[PATCH v5 1/1] f2fs: dax: implement direct access

[sunqiuyang <sunqiuyang@xxxxxxxxxx>]

From: Qiuyang Sun <sunqiuyang@xxxxxxxxxx>

This patch implements Direct Access (DAX) in F2FS, including:
- a mount option to choose whether to enable DAX or not
- read/write and mmap of regular files in the DAX way
- zero-out of unaligned partial blocks in the DAX way
- garbage collection of DAX files, by mapping both old and new physical
  addresses of a data page into memory and copy data between them directly
- incompatibility of DAX with inline data, atomic or volatile write, etc.

Signed-off-by: Qiuyang Sun <sunqiuyang@xxxxxxxxxx>
---
Changlog v4 -> v5:

In DAX write, to avoid stale data, the newly allocated blocks should be
zeroed out before writing to them. We introduce a new flag
F2FS_GET_BLOCK_ZERO for f2fs_map_blocks(), for which a single struct
f2fs_map_blocks can never contain old and new blocks at the same time, so
that zeroing out new blocks would not affect old ones. This flag is used in
the write path of f2fs_iomap_begin() for DAX I/O, replacing 
F2FS_GET_BLOCK_PRE_DIO in earlier versions.

---
 fs/f2fs/data.c   | 115 +++++++++++++++++++++++++++++++++
 fs/f2fs/f2fs.h   |   9 +++
 fs/f2fs/file.c   | 192 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 fs/f2fs/gc.c     | 104 ++++++++++++++++++++++++++++--
 fs/f2fs/inline.c |   4 ++
 fs/f2fs/inode.c  |   8 ++-
 fs/f2fs/namei.c  |   5 ++
 fs/f2fs/super.c  |  15 +++++
 8 files changed, 445 insertions(+), 7 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 7d3af48..b28d97a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -908,6 +908,15 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 				err = -EIO;
 				goto sync_out;
 			}
+			/*
+			 * If newly allocated blocks are to be zeroed out later,
+			 * a single f2fs_map_blocks must not contain both old
+			 * and new blocks at the same time.
+			 */
+			if (flag == F2FS_GET_BLOCK_ZERO
+					&& (map->m_flags & F2FS_MAP_MAPPED)
+					&& !(map->m_flags & F2FS_MAP_NEW))
+				goto sync_out;
 			if (flag == F2FS_GET_BLOCK_PRE_AIO) {
 				if (blkaddr == NULL_ADDR) {
 					prealloc++;
@@ -994,6 +1003,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 	goto next_dnode;
 
 sync_out:
+	if (flag == F2FS_GET_BLOCK_ZERO && map->m_flags & F2FS_MAP_NEW) {
+		clean_bdev_aliases(inode->i_sb->s_bdev,
+				map->m_pblk, map->m_len);
+		sb_issue_zeroout(inode->i_sb, map->m_pblk,
+				map->m_len, GFP_NOFS);
+	}
 	f2fs_put_dnode(&dn);
 unlock_out:
 	if (create) {
@@ -2257,3 +2272,103 @@ int f2fs_migrate_page(struct address_space *mapping,
 	.migratepage    = f2fs_migrate_page,
 #endif
 };
+
+#ifdef CONFIG_FS_DAX
+#include <linux/iomap.h>
+#include <linux/dax.h>
+
+static int f2fs_iomap_begin(struct inode *inode, loff_t offset,
+	loff_t length, unsigned int flags, struct iomap *iomap)
+{
+	struct block_device *bdev;
+	unsigned long first_block = F2FS_BYTES_TO_BLK(offset);
+	unsigned long last_block = F2FS_BYTES_TO_BLK(offset + length - 1);
+	struct f2fs_map_blocks map;
+	int ret;
+
+	if (WARN_ON_ONCE(f2fs_has_inline_data(inode)))
+		return -ERANGE;
+
+	map.m_lblk = first_block;
+	map.m_len = last_block - first_block + 1;
+	map.m_next_pgofs = NULL;
+
+	if (!(flags & IOMAP_WRITE))
+		ret = f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_FIEMAP);
+	else {
+	/* i_size should be kept here and changed later in f2fs_iomap_end */
+		loff_t original_i_size = i_size_read(inode);
+
+		ret = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_ZERO);
+		if (i_size_read(inode) > original_i_size) {
+			f2fs_i_size_write(inode, original_i_size);
+			if (ret) {
+				truncate_pagecache(inode, original_i_size);
+				truncate_blocks(inode, original_i_size, true);
+			}
+		}
+	}
+
+	if (ret)
+		return ret;
+
+	iomap->flags = 0;
+	bdev = inode->i_sb->s_bdev;
+	iomap->bdev = bdev;
+	if (blk_queue_dax(bdev->bd_queue))
+		iomap->dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+	else
+		iomap->dax_dev = NULL;
+	iomap->offset = F2FS_BLK_TO_BYTES((u64)first_block);
+
+	if (map.m_len == 0) {
+		iomap->type = IOMAP_HOLE;
+		iomap->blkno = IOMAP_NULL_BLOCK;
+		iomap->length = F2FS_BLKSIZE;
+	} else {
+		if (map.m_flags & F2FS_MAP_UNWRITTEN)
+			iomap->type = IOMAP_UNWRITTEN;
+		else if (map.m_flags & F2FS_MAP_MAPPED)
+			iomap->type = IOMAP_MAPPED;
+		else {
+			WARN_ON_ONCE(1);
+			return -EIO;
+		}
+		iomap->blkno =
+			(sector_t)map.m_pblk << F2FS_LOG_SECTORS_PER_BLOCK;
+		iomap->length = F2FS_BLK_TO_BYTES((u64)map.m_len);
+	}
+
+	if (map.m_flags & F2FS_MAP_NEW)
+		iomap->flags |= IOMAP_F_NEW;
+	return 0;
+}
+
+static int f2fs_iomap_end(struct inode *inode, loff_t offset, loff_t length,
+	ssize_t written, unsigned int flags, struct iomap *iomap)
+{
+	put_dax(iomap->dax_dev);
+	if (!(flags & IOMAP_WRITE) || (flags & IOMAP_FAULT))
+		return 0;
+
+	if (offset + written > i_size_read(inode))
+		f2fs_i_size_write(inode, offset + written);
+
+	if (iomap->offset + iomap->length >
+			ALIGN(i_size_read(inode), F2FS_BLKSIZE)) {
+		block_t written_blk = F2FS_BYTES_TO_BLK(offset + written);
+		block_t end_blk = F2FS_BYTES_TO_BLK(offset + length);
+
+		if (written_blk < end_blk)
+			f2fs_write_failed(inode->i_mapping, offset + length);
+	}
+
+	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
+	return 0;
+}
+
+struct iomap_ops f2fs_iomap_ops = {
+	.iomap_begin	= f2fs_iomap_begin,
+	.iomap_end	= f2fs_iomap_end,
+};
+#endif
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index db5d7ae..f79d904 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -88,6 +88,11 @@ struct f2fs_fault_info {
 #define F2FS_MOUNT_FAULT_INJECTION	0x00010000
 #define F2FS_MOUNT_ADAPTIVE		0x00020000
 #define F2FS_MOUNT_LFS			0x00040000
+#ifdef CONFIG_FS_DAX
+#define F2FS_MOUNT_DAX			0x00080000 /* Direct Access */
+#else
+#define F2FS_MOUNT_DAX			0
+#endif
 
 #define clear_opt(sbi, option)	((sbi)->mount_opt.opt &= ~F2FS_MOUNT_##option)
 #define set_opt(sbi, option)	((sbi)->mount_opt.opt |= F2FS_MOUNT_##option)
@@ -476,6 +481,7 @@ struct f2fs_map_blocks {
 #define F2FS_GET_BLOCK_BMAP		3
 #define F2FS_GET_BLOCK_PRE_DIO		4
 #define F2FS_GET_BLOCK_PRE_AIO		5
+#define F2FS_GET_BLOCK_ZERO		6
 
 /*
  * i_advise uses FADVISE_XXX_BIT. We can add additional hints later.
@@ -2402,6 +2408,9 @@ void f2fs_invalidate_page(struct page *page, unsigned int offset,
 int f2fs_migrate_page(struct address_space *mapping, struct page *newpage,
 			struct page *page, enum migrate_mode mode);
 #endif
+#ifdef CONFIG_FS_DAX
+extern struct iomap_ops f2fs_iomap_ops;
+#endif
 
 /*
  * gc.c
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 3f56b27..73aca18 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -23,6 +23,10 @@
 #include <linux/uio.h>
 #include <linux/uuid.h>
 #include <linux/file.h>
+#ifdef CONFIG_FS_DAX
+#include <linux/dax.h>
+#include <linux/iomap.h>
+#endif
 
 #include "f2fs.h"
 #include "node.h"
@@ -121,6 +125,64 @@ static int f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	.page_mkwrite	= f2fs_vm_page_mkwrite,
 };
 
+#ifdef CONFIG_FS_DAX
+static int f2fs_dax_huge_fault(struct vm_fault *vmf,
+	enum page_entry_size pe_size)
+{
+	int result;
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct super_block *sb = inode->i_sb;
+	bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+	if (write) {
+		sb_start_pagefault(sb);
+		file_update_time(vmf->vma->vm_file);
+	}
+	down_read(&F2FS_I(inode)->i_mmap_sem);
+	result = dax_iomap_fault(vmf, pe_size, &f2fs_iomap_ops);
+	up_read(&F2FS_I(inode)->i_mmap_sem);
+	if (write)
+		sb_end_pagefault(sb);
+
+	return result;
+}
+
+static int f2fs_dax_fault(struct vm_fault *vmf)
+{
+	return f2fs_dax_huge_fault(vmf, PE_SIZE_PTE);
+}
+
+static int f2fs_dax_pfn_mkwrite(struct vm_fault *vmf)
+{
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct super_block *sb = inode->i_sb;
+	loff_t size;
+	int ret;
+
+	sb_start_pagefault(sb);
+	file_update_time(vmf->vma->vm_file);
+	down_read(&F2FS_I(inode)->i_mmap_sem);
+	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (vmf->pgoff >= size)
+		ret = VM_FAULT_SIGBUS;
+	else
+		ret = dax_pfn_mkwrite(vmf);
+	up_read(&F2FS_I(inode)->i_mmap_sem);
+	sb_end_pagefault(sb);
+
+	return ret;
+}
+
+static const struct vm_operations_struct f2fs_dax_vm_ops = {
+	.fault		= f2fs_dax_fault,
+	.huge_fault	= f2fs_dax_huge_fault,
+	.page_mkwrite	= f2fs_dax_fault,
+	.pfn_mkwrite	= f2fs_dax_pfn_mkwrite,
+};
+#else
+#define f2fs_dax_vm_ops f2fs_file_vm_ops
+#endif
+
 static int get_parent_ino(struct inode *inode, nid_t *pino)
 {
 	struct dentry *dentry;
@@ -436,7 +498,13 @@ static int f2fs_file_mmap(struct file *file, struct vm_area_struct *vma)
 		return err;
 
 	file_accessed(file);
-	vma->vm_ops = &f2fs_file_vm_ops;
+
+	if (IS_DAX(inode)) {
+		vma->vm_ops = &f2fs_dax_vm_ops;
+		vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	} else
+		vma->vm_ops = &f2fs_file_vm_ops;
+
 	return 0;
 }
 
@@ -520,6 +588,17 @@ static int truncate_partial_data_page(struct inode *inode, u64 from,
 	if (!offset && !cache_only)
 		return 0;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode)) {
+		int ret;
+
+		down_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+		ret = iomap_zero_range(inode, from, PAGE_SIZE - offset,
+			NULL, &f2fs_iomap_ops);
+		up_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+		return ret;
+	}
+#endif
 	if (cache_only) {
 		page = find_lock_page(mapping, index);
 		if (page && PageUptodate(page))
@@ -786,6 +865,18 @@ static int fill_zero(struct inode *inode, pgoff_t index,
 	if (!len)
 		return 0;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode)) {
+		int ret;
+
+		down_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+		ret = iomap_zero_range(inode,
+			F2FS_BLK_TO_BYTES((loff_t)index) + start,
+			len, NULL, &f2fs_iomap_ops);
+		up_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+		return ret;
+	}
+#endif
 	f2fs_balance_fs(sbi, true);
 
 	f2fs_lock_op(sbi);
@@ -1108,6 +1199,11 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 	loff_t new_size;
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	/* The current implementation does not apply to DAX files. */
+	if (IS_DAX(inode))
+		return -EINVAL;
+#endif
 	if (offset + len >= i_size_read(inode))
 		return -EINVAL;
 
@@ -1298,6 +1394,11 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
 	loff_t new_size;
 	int ret = 0;
 
+#ifdef CONFIG_FS_DAX
+	/* The current implementation does not apply to DAX files. */
+	if (IS_DAX(inode))
+		return -EINVAL;
+#endif
 	new_size = i_size_read(inode) + len;
 	ret = inode_newsize_ok(inode, new_size);
 	if (ret)
@@ -1561,6 +1662,10 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode))
+		return -EINVAL;
+#endif
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
@@ -1610,6 +1715,9 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	f2fs_bug_on(F2FS_I_SB(inode), IS_DAX(inode));
+#endif
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
@@ -1646,6 +1754,10 @@ static int f2fs_ioc_start_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode))
+		return -EINVAL;
+#endif
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
@@ -1681,6 +1793,9 @@ static int f2fs_ioc_release_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	f2fs_bug_on(F2FS_I_SB(inode), IS_DAX(inode));
+#endif
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
@@ -1710,6 +1825,9 @@ static int f2fs_ioc_abort_volatile_write(struct file *filp)
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	f2fs_bug_on(F2FS_I_SB(inode), IS_DAX(inode));
+#endif
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
@@ -2124,6 +2242,10 @@ static int f2fs_ioc_defragment(struct file *filp, unsigned long arg)
 	struct f2fs_defragment range;
 	int err;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode))
+		return -EINVAL;
+#endif
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
@@ -2173,6 +2295,10 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
 	size_t dst_osize;
 	int ret;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(src) || IS_DAX(dst))
+		return -EINVAL;
+#endif
 	if (file_in->f_path.mnt != file_out->f_path.mnt ||
 				src->i_sb != dst->i_sb)
 		return -EXDEV;
@@ -2414,6 +2540,61 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	}
 }
 
+#ifdef CONFIG_FS_DAX
+static ssize_t f2fs_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	inode_lock_shared(inode);
+
+	if (!IS_DAX(inode)) {
+		inode_unlock_shared(inode);
+		return generic_file_read_iter(iocb, to);
+	}
+
+	down_read(&F2FS_I(inode)->dio_rwsem[READ]);
+	ret = dax_iomap_rw(iocb, to, &f2fs_iomap_ops);
+	up_read(&F2FS_I(inode)->dio_rwsem[READ]);
+	inode_unlock_shared(inode);
+
+	file_accessed(iocb->ki_filp);
+	return ret;
+}
+
+static ssize_t f2fs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	if (!iov_iter_count(to))
+		return 0; /* skip atime */
+
+	if (IS_DAX(file_inode(iocb->ki_filp)))
+		return f2fs_dax_read_iter(iocb, to);
+
+	return generic_file_read_iter(iocb, to);
+}
+
+static ssize_t f2fs_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	ret = file_remove_privs(iocb->ki_filp);
+	if (ret)
+		return ret;
+	ret = file_update_time(iocb->ki_filp);
+	if (ret)
+		return ret;
+
+	down_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+	ret = dax_iomap_rw(iocb, from, &f2fs_iomap_ops);
+	up_read(&F2FS_I(inode)->dio_rwsem[WRITE]);
+
+	return ret;
+}
+#else
+#define f2fs_dax_write_iter	__generic_file_write_iter
+#endif
+
 static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
@@ -2435,7 +2616,10 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			return err;
 		}
 		blk_start_plug(&plug);
-		ret = __generic_file_write_iter(iocb, from);
+		if (IS_DAX(inode))
+			ret = f2fs_dax_write_iter(iocb, from);
+		else
+			ret = __generic_file_write_iter(iocb, from);
 		blk_finish_plug(&plug);
 		clear_inode_flag(inode, FI_NO_PREALLOC);
 	}
@@ -2484,7 +2668,11 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 const struct file_operations f2fs_file_operations = {
 	.llseek		= f2fs_llseek,
+#ifdef CONFIG_FS_DAX
+	.read_iter	= f2fs_file_read_iter,
+#else
 	.read_iter	= generic_file_read_iter,
+#endif
 	.write_iter	= f2fs_file_write_iter,
 	.open		= f2fs_file_open,
 	.release	= f2fs_release_file,
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index fa3d2e2..ade4f71 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -700,6 +700,100 @@ static void move_encrypted_block(struct inode *inode, block_t bidx,
 	f2fs_put_page(page, 1);
 }
 
+#ifdef CONFIG_FS_DAX
+#include <linux/dax.h>
+
+static void dax_move_data_page(struct inode *inode, block_t bidx,
+				unsigned int segno, int off)
+{
+	struct block_device *bdev = inode->i_sb->s_bdev;
+	struct dax_device *dax_dev;
+	struct dnode_of_data dn;
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct f2fs_summary sum;
+	struct node_info ni;
+	block_t old_blkaddr, new_blkaddr;
+	int err, id;
+	long map_len;
+	pgoff_t pgoff;
+	void *kaddr_old, *kaddr_new;
+	pfn_t pfn;
+
+	f2fs_bug_on(sbi, f2fs_is_atomic_file(inode));
+
+	if (blk_queue_dax(bdev->bd_queue))
+		dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+	else
+		return;
+
+	if (!check_valid_map(sbi, segno, off))
+		return;
+
+	if (!down_write_trylock(&F2FS_I(inode)->i_mmap_sem))
+		return;
+
+	unmap_mapping_range(inode->i_mapping, (loff_t)bidx << PAGE_SHIFT,
+			PAGE_SIZE, 1);
+	/* find the old block address */
+	set_new_dnode(&dn, inode, NULL, NULL, 0);
+	err = get_dnode_of_data(&dn, bidx, LOOKUP_NODE);
+	if (err)
+		goto out;
+	old_blkaddr = dn.data_blkaddr;
+	/* This page is already truncated */
+	if (old_blkaddr == NULL_ADDR)
+		goto put_dn;
+
+	/* allocate a new block address */
+	get_node_info(sbi, dn.nid, &ni);
+	set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);
+	allocate_data_block(sbi, NULL, old_blkaddr, &new_blkaddr,
+			&sum, CURSEG_COLD_DATA, NULL, false);
+
+	/* copy data page from old to new address in dax_bdev */
+	id = dax_read_lock();
+	err = bdev_dax_pgoff(bdev, SECTOR_FROM_BLOCK(old_blkaddr),
+			PAGE_SIZE, &pgoff);
+	if (err)
+		goto recover;
+	map_len = dax_direct_access(dax_dev, pgoff, 1, &kaddr_old, &pfn);
+	if (map_len < 0)
+		goto recover;
+	err = bdev_dax_pgoff(bdev, SECTOR_FROM_BLOCK(new_blkaddr),
+			PAGE_SIZE, &pgoff);
+	if (err)
+		goto recover;
+	map_len = dax_direct_access(dax_dev, pgoff, 1, &kaddr_new, &pfn);
+	if (map_len < 0)
+		goto recover;
+	copy_page((void __force *)kaddr_new, (void __force *)kaddr_old);
+
+	f2fs_update_data_blkaddr(&dn, new_blkaddr);
+	set_inode_flag(inode, FI_APPEND_WRITE);
+	if (bidx == 0)
+		set_inode_flag(inode, FI_FIRST_BLOCK_WRITTEN);
+
+recover:
+	if (err || map_len < 0)
+		__f2fs_replace_block(sbi, &sum, new_blkaddr, old_blkaddr,
+							true, true);
+	dax_read_unlock(id);
+put_dn:
+	f2fs_put_dnode(&dn);
+out:
+	unmap_mapping_range(inode->i_mapping, (loff_t)bidx << PAGE_SHIFT,
+			PAGE_SIZE, 1);
+	up_write(&F2FS_I(inode)->i_mmap_sem);
+	put_dax(dax_dev);
+}
+#else
+static void dax_move_data_page(struct inode *inode, block_t bidx,
+				unsigned int segno, int off)
+{
+	return;
+}
+#endif
+
 static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
 							unsigned int segno, int off)
 {
@@ -818,9 +912,9 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 			if (IS_ERR(inode) || is_bad_inode(inode))
 				continue;
 
-			/* if encrypted inode, let's go phase 3 */
-			if (f2fs_encrypted_inode(inode) &&
-						S_ISREG(inode->i_mode)) {
+			/* if DAX or encrypted inode, let's go phase 3 */
+			if (IS_DAX(inode) || (f2fs_encrypted_inode(inode) &&
+						S_ISREG(inode->i_mode))) {
 				add_gc_inode(gc_list, inode);
 				continue;
 			}
@@ -858,7 +952,9 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 
 			start_bidx = start_bidx_of_node(nofs, inode)
 								+ ofs_in_node;
-			if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
+			if (IS_DAX(inode))
+				dax_move_data_page(inode, start_bidx, segno, off);
+			else if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
 				move_encrypted_block(inode, start_bidx, segno, off);
 			else
 				move_data_page(inode, start_bidx, gc_type, segno, off);
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index e0fd437..fd8b290 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -28,6 +28,10 @@ bool f2fs_may_inline_data(struct inode *inode)
 	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
 		return false;
 
+#ifdef CONFIG_FS_DAX
+	if (IS_DAX(inode))
+		return false;
+#endif
 	return true;
 }
 
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 1ff5bd4..aa16c52 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -43,8 +43,14 @@ void f2fs_set_inode_flags(struct inode *inode)
 		new_fl |= S_NOATIME;
 	if (flags & FS_DIRSYNC_FL)
 		new_fl |= S_DIRSYNC;
+#ifdef CONFIG_FS_DAX
+	if (test_opt(F2FS_I_SB(inode), DAX) && S_ISREG(inode->i_mode) &&
+		!f2fs_has_inline_data(inode) && !f2fs_encrypted_inode(inode) &&
+		!f2fs_is_atomic_file(inode) && !f2fs_is_volatile_file(inode))
+		new_fl |= S_DAX;
+#endif
 	inode_set_flags(inode, new_fl,
-			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
+			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);
 }
 
 static void __get_inode_rdev(struct inode *inode, struct f2fs_inode *ri)
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index c31b40e..8feeb9a 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -60,6 +60,11 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
 	if (f2fs_encrypted_inode(dir) && f2fs_may_encrypt(inode))
 		f2fs_set_encrypted_inode(inode);
 
+#ifdef CONFIG_FS_DAX
+	if (test_opt(sbi, DAX) && S_ISREG(inode->i_mode) &&
+		!f2fs_has_inline_data(inode) && !f2fs_encrypted_inode(inode))
+		inode->i_flags |= S_DAX;
+#endif
 	set_inode_flag(inode, FI_NEW_INODE);
 
 	if (test_opt(sbi, INLINE_XATTR))
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 8e39b85..74277cd 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -106,6 +106,7 @@ enum {
 	Opt_fault_injection,
 	Opt_lazytime,
 	Opt_nolazytime,
+	Opt_dax,
 	Opt_err,
 };
 
@@ -141,6 +142,7 @@ enum {
 	{Opt_fault_injection, "fault_injection=%u"},
 	{Opt_lazytime, "lazytime"},
 	{Opt_nolazytime, "nolazytime"},
+	{Opt_dax, "dax"},
 	{Opt_err, NULL},
 };
 
@@ -380,6 +382,15 @@ static int parse_options(struct super_block *sb, char *options)
 		case Opt_nolazytime:
 			sb->s_flags &= ~MS_LAZYTIME;
 			break;
+#ifdef CONFIG_FS_DAX
+		case Opt_dax:
+			set_opt(sbi, DAX);
+			break;
+#else
+		case Opt_dax:
+			f2fs_msg(sb, KERN_INFO, "dax option not supported");
+			break;
+#endif
 		default:
 			f2fs_msg(sb, KERN_ERR,
 				"Unrecognized mount option \"%s\" or missing value",
@@ -775,6 +786,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 		seq_printf(seq, ",fault_injection=%u",
 				sbi->fault_info.inject_rate);
 #endif
+#ifdef CONFIG_FS_DAX
+	if (test_opt(sbi, DAX))
+		seq_puts(seq, ",dax");
+#endif
 
 	return 0;
 }
-- 
1.8.3.1