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Date:   Tue, 10 Jan 2023 11:44:51 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Guenter Roeck <linux@roeck-us.net>, Marco Elver <elver@google.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Kees Cook <kees@kernel.org>, Jaegeuk Kim <jaegeuk@kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        dalias@libc.org
Subject: Re: Linux 6.2-rc3
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 <20230109174742.GA1191249@roeck-us.net>
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On Mon, Jan 09, 2023 at 04:18:02PM -0600, Linus Torvalds wrote:

> > In file included from <command-line>:
> > In function 'follow_pmd_mask',
> >     inlined from 'follow_pud_mask' at mm/gup.c:735:9,
> >     inlined from 'follow_p4d_mask' at mm/gup.c:752:9,
> >     inlined from 'follow_page_mask' at mm/gup.c:809:9:
> > include/linux/compiler_types.h:358:45: error: call to '__compiletime_assert_263' declared with attribute error: Unsupported access size for {READ,WRITE}_ONCE().
> >   358 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> >
> > Bisect points to commit 0862ff059c9e ("sh/mm: Make pmd_t similar to pte_t").
> > This commit introduces
> >
> > -typedef struct { unsigned long long pmd; } pmd_t;
> > +typedef struct {
> > +       struct {
> > +               unsigned long pmd_low;
> > +               unsigned long pmd_high;
> > +       };
> > +       unsigned long long pmd;
> > +} pmd_t;
> >
> > That should probably be "typedef union", not "typedef struct".
> 
> Ok, PeterZ has been off due to the holidays, but seems back. I agree,

Yup, nearly 2 weeks of no email what so ever.. glorious!

> that outer 'struct' should obviously be 'union', but let's make the
> guilty party (ie Peter) fix it up.

Urgh.. yes. How did the robots not yell at me before.

So the original patch came in through x86/mm, but this is very much a SH
only fix how do we route this? Linus you want to take this directly or
Rich do you have an urgent queue for the next -rc somewhere?

---
Subject: sh/mm: Fix pmd_t for real

Because typing is hard...

Fixes: 0862ff059c9e ("sh/mm: Make pmd_t similar to pte_t")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
diff --git a/arch/sh/include/asm/pgtable-3level.h b/arch/sh/include/asm/pgtable-3level.h
index a889a3a938ba..d1ce73f3bd85 100644
--- a/arch/sh/include/asm/pgtable-3level.h
+++ b/arch/sh/include/asm/pgtable-3level.h
@@ -28,7 +28,7 @@
 #define pmd_ERROR(e) \
 	printk("%s:%d: bad pmd %016llx.\n", __FILE__, __LINE__, pmd_val(e))
 
-typedef struct {
+typedef union {
 	struct {
 		unsigned long pmd_low;
 		unsigned long pmd_high;