dax: remove VM_MIXEDMAP for fsdax and device dax

This patch is reworked from an earlier patch that Dan has posted:
https://patchwork.kernel.org/patch/10131727/

VM_MIXEDMAP is used by dax to direct mm paths like vm_normal_page() that
the memory page it is dealing with is not typical memory from the linear
map.  The get_user_pages_fast() path, since it does not resolve the vma,
is already using {pte,pmd}_devmap() as a stand-in for VM_MIXEDMAP, so we
use that as a VM_MIXEDMAP replacement in some locations.  In the cases
where there is no pte to consult we fallback to using vma_is_dax() to
detect the VM_MIXEDMAP special case.

Now that we have explicit driver pfn_t-flag opt-in/opt-out for
get_user_pages() support for DAX we can stop setting VM_MIXEDMAP.  This
also means we no longer need to worry about safely manipulating vm_flags
in a future where we support dynamically changing the dax mode of a
file.

DAX should also now be supported with madvise_behavior(), vma_merge(),
and copy_page_range().

This patch has been tested against ndctl unit test.  It has also been
tested against xfstests commit: 625515d using fake pmem created by
memmap and no additional issues have been observed.

Link: http://lkml.kernel.org/r/152847720311.55924.16999195879201817653.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

7 files changed, 24 insertions, 10 deletions

diff --git a/mm/hmm.c b/mm/hmm.c
index de7b6bf77201..f40e8add84b5 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -676,7 +676,8 @@ int hmm_vma_get_pfns(struct hmm_range *range)
 		return -EINVAL;
 
 	/* FIXME support hugetlb fs */
-	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
+			vma_is_dax(vma)) {
 		hmm_pfns_special(range);
 		return -EINVAL;
 	}
@@ -849,7 +850,8 @@ int hmm_vma_fault(struct hmm_range *range, bool block)
 		return -EINVAL;
 
 	/* FIXME support hugetlb fs */
-	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+	if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
+			vma_is_dax(vma)) {
 		hmm_pfns_special(range);
 		return -EINVAL;
 	}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a9e1e093df51..1ce44e87f494 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -762,11 +762,11 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 	 * but we need to be consistent with PTEs and architectures that
 	 * can't support a 'special' bit.
 	 */
-	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
+	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+			!pfn_t_devmap(pfn));
 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 						(VM_PFNMAP|VM_MIXEDMAP));
 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
-	BUG_ON(!pfn_t_devmap(pfn));
 
 	if (addr < vma->vm_start || addr >= vma->vm_end)
 		return VM_FAULT_SIGBUS;
diff --git a/mm/ksm.c b/mm/ksm.c
index a6d43cf9a982..9b855a8b0f2d 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2430,6 +2430,9 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 				 VM_HUGETLB | VM_MIXEDMAP))
 			return 0;		/* just ignore the advice */
 
+		if (vma_is_dax(vma))
+			return 0;
+
 #ifdef VM_SAO
 		if (*vm_flags & VM_SAO)
 			return 0;
diff --git a/mm/memory.c b/mm/memory.c
index 348279ff6e51..7c3bd119fcca 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -859,6 +859,10 @@ struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 				return NULL;
 			}
 		}
+
+		if (pte_devmap(pte))
+			return NULL;
+
 		print_bad_pte(vma, addr, pte, NULL);
 		return NULL;
 	}
@@ -923,6 +927,8 @@ struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
 		}
 	}
 
+	if (pmd_devmap(pmd))
+		return NULL;
 	if (is_zero_pfn(pfn))
 		return NULL;
 	if (unlikely(pfn > highest_memmap_pfn))
diff --git a/mm/migrate.c b/mm/migrate.c
index 8c0af0f7cab1..4a83268e23c2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2951,7 +2951,8 @@ int migrate_vma(const struct migrate_vma_ops *ops,
 	/* Sanity check the arguments */
 	start &= PAGE_MASK;
 	end &= PAGE_MASK;
-	if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL))
+	if (!vma || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL) ||
+			vma_is_dax(vma))
 		return -EINVAL;
 	if (start < vma->vm_start || start >= vma->vm_end)
 		return -EINVAL;
diff --git a/mm/mlock.c b/mm/mlock.c
index 74e5a6547c3d..41cc47e28ad6 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -527,7 +527,8 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 	vm_flags_t old_flags = vma->vm_flags;
 
 	if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
-	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
+	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
+	    vma_is_dax(vma))
 		/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
 		goto out;
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 17bbf4d3e24f..8d6449e74431 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1796,11 +1796,12 @@ out:
 
 	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
-		if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
-					vma == get_gate_vma(current->mm)))
-			mm->locked_vm += (len >> PAGE_SHIFT);
-		else
+		if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
+					is_vm_hugetlb_page(vma) ||
+					vma == get_gate_vma(current->mm))
 			vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+		else
+			mm->locked_vm += (len >> PAGE_SHIFT);
 	}
 
 	if (file)