[v2,2/8] mm,fs,dax: Change ->pmd_fault to ->huge_fault

Commit Message

Wilcox, Matthew R Jan. 5, 2016, 6:30 p.m. UTC

From: Matthew Wilcox <[e-mail]>

In preparation for adding the ability to handle PUD pages, convert
->pmd_fault to ->huge_fault.  huge_fault() takes a vm_fault structure
instead of separate (address, pmd, flags) parameters.  The vm_fault
structure is extended to include a union of the different page table
pointers that may be needed, and three flag bits are reserved to indicate
which type of pointer is in the union.

The DAX fault handlers are unified into one entry point, meaning that
the filesystems can be largely unconcerned with what size of fault they
are handling.  ext4 needs to know in order to reserve enough blocks in
the journal, but ext2 and xfs are oblivious.

The existing dax_fault and dax_mkwrite had no callers, so rename the
__dax_fault and __dax_mkwrite to lose the initial underscores.

Signed-off-by: Matthew Wilcox <[e-mail]>
---
 Documentation/filesystems/dax.txt | 12 +++--
 fs/block_dev.c                    | 10 +---
 fs/dax.c                          | 97 +++++++++++++--------------------------
 fs/ext2/file.c                    | 27 ++---------
 fs/ext4/file.c                    | 56 +++++++---------------
 fs/xfs/xfs_file.c                 | 25 +++++-----
 fs/xfs/xfs_trace.h                |  2 +-
 include/linux/dax.h               | 17 -------
 include/linux/mm.h                | 20 ++++++--
 mm/memory.c                       | 20 ++++++--
 10 files changed, 102 insertions(+), 184 deletions(-)

Patch

diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt
index 7bde640..2fe9e74 100644
--- a/Documentation/filesystems/dax.txt
+++ b/Documentation/filesystems/dax.txt
@@ -49,6 +49,7 @@  These block devices may be used for inspiration:
 - axonram: Axon DDR2 device driver
 - brd: RAM backed block device driver
 - dcssblk: s390 dcss block device driver
+- pmem: NV-DIMM Persistent Memory driver
 
 
 Implementation Tips for Filesystem Writers
@@ -61,9 +62,9 @@  Filesystem support consists of
   dax_do_io() instead of blockdev_direct_IO() if S_DAX is set
 - implementing an mmap file operation for DAX files which sets the
   VM_MIXEDMAP and VM_HUGEPAGE flags on the VMA, and setting the vm_ops to
-  include handlers for fault, pmd_fault and page_mkwrite (which should
-  probably call dax_fault(), dax_pmd_fault() and dax_mkwrite(), passing the
-  appropriate get_block() callback)
+  include handlers for fault, huge_fault and page_mkwrite (which should
+  probably call dax_fault() and dax_mkwrite(), passing the appropriate
+  get_block() callback)
 - calling dax_truncate_page() instead of block_truncate_page() for DAX files
 - calling dax_zero_page_range() instead of zero_user() for DAX files
 - ensuring that there is sufficient locking between reads, writes,
@@ -75,8 +76,9 @@  calls to get_block() (for example by a page-fault racing with a read()
 or a write()) work correctly.
 
 These filesystems may be used for inspiration:
-- ext2: the second extended filesystem, see Documentation/filesystems/ext2.txt
-- ext4: the fourth extended filesystem, see Documentation/filesystems/ext4.txt
+- ext2: see Documentation/filesystems/ext2.txt
+- ext4: see Documentation/filesystems/ext4.txt
+- xfs: see Documentation/filesystems/xfs.txt
 
 
 Shortcomings
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2d9137e..3be3149 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1730,13 +1730,7 @@  static const struct address_space_operations def_blk_aops = {
  */
 static int blkdev_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
-	return __dax_fault(vma, vmf, blkdev_get_block, NULL);
-}
-
-static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-		pmd_t *pmd, unsigned int flags)
-{
-	return __dax_pmd_fault(vma, addr, pmd, flags, blkdev_get_block, NULL);
+	return dax_fault(vma, vmf, blkdev_get_block, NULL);
 }
 
 static void blkdev_vm_open(struct vm_area_struct *vma)
@@ -1763,7 +1757,7 @@  static const struct vm_operations_struct blkdev_dax_vm_ops = {
 	.open		= blkdev_vm_open,
 	.close		= blkdev_vm_close,
 	.fault		= blkdev_dax_fault,
-	.pmd_fault	= blkdev_dax_pmd_fault,
+	.huge_fault	= blkdev_dax_fault,
 	.pfn_mkwrite	= blkdev_dax_fault,
 };
 
diff --git a/fs/dax.c b/fs/dax.c
index 82d0bff..b82831a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -370,23 +370,7 @@  static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
 	return error;
 }
 
-/**
- * __dax_fault - handle a page fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- * @complete_unwritten: The filesystem method used to convert unwritten blocks
- *	to written so the data written to them is exposed. This is required for
- *	required by write faults for filesystems that will return unwritten
- *	extent mappings from @get_block, but it is optional for reads as
- *	dax_insert_mapping() will always zero unwritten blocks. If the fs does
- *	not support unwritten extents, the it should pass NULL.
- *
- * When a page fault occurs, filesystems may call this helper in their
- * fault handler for DAX files. __dax_fault() assumes the caller has done all
- * the necessary locking for the page fault to proceed successfully.
- */
-int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+static int dax_pte_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 			get_block_t get_block, dax_iodone_t complete_unwritten)
 {
 	struct file *file = vma->vm_file;
@@ -521,34 +505,6 @@  int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	}
 	goto out;
 }
-EXPORT_SYMBOL(__dax_fault);
-
-/**
- * dax_fault - handle a page fault on a DAX file
- * @vma: The virtual memory area where the fault occurred
- * @vmf: The description of the fault
- * @get_block: The filesystem method used to translate file offsets to blocks
- *
- * When a page fault occurs, filesystems may call this helper in their
- * fault handler for DAX files.
- */
-int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
-	      get_block_t get_block, dax_iodone_t complete_unwritten)
-{
-	int result;
-	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
-
-	if (vmf->flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(sb);
-		file_update_time(vma->vm_file);
-	}
-	result = __dax_fault(vma, vmf, get_block, complete_unwritten);
-	if (vmf->flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(sb);
-
-	return result;
-}
-EXPORT_SYMBOL_GPL(dax_fault);
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /*
@@ -565,7 +521,7 @@  static void dax_pmd_dbg(struct block_device *bdev, unsigned long address,
 			? ": " : "", current->comm, address, reason);
 }
 
-int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+static int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 		pmd_t *pmd, unsigned int flags, get_block_t get_block,
 		dax_iodone_t complete_unwritten)
 {
@@ -743,37 +699,46 @@  int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 	result = VM_FAULT_FALLBACK;
 	goto out;
 }
-EXPORT_SYMBOL_GPL(__dax_pmd_fault);
+#else /* !CONFIG_TRANSPARENT_HUGEPAGE */
+static int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+		pmd_t *pmd, unsigned int flags, get_block_t get_block,
+		dax_iodone_t complete_unwritten)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif /* !CONFIG_TRANSPARENT_HUGEPAGE */
 
 /**
- * dax_pmd_fault - handle a PMD fault on a DAX file
+ * dax_fault - handle a page fault on a DAX file
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @get_block: The filesystem method used to translate file offsets to blocks
+ * @iodone: The filesystem method used to convert unwritten blocks
+ *	to written so the data written to them is exposed.  This is required
+ *	by write faults for filesystems that will return unwritten extent
+ *	mappings from @get_block, but it is optional for reads as
+ *	dax_insert_mapping() will always zero unwritten blocks.  If the fs
+ *	does not support unwritten extents, then it should pass NULL.
  *
  * When a page fault occurs, filesystems may call this helper in their
- * pmd_fault handler for DAX files.
+ * fault handler for DAX files.  dax_fault() assumes the caller has done all
+ * the necessary locking for the page fault to proceed successfully.
  */
-int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-			pmd_t *pmd, unsigned int flags, get_block_t get_block,
-			dax_iodone_t complete_unwritten)
+int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+	      get_block_t get_block, dax_iodone_t iodone)
 {
-	int result;
-	struct super_block *sb = file_inode(vma->vm_file)->i_sb;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(sb);
-		file_update_time(vma->vm_file);
+	unsigned long address = (unsigned long)vmf->virtual_address;
+	switch (vmf->flags & FAULT_FLAG_SIZE_MASK) {
+	case FAULT_FLAG_SIZE_PTE:
+		return dax_pte_fault(vma, vmf, get_block, iodone);
+	case FAULT_FLAG_SIZE_PMD:
+		return dax_pmd_fault(vma, address, vmf->pmd, vmf->flags,
+						get_block, iodone);
+	default:
+		return VM_FAULT_FALLBACK;
 	}
-	result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
-				complete_unwritten);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(sb);
-
-	return result;
 }
-EXPORT_SYMBOL_GPL(dax_pmd_fault);
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+EXPORT_SYMBOL_GPL(dax_fault);
 
 /**
  * dax_pfn_mkwrite - handle first write to DAX page
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 11a42c5..ad0a57a 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -51,7 +51,7 @@  static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 	down_read(&ei->dax_sem);
 
-	ret = __dax_fault(vma, vmf, ext2_get_block, NULL);
+	ret = dax_fault(vma, vmf, ext2_get_block, NULL);
 
 	up_read(&ei->dax_sem);
 	if (vmf->flags & FAULT_FLAG_WRITE)
@@ -59,27 +59,6 @@  static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	return ret;
 }
 
-static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	struct inode *inode = file_inode(vma->vm_file);
-	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret;
-
-	if (flags & FAULT_FLAG_WRITE) {
-		sb_start_pagefault(inode->i_sb);
-		file_update_time(vma->vm_file);
-	}
-	down_read(&ei->dax_sem);
-
-	ret = __dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block, NULL);
-
-	up_read(&ei->dax_sem);
-	if (flags & FAULT_FLAG_WRITE)
-		sb_end_pagefault(inode->i_sb);
-	return ret;
-}
-
 static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct inode *inode = file_inode(vma->vm_file);
@@ -90,7 +69,7 @@  static int ext2_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	file_update_time(vma->vm_file);
 	down_read(&ei->dax_sem);
 
-	ret = __dax_mkwrite(vma, vmf, ext2_get_block, NULL);
+	ret = dax_mkwrite(vma, vmf, ext2_get_block, NULL);
 
 	up_read(&ei->dax_sem);
 	sb_end_pagefault(inode->i_sb);
@@ -121,7 +100,7 @@  static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext2_dax_vm_ops = {
 	.fault		= ext2_dax_fault,
-	.pmd_fault	= ext2_dax_pmd_fault,
+	.huge_fault	= ext2_dax_fault,
 	.page_mkwrite	= ext2_dax_mkwrite,
 	.pfn_mkwrite	= ext2_dax_pfn_mkwrite,
 };
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 60683ab..6615499 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -202,54 +202,30 @@  static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 
 	if (write) {
-		sb_start_pagefault(sb);
-		file_update_time(vma->vm_file);
-		down_read(&EXT4_I(inode)->i_mmap_sem);
-		handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
-						EXT4_DATA_TRANS_BLOCKS(sb));
-	} else
-		down_read(&EXT4_I(inode)->i_mmap_sem);
-
-	if (IS_ERR(handle))
-		result = VM_FAULT_SIGBUS;
-	else
-		result = __dax_fault(vma, vmf, ext4_dax_mmap_get_block, NULL);
-
-	if (write) {
-		if (!IS_ERR(handle))
-			ext4_journal_stop(handle);
-		up_read(&EXT4_I(inode)->i_mmap_sem);
-		sb_end_pagefault(sb);
-	} else
-		up_read(&EXT4_I(inode)->i_mmap_sem);
-
-	return result;
-}
-
-static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-						pmd_t *pmd, unsigned int flags)
-{
-	int result;
-	handle_t *handle = NULL;
-	struct inode *inode = file_inode(vma->vm_file);
-	struct super_block *sb = inode->i_sb;
-	bool write = flags & FAULT_FLAG_WRITE;
+		unsigned nblocks;
+		switch (vmf->flags & FAULT_FLAG_SIZE_MASK) {
+		case FAULT_FLAG_SIZE_PTE:
+			nblocks = EXT4_DATA_TRANS_BLOCKS(sb);
+			break;
+		case FAULT_FLAG_SIZE_PMD:
+			nblocks = ext4_chunk_trans_blocks(inode,
+						PMD_SIZE / PAGE_SIZE);
+			break;
+		default:
+			return VM_FAULT_FALLBACK;
+		}
 
-	if (write) {
 		sb_start_pagefault(sb);
 		file_update_time(vma->vm_file);
 		down_read(&EXT4_I(inode)->i_mmap_sem);
-		handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
-				ext4_chunk_trans_blocks(inode,
-							PMD_SIZE / PAGE_SIZE));
+		handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE, nblocks);
 	} else
 		down_read(&EXT4_I(inode)->i_mmap_sem);
 
 	if (IS_ERR(handle))
 		result = VM_FAULT_SIGBUS;
 	else
-		result = __dax_pmd_fault(vma, addr, pmd, flags,
-				ext4_dax_mmap_get_block, NULL);
+		result = dax_fault(vma, vmf, ext4_dax_mmap_get_block, NULL);
 
 	if (write) {
 		if (!IS_ERR(handle))
@@ -270,7 +246,7 @@  static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	sb_start_pagefault(inode->i_sb);
 	file_update_time(vma->vm_file);
 	down_read(&EXT4_I(inode)->i_mmap_sem);
-	err = __dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
+	err = dax_mkwrite(vma, vmf, ext4_dax_mmap_get_block, NULL);
 	up_read(&EXT4_I(inode)->i_mmap_sem);
 	sb_end_pagefault(inode->i_sb);
 
@@ -308,7 +284,7 @@  static int ext4_dax_pfn_mkwrite(struct vm_area_struct *vma,
 
 static const struct vm_operations_struct ext4_dax_vm_ops = {
 	.fault		= ext4_dax_fault,
-	.pmd_fault	= ext4_dax_pmd_fault,
+	.huge_fault	= ext4_dax_fault,
 	.page_mkwrite	= ext4_dax_mkwrite,
 	.pfn_mkwrite	= ext4_dax_pfn_mkwrite,
 };
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index f5392ab..64cde25 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1519,7 +1519,7 @@  xfs_filemap_page_mkwrite(
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
 	if (IS_DAX(inode)) {
-		ret = __dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault, NULL);
+		ret = dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault, NULL);
 	} else {
 		ret = block_page_mkwrite(vma, vmf, xfs_get_blocks);
 		ret = block_page_mkwrite_return(ret);
@@ -1553,7 +1553,7 @@  xfs_filemap_fault(
 		 * changes to xfs_get_blocks_direct() to map unwritten extent
 		 * ioend for conversion on read-only mappings.
 		 */
-		ret = __dax_fault(vma, vmf, xfs_get_blocks_dax_fault, NULL);
+		ret = dax_fault(vma, vmf, xfs_get_blocks_dax_fault, NULL);
 	} else
 		ret = filemap_fault(vma, vmf);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
@@ -1564,16 +1564,14 @@  xfs_filemap_fault(
 /*
  * Similar to xfs_filemap_fault(), the DAX fault path can call into here on
  * both read and write faults. Hence we need to handle both cases. There is no
- * ->pmd_mkwrite callout for huge pages, so we have a single function here to
+ * ->huge_mkwrite callout for huge pages, so we have a single function here to
  * handle both cases here. @flags carries the information on the type of fault
  * occuring.
  */
 STATIC int
-xfs_filemap_pmd_fault(
+xfs_filemap_huge_fault(
 	struct vm_area_struct	*vma,
-	unsigned long		addr,
-	pmd_t			*pmd,
-	unsigned int		flags)
+	struct vm_fault		*vmf)
 {
 	struct inode		*inode = file_inode(vma->vm_file);
 	struct xfs_inode	*ip = XFS_I(inode);
@@ -1582,26 +1580,25 @@  xfs_filemap_pmd_fault(
 	if (!IS_DAX(inode))
 		return VM_FAULT_FALLBACK;
 
-	trace_xfs_filemap_pmd_fault(ip);
+	trace_xfs_filemap_huge_fault(ip);
 
-	if (flags & FAULT_FLAG_WRITE) {
+	if (vmf->flags & FAULT_FLAG_WRITE) {
 		sb_start_pagefault(inode->i_sb);
 		file_update_time(vma->vm_file);
 	}
 
 	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-	ret = __dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault,
-			      NULL);
+	ret = dax_fault(vma, vmf, xfs_get_blocks_dax_fault, NULL);
 	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
-	if (flags & FAULT_FLAG_WRITE)
+	if (vmf->flags & FAULT_FLAG_WRITE)
 		sb_end_pagefault(inode->i_sb);
 
 	return ret;
 }
 
 /*
- * pfn_mkwrite was originally inteneded to ensure we capture time stamp
+ * pfn_mkwrite was originally intended to ensure we capture time stamp
  * updates on write faults. In reality, it's need to serialise against
  * truncate similar to page_mkwrite. Hence we open-code dax_pfn_mkwrite()
  * here and cycle the XFS_MMAPLOCK_SHARED to ensure we serialise the fault
@@ -1636,7 +1633,7 @@  xfs_filemap_pfn_mkwrite(
 
 static const struct vm_operations_struct xfs_file_vm_ops = {
 	.fault		= xfs_filemap_fault,
-	.pmd_fault	= xfs_filemap_pmd_fault,
+	.huge_fault	= xfs_filemap_huge_fault,
 	.map_pages	= filemap_map_pages,
 	.page_mkwrite	= xfs_filemap_page_mkwrite,
 	.pfn_mkwrite	= xfs_filemap_pfn_mkwrite,
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 877079eb..8f810db 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -687,7 +687,7 @@  DEFINE_INODE_EVENT(xfs_inode_clear_eofblocks_tag);
 DEFINE_INODE_EVENT(xfs_inode_free_eofblocks_invalid);
 
 DEFINE_INODE_EVENT(xfs_filemap_fault);
-DEFINE_INODE_EVENT(xfs_filemap_pmd_fault);
+DEFINE_INODE_EVENT(xfs_filemap_huge_fault);
 DEFINE_INODE_EVENT(xfs_filemap_page_mkwrite);
 DEFINE_INODE_EVENT(xfs_filemap_pfn_mkwrite);
 
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b415e52..f2f1cc2 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -12,25 +12,8 @@  int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
 int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,
 		dax_iodone_t);
-int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,
-		dax_iodone_t);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t, dax_iodone_t);
-int __dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-				unsigned int flags, get_block_t, dax_iodone_t);
-#else
-static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-				pmd_t *pmd, unsigned int flags, get_block_t gb,
-				dax_iodone_t di)
-{
-	return VM_FAULT_FALLBACK;
-}
-#define __dax_pmd_fault dax_pmd_fault
-#endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
 #define dax_mkwrite(vma, vmf, gb, iod)		dax_fault(vma, vmf, gb, iod)
-#define __dax_mkwrite(vma, vmf, gb, iod)	__dax_fault(vma, vmf, gb, iod)
 
 static inline bool vma_is_dax(struct vm_area_struct *vma)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4bf3811..099e641 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -233,15 +233,21 @@  extern pgprot_t protection_map[16];
 #define FAULT_FLAG_TRIED	0x20	/* Second try */
 #define FAULT_FLAG_USER		0x40	/* The fault originated in userspace */
 
+#define FAULT_FLAG_SIZE_MASK	0x700	/* Support up to 8-level page tables */
+#define FAULT_FLAG_SIZE_PTE	0x000	/* First level (eg 4k) */
+#define FAULT_FLAG_SIZE_PMD	0x100	/* Second level (eg 2MB) */
+#define FAULT_FLAG_SIZE_PUD	0x200	/* Third level (eg 1GB) */
+#define FAULT_FLAG_SIZE_PGD	0x300	/* Fourth level (eg 512GB) */
+
 /*
- * vm_fault is filled by the the pagefault handler and passed to the vma's
+ * vm_fault is filled in by the pagefault handler and passed to the vma's
  * ->fault function. The vma's ->fault is responsible for returning a bitmask
  * of VM_FAULT_xxx flags that give details about how the fault was handled.
  *
  * MM layer fills up gfp_mask for page allocations but fault handler might
  * alter it if its implementation requires a different allocation context.
  *
- * pgoff should be used in favour of virtual_address, if possible.
+ * pgoff should be used instead of virtual_address, if possible.
  */
 struct vm_fault {
 	unsigned int flags;		/* FAULT_FLAG_xxx flags */
@@ -258,7 +264,12 @@  struct vm_fault {
 	/* for ->map_pages() only */
 	pgoff_t max_pgoff;		/* map pages for offset from pgoff till
 					 * max_pgoff inclusive */
-	pte_t *pte;			/* pte entry associated with ->pgoff */
+	union {
+		pte_t *pte;		/* pte entry associated with ->pgoff */
+		pmd_t *pmd;
+		pud_t *pud;
+		pgd_t *pgd;
+	};
 };
 
 /*
@@ -271,8 +282,7 @@  struct vm_operations_struct {
 	void (*close)(struct vm_area_struct * area);
 	int (*mremap)(struct vm_area_struct * area);
 	int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
-	int (*pmd_fault)(struct vm_area_struct *, unsigned long address,
-						pmd_t *, unsigned int flags);
+	int (*huge_fault)(struct vm_area_struct *, struct vm_fault *vmf);
 	void (*map_pages)(struct vm_area_struct *vma, struct vm_fault *vmf);
 
 	/* notification that a previously read-only page is about to become
diff --git a/mm/memory.c b/mm/memory.c
index 8c6392c..f5d7e9a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3238,10 +3238,16 @@  out:
 static int create_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pmd_t *pmd, unsigned int flags)
 {
+	struct vm_fault vmf = {
+		.virtual_address = (void __user *)address,
+		.flags = flags | FAULT_FLAG_SIZE_PMD,
+		.pmd = pmd,
+	};
+
 	if (vma_is_anonymous(vma))
 		return do_huge_pmd_anonymous_page(mm, vma, address, pmd, flags);
-	if (vma->vm_ops->pmd_fault)
-		return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
+	if (vma->vm_ops->huge_fault)
+		return vma->vm_ops->huge_fault(vma, &vmf);
 	return VM_FAULT_FALLBACK;
 }
 
@@ -3249,10 +3255,16 @@  static int wp_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pmd_t *pmd, pmd_t orig_pmd,
 			unsigned int flags)
 {
+	struct vm_fault vmf = {
+		.virtual_address = (void __user *)address,
+		.flags = flags | FAULT_FLAG_SIZE_PMD,
+		.pmd = pmd,
+	};
+
 	if (vma_is_anonymous(vma))
 		return do_huge_pmd_wp_page(mm, vma, address, pmd, orig_pmd);
-	if (vma->vm_ops->pmd_fault)
-		return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
+	if (vma->vm_ops->huge_fault)
+		return vma->vm_ops->huge_fault(vma, &vmf);
 	return VM_FAULT_FALLBACK;
 }