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From: Yury Norov <yury.norov@gmail.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Nicholas Piggin <npiggin@gmail.com>,
	Ding Tianhong <dingtianhong@huawei.com>,
	 Alexey Klimov <aklimov@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	 linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	 Uladzislau Rezki <urezki@gmail.com>
Subject: Re: [PATCH] vmap(): don't allow invalid pages
Date: Thu, 20 Jan 2022 18:56:16 -0800	[thread overview]
Message-ID: <CAAH8bW_wL7=7+Jj6vXmQSe_az0BvS_otxhBe4LOKU5fcJV9aXQ@mail.gmail.com> (raw)
In-Reply-To: <5b62ed03-8da8-a94d-cc48-a8cac1eae1c9@arm.com>

On Wed, Jan 19, 2022 at 7:37 PM Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
>
>
> On 1/19/22 10:52 PM, Yury Norov wrote:
> >> Why should not this just scan over the entire user provided struct page
> >> array and make sure that all pages there in are valid via above method,
> >> but in vmap() itself before calling vmap_pages_range(). Because seems
> >> like a single invalid page detected in vmap_pages_pte_range() will
> >> anyways abort the entire vmap(). This will also enable us to drop the
> >> existing NULL check above.
> >
> > I can do this, but why is it any better than the current approach?
>
> Because it will just return on the first instance where the valid page
> check fails, saving us some CPU cycles and an incomplete mapping ?

This should normally never happen, that's why warn_on() is there. If it
happens, there is a serious problem, and the code must be fixed. So,
no CPU cycles saving in real life.


  parent reply	other threads:[~2022-01-21  2:56 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-18 23:52 [PATCH] vmap(): don't allow invalid pages Yury Norov
2022-01-19  0:51 ` Matthew Wilcox
2022-01-19  6:17   ` Anshuman Khandual
2022-01-19 17:22     ` Yury Norov
2022-01-20  3:37       ` Anshuman Khandual
2022-01-20  4:27         ` Matthew Wilcox
2022-01-21  2:56         ` Yury Norov [this message]
2022-01-19 11:16 ` Mark Rutland
2022-01-19 17:00   ` Yury Norov
2022-01-19 18:06     ` Mark Rutland
2022-01-19 13:28 ` Robin Murphy
2022-01-19 16:27   ` Matthew Wilcox
2022-01-19 17:54     ` Russell King (Oracle)
2022-01-19 18:01       ` Matthew Wilcox
2022-01-19 18:57         ` Russell King (Oracle)
2022-01-19 19:35           ` Matthew Wilcox
2022-01-19 22:38             ` Russell King (Oracle)
2022-01-19 18:43     ` Robin Murphy
2022-01-19 19:12       ` Russell King (Oracle)
2022-01-20 12:22         ` Robin Murphy
2022-01-20 13:03           ` Russell King (Oracle)
2022-01-20 16:37             ` Robin Murphy
2022-01-20 16:54               ` Russell King (Oracle)
2022-01-20 19:04                 ` Matthew Wilcox
2022-01-21  5:26               ` Yury Norov
2022-01-26  2:50   ` Matthew Wilcox

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