linux-kernel - [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user

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Date:   Wed, 16 Sep 2020 06:57:10 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Eric Sandeen <esandeen@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        "Kani, Toshi" <toshi.kani@....com>,
        "Norton, Scott J" <scott.norton@....com>,
        "Tadakamadla, Rajesh (DCIG/CDI/HPS Perf)" 
        <rajesh.tadakamadla@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>
Subject: [PATCH] pmem: export the symbols __copy_user_flushcache and
 __copy_from_user_flushcache



On Tue, 15 Sep 2020, Mikulas Patocka wrote:

> 
> 
> On Tue, 15 Sep 2020, Mikulas Patocka wrote:
> 
> > > > - __copy_from_user_inatomic_nocache doesn't flush cache for leading and
> > > > trailing bytes.
> > > 
> > > You want copy_user_flushcache(). See how fs/dax.c arranges for
> > > dax_copy_from_iter() to route to pmem_copy_from_iter().
> > 
> > Is it something new for the kernel 5.10? I see only __copy_user_flushcache 
> > that is implemented just for x86 and arm64.
> > 
> > There is __copy_from_user_flushcache implemented for x86, arm64 and power. 
> > It is used in lib/iov_iter.c under
> > #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE - so should I use this?
> > 
> > Mikulas
> 
> ... and __copy_user_flushcache is not exported for modules. So, I am stuck 
> with __copy_from_user_inatomic_nocache.
> 
> Mikulas

I'm submitting this patch that adds the required exports (so that we could 
use __copy_from_user_flushcache on x86, arm64 and powerpc). Please, queue 
it for the next merge window.


From: Mikulas Patocka <mpatocka@...hat.com>

Export the symbols __copy_user_flushcache and __copy_from_user_flushcache,
so that modules can use this functionality.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

---
 arch/arm64/lib/uaccess_flushcache.c |    1 +
 arch/powerpc/lib/pmem.c             |    1 +
 arch/x86/lib/usercopy_64.c          |    1 +
 3 files changed, 3 insertions(+)

Index: linux-2.6/arch/arm64/lib/uaccess_flushcache.c
===================================================================
--- linux-2.6.orig/arch/arm64/lib/uaccess_flushcache.c	2020-09-16 12:44:15.068038000 +0200
+++ linux-2.6/arch/arm64/lib/uaccess_flushcache.c	2020-09-16 12:44:15.068038000 +0200
@@ -38,3 +38,4 @@ unsigned long __copy_user_flushcache(voi
 	__clean_dcache_area_pop(to, n - rc);
 	return rc;
 }
+EXPORT_SYMBOL_GPL(__copy_user_flushcache);
Index: linux-2.6/arch/x86/lib/usercopy_64.c
===================================================================
--- linux-2.6.orig/arch/x86/lib/usercopy_64.c	2020-09-16 12:44:15.068038000 +0200
+++ linux-2.6/arch/x86/lib/usercopy_64.c	2020-09-16 12:44:15.068038000 +0200
@@ -134,6 +134,7 @@ long __copy_user_flushcache(void *dst, c
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(__copy_user_flushcache);
 
 void __memcpy_flushcache(void *_dst, const void *_src, size_t size)
 {
Index: linux-2.6/arch/powerpc/lib/pmem.c
===================================================================
--- linux-2.6.orig/arch/powerpc/lib/pmem.c	2020-09-16 12:44:15.068038000 +0200
+++ linux-2.6/arch/powerpc/lib/pmem.c	2020-09-16 12:44:15.068038000 +0200
@@ -75,6 +75,7 @@ long __copy_from_user_flushcache(void *d
 
 	return copied;
 }
+EXPORT_SYMBOL_GPL(__copy_from_user_flushcache);
 
 void memcpy_flushcache(void *dest, const void *src, size_t size)
 {