Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings

From: Nicholas Piggin <npiggin@gmail.com>
To: linux-mm@kvack.org, Zefan Li <lizefan@huawei.com>
Cc: "Borislav\
	 Petkov" <bp@alien8.de>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	"Ingo Molnar" <mingo@redhat.com>,
	"Thomas\
	 Gleixner" <tglx@linutronix.de>, "Will Deacon" <will@kernel.org>,
	x86@kernel.org
Subject: Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings
Date: Mon, 20 Jul 2020 12:49:02 +1000	[thread overview]
Message-ID: <1595213278.m30kayfsvu.astroid@bobo.none> (raw)
In-Reply-To: <0e43e743-7c78-fb86-6c36-f42e6184d32c@huawei.com>

Excerpts from Zefan Li's message of July 20, 2020 12:02 pm:
>> +static int vmap_pages_range_noflush(unsigned long start, unsigned long end,
>> +				    pgprot_t prot, struct page **pages,
>> +				    unsigned int page_shift)
>> +{
>> +	if (page_shift == PAGE_SIZE) {
> 
> Is this a typo of PAGE_SHIFT?

Oh good catch, yeah that'll always be going via the one-at-a-time route 
and slow down the small page vmaps. Will fix.

Thanks,
Nick

> 
>> +		return vmap_small_pages_range_noflush(start, end, prot, pages);
>> +	} else {
>> +		unsigned long addr = start;
>> +		unsigned int i, nr = (end - start) >> page_shift;
>> +
>> +		for (i = 0; i < nr; i++) {
>> +			int err;
>> +
>> +			err = vmap_range_noflush(addr,
>> +					addr + (1UL << page_shift),
>> +					__pa(page_address(pages[i])), prot,
>> +					page_shift);
>> +			if (err)
>> +				return err;
>> +
>> +			addr += 1UL << page_shift;
>> +		}
>> +
>> +		return 0;
>> +	}
>> +}
>> +
> 