linux-kernel - Re: [PATCH V3 13/15] parisc/kmap: Remove duplicate kmap code

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Date:   Thu, 7 May 2020 13:52:58 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     ira.weiny@...el.com
Cc:     linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, dri-devel@...ts.freedesktop.org,
        Christian Koenig <christian.koenig@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH V3 13/15] parisc/kmap: Remove duplicate kmap code

On Thu,  7 May 2020 08:00:01 -0700 ira.weiny@...el.com wrote:

> parisc reimplements the kmap calls except to flush it's dcache.  This is
> arguably an abuse of kmap but regardless it is messy and confusing.
> 
> Remove the duplicate code and have parisc define
> ARCH_HAS_FLUSH_ON_KUNMAP for a kunmap_flush_on_unmap() architecture
> specific call to flush the cache.

checkpatch says:

ERROR: #define of 'ARCH_HAS_FLUSH_ON_KUNMAP' is wrong - use Kconfig variables or standard guards instead
#69: FILE: arch/parisc/include/asm/cacheflush.h:103:
+#define ARCH_HAS_FLUSH_ON_KUNMAP

which is fair enough, I guess.  More conventional would be

arch/parisc/include/asm/cacheflush.h:

static inline void kunmap_flush_on_unmap(void *addr)
{
	...
}
#define kunmap_flush_on_unmap kunmap_flush_on_unmap


include/linux/highmem.h:

#ifndef kunmap_flush_on_unmap
static inline void kunmap_flush_on_unmap(void *addr)
{
}
#define kunmap_flush_on_unmap kunmap_flush_on_unmap
#endif


static inline void kunmap_atomic_high(void *addr)
{
	/* Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic()
	 * handles re-enabling faults + preemption */
	kunmap_flush_on_unmap(addr);
}


but I don't really think it's worth bothering changing it.	

(Ditto patch 3/15)