linux-kernel - Re: [RFC PATCH v2 3/3] mm: make generic pXd_addr

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Date:   Tue, 8 Sep 2020 19:20:20 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-mm <linux-mm@...ck.org>, Paul Mackerras <paulus@...ba.org>,
        linux-sparc <sparclinux@...r.kernel.org>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Richard Weinberger <richard@....at>,
        linux-x86 <x86@...nel.org>, Russell King <linux@...linux.org.uk>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>, Jeff Dike <jdike@...toit.com>,
        linux-um <linux-um@...ts.infradead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm <linux-arm-kernel@...ts.infradead.org>,
        linux-power <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: [RFC PATCH v2 3/3] mm: make generic pXd_addr_end() macros inline
 functions



Le 08/09/2020 à 17:48, Alexander Gordeev a écrit :
> On Tue, Sep 08, 2020 at 07:19:38AM +0200, Christophe Leroy wrote:
> 
> [...]
> 
>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>>> index 67ebc22cf83d..d9e7d16c2263 100644
>>> --- a/include/linux/pgtable.h
>>> +++ b/include/linux/pgtable.h
>>> @@ -656,31 +656,35 @@ static inline int arch_unmap_one(struct mm_struct *mm,
>>>    */
>>>   #ifndef pgd_addr_end
>>> -#define pgd_addr_end(pgd, addr, end)					\
>>> -({	unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK;	\
>>> -	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
>>> -})
>>> +#define pgd_addr_end pgd_addr_end
>>
>> I think that #define is pointless, usually there is no such #define
>> for the default case.
> 
> Default pgd_addr_end() gets overriden on s390 (arch/s390/include/asm/pgtable.h):
> 
> #define pgd_addr_end pgd_addr_end
> static inline unsigned long pgd_addr_end(pgd_t pgd, unsigned long addr, unsigned long end)
> {
> 	return rste_addr_end_folded(pgd_val(pgd), addr, end);
> }

Yes, there in s390 the #define is needed to hit the #ifndef pgd_addr_end 
that's in include/linux/pgtable.h

But in include/linux/pgtable.h, there is no need of an #define 
pgd_addr_end pgd_addr_end I think

> 
>>> +static inline unsigned long pgd_addr_end(pgd_t pgd, unsigned long addr, unsigned long end)
>>> +{	unsigned long __boundary = (addr + PGDIR_SIZE) & PGDIR_MASK;
>>> +	return (__boundary - 1 < end - 1) ? __boundary : end;
>>> +}


Christophe