mm/mmu_notifier: use structure for invalidate_range_start/end calls v2

To avoid having to change many call sites everytime we want to add a
parameter use a structure to group all parameters for the mmu_notifier
invalidate_range_start/end cakks.  No functional changes with this patch.

[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20181205053628.3210-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
From: Jérôme Glisse <jglisse@redhat.com>
Subject: mm/mmu_notifier: use structure for invalidate_range_start/end calls v3

fix build warning in migrate.c when CONFIG_MMU_NOTIFIER=n

Link: http://lkml.kernel.org/r/20181213171330.8489-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/dax.c b/fs/dax.c
index 48132ec..262e14f 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -779,7 +779,8 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 
 	i_mmap_lock_read(mapping);
 	vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) {
-		unsigned long address, start, end;
+		struct mmu_notifier_range range;
+		unsigned long address;
 
 		cond_resched();
 
@@ -793,7 +794,8 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 		 * call mmu_notifier_invalidate_range_start() on our behalf
 		 * before taking any lock.
 		 */
-		if (follow_pte_pmd(vma->vm_mm, address, &start, &end, &ptep, &pmdp, &ptl))
+		if (follow_pte_pmd(vma->vm_mm, address, &range,
+				   &ptep, &pmdp, &ptl))
 			continue;
 
 		/*
@@ -835,7 +837,7 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 			pte_unmap_unlock(ptep, ptl);
 		}
 
-		mmu_notifier_invalidate_range_end(vma->vm_mm, start, end);
+		mmu_notifier_invalidate_range_end(&range);
 	}
 	i_mmap_unlock_read(mapping);
 }