ` Christian Borntraeger
2021-06-10 16:49 ` Claudio Imbrenda
2021-06-10 16:52 ` Christian Borntraeger
2021-06-14 1:43 ` Nicholas Piggin
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