linux-kernel - Re: [PATCH v8 18/24] mm: Provide speculative fault infrastructure

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Message-ID: <5b16d6ce-6b62-e4ca-2d78-c25bb008e27e@oracle.com>
Date:   Mon, 26 Feb 2018 12:16:09 -0500
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Laurent Dufour <ldufour@...ux.vnet.ibm.com>,
        paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>,
        benh@...nel.crashing.org, mpe@...erman.id.au, paulus@...ba.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
        Will Deacon <will.deacon@....com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        kemi.wang@...el.com, sergey.senozhatsky.work@...il.com,
        Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v8 18/24] mm: Provide speculative fault infrastructure

Hi Laurent,

This series doesn't build for me[*] when CONFIG_TRANSPARENT_HUGEPAGE is unset.

The problem seems to be that the BUILD_BUG() version of pmd_same is called in pte_map_lock:

On 02/16/2018 10:25 AM, Laurent Dufour wrote:
> +static bool pte_map_lock(struct vm_fault *vmf)
> +{
...snip...
> +	if (!pmd_same(pmdval, vmf->orig_pmd))
> +		goto out;

Since SPF can now call pmd_same without THP, maybe the way to fix it is just

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 2cfa3075d148..e130692db24a 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -375,7 +375,8 @@ static inline int pte_unused(pte_t pte)
  #endif
  
  #ifndef __HAVE_ARCH_PMD_SAME
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || \
+    defined(CONFIG_SPECULATIVE_PAGE_FAULT)
  static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
  {
         return pmd_val(pmd_a) == pmd_val(pmd_b);

?

Daniel


[*]  The errors are:

In file included from /home/dmjordan/src/linux/include/linux/kernel.h:10:0,
                  from /home/dmjordan/src/linux/include/linux/list.h:9,
                  from /home/dmjordan/src/linux/include/linux/smp.h:12,
                  from /home/dmjordan/src/linux/include/linux/kernel_stat.h:5,
                  from /home/dmjordan/src/linux/mm/memory.c:41:
In function ‘pmd_same.isra.104’,
     inlined from ‘pte_map_lock’ at /home/dmjordan/src/linux/mm/memory.c:2380:7:
/home/dmjordan/src/linux/include/linux/compiler.h:324:38: error: call to ‘__compiletime_assert_391’ declared with attribute error: BUILD_BUG failed
   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                       ^
/home/dmjordan/src/linux/include/linux/compiler.h:304:4: note: in definition of macro ‘__compiletime_assert’
     prefix ## suffix();    \
     ^~~~~~
/home/dmjordan/src/linux/include/linux/compiler.h:324:2: note: in expansion of macro ‘_compiletime_assert’
   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
   ^~~~~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/linux/build_bug.h:45:37: note: in expansion of macro ‘compiletime_assert’
  #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                      ^~~~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/linux/build_bug.h:79:21: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
  #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
                      ^~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/asm-generic/pgtable.h:391:2: note: in expansion of macro ‘BUILD_BUG’
   BUILD_BUG();
   ^~~~~~~~~
   CC      block/elevator.o
   CC      crypto/crypto_wq.o
In function ‘pmd_same.isra.104’,
     inlined from ‘pte_spinlock’ at /home/dmjordan/src/linux/mm/memory.c:2326:7,
     inlined from ‘handle_pte_fault’ at /home/dmjordan/src/linux/mm/memory.c:4181:7:
/home/dmjordan/src/linux/include/linux/compiler.h:324:38: error: call to ‘__compiletime_assert_391’ declared with attribute error: BUILD_BUG failed
   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                       ^
/home/dmjordan/src/linux/include/linux/compiler.h:304:4: note: in definition of macro ‘__compiletime_assert’
     prefix ## suffix();    \
     ^~~~~~
/home/dmjordan/src/linux/include/linux/compiler.h:324:2: note: in expansion of macro ‘_compiletime_assert’
   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
   ^~~~~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/linux/build_bug.h:45:37: note: in expansion of macro ‘compiletime_assert’
  #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                      ^~~~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/linux/build_bug.h:79:21: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
  #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
                      ^~~~~~~~~~~~~~~~
/home/dmjordan/src/linux/include/asm-generic/pgtable.h:391:2: note: in expansion of macro ‘BUILD_BUG’
   BUILD_BUG();
   ^~~~~~~~~
...
make[2]: *** [/home/dmjordan/src/linux/scripts/Makefile.build:316: mm/memory.o] Error 1
make[1]: *** [/home/dmjordan/src/linux/Makefile:1047: mm] Error 2