linux-kernel - [PATCH v2 2/4] dax: add stub for pmdp_huge_clear

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Date:   Thu, 22 Dec 2016 14:18:54 -0700
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Dave Hansen <dave.hansen@...el.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org
Subject: [PATCH v2 2/4] dax: add stub for pmdp_huge_clear_flush()

Add a pmdp_huge_clear_flush() stub for configs that don't define
CONFIG_TRANSPARENT_HUGEPAGE.

We use a WARN_ON_ONCE() instead of a BUILD_BUG() because in the DAX code at
least we do want this compile successfully even for configs without
CONFIG_TRANSPARENT_HUGEPAGE.  It'll be a runtime decision whether we call
this code gets called, based on whether we find DAX PMD entries in our
tree.  We shouldn't ever find such PMD entries for
!CONFIG_TRANSPARENT_HUGEPAGE configs, so this function should never be
called.

Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 include/asm-generic/pgtable.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 18af2bc..65e9536 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -178,9 +178,19 @@ extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
 #endif
 
 #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
 			      unsigned long address,
 			      pmd_t *pmdp);
+#else
+static inline pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
+			      unsigned long address,
+			      pmd_t *pmdp)
+{
+	WARN_ON_ONCE(1);
+	return *pmdp;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
 #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT
-- 
2.7.4