This patch implements Direct Access (DAX) in F2FS, including:
 - a mount option to enable DAX
 - read/write and mmap of regular files in the DAX way
 - zero-out of non-aligned partial blocks in the DAX way
 - garbage collection of DAX files
 - incompatibility of DAX with inline data, atomic or volatile write

TODO: We may need new implementation of f2fs_collapse/insert_range() for 
DAX files, as filemap_write_and_wait_range() does not work for DAX files, 
and thus the data pages cannot be moved correctly.

Signed-off-by: Qiuyang Sun <sunqiuy...@huawei.com>
---
 fs/f2fs/f2fs.h   |   8 +++
 fs/f2fs/file.c   | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 fs/f2fs/gc.c     |  69 +++++++++++++++++--
 fs/f2fs/inline.c |   4 ++
 fs/f2fs/inode.c  |  88 +++++++++++++++++++++++++
 fs/f2fs/namei.c  |   7 ++
 fs/f2fs/super.c  |  16 +++++
 7 files changed, 383 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index f7957ca..d0e8af5 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -87,6 +87,11 @@ 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)
@@ -2063,6 +2068,9 @@ int f2fs_getattr(const struct path *path, struct kstat 
*stat,
 int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc);
 void f2fs_evict_inode(struct inode *inode);
 void handle_failed_inode(struct inode *inode);
+#ifdef CONFIG_FS_DAX
+extern struct iomap_ops f2fs_iomap_ops;
+#endif
 
 /*
  * namei.c
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 165acbf..4eeb17b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -23,6 +23,8 @@
 #include <linux/uio.h>
 #include <linux/uuid.h>
 #include <linux/file.h>
+#include <linux/dax.h>
+#include <linux/iomap.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -106,6 +108,64 @@ 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;
@@ -434,7 +494,13 @@ 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(file_inode(file))) {
+               vma->vm_ops = &f2fs_dax_vm_ops;
+               vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+       } else {
+               vma->vm_ops = &f2fs_file_vm_ops;
+       }
+
        return 0;
 }
 
@@ -518,6 +584,18 @@ 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))
@@ -750,6 +828,19 @@ 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);
@@ -1073,6 +1164,12 @@ 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 original implementation does not apply to DAX files. */
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        if (offset + len >= i_size_read(inode))
                return -EINVAL;
 
@@ -1265,6 +1362,12 @@ 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 original implementation does not apply to DAX files. */
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        new_size = i_size_read(inode) + len;
        if (new_size > inode->i_sb->s_maxbytes)
                return -EFBIG;
@@ -1527,6 +1630,11 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+#ifdef CONFIG_FS_DAX
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        ret = mnt_want_write_file(filp);
        if (ret)
                return ret;
@@ -1568,6 +1676,11 @@ static int f2fs_ioc_commit_atomic_write(struct file 
*filp)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+#ifdef CONFIG_FS_DAX
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        ret = mnt_want_write_file(filp);
        if (ret)
                return ret;
@@ -1604,6 +1717,11 @@ static int f2fs_ioc_start_volatile_write(struct file 
*filp)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+#ifdef CONFIG_FS_DAX
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        ret = mnt_want_write_file(filp);
        if (ret)
                return ret;
@@ -1633,6 +1751,11 @@ static int f2fs_ioc_release_volatile_write(struct file 
*filp)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+#ifdef CONFIG_FS_DAX
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        ret = mnt_want_write_file(filp);
        if (ret)
                return ret;
@@ -1662,6 +1785,11 @@ static int f2fs_ioc_abort_volatile_write(struct file 
*filp)
        if (!inode_owner_or_capable(inode))
                return -EACCES;
 
+#ifdef CONFIG_FS_DAX
+       if (IS_DAX(inode))
+               return -EINVAL;
+#endif
+
        ret = mnt_want_write_file(filp);
        if (ret)
                return ret;
@@ -2252,6 +2380,64 @@ 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
+static ssize_t f2fs_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+       return __generic_file_write_iter(iocb, from);
+}
+#endif
+
 static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
        struct file *file = iocb->ki_filp;
@@ -2278,7 +2464,10 @@ 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);
        }
@@ -2326,7 +2515,11 @@ 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 418fd98..70cbd39 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -16,6 +16,7 @@
 #include <linux/kthread.h>
 #include <linux/delay.h>
 #include <linux/freezer.h>
+#include <linux/dax.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -671,6 +672,64 @@ static void move_encrypted_block(struct inode *inode, 
block_t bidx,
        f2fs_put_page(page, 1);
 }
 
+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 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;
+       struct blk_dax_ctl old_dax, new_dax;
+       int err;
+
+       if (!check_valid_map(sbi, segno, off))
+               return;
+
+       if (f2fs_is_atomic_file(inode))
+               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 || dn.data_blkaddr == NULL_ADDR)
+               return;
+       old_blkaddr = dn.data_blkaddr;
+
+       /* allocate a new block address */
+       get_node_info(sbi, dn.nid, &ni);
+       set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);
+       mutex_lock(&sbi->wio_mutex[DATA]);
+       allocate_data_block(sbi, NULL, old_blkaddr,
+                       &new_blkaddr, &sum, CURSEG_COLD_DATA);
+       /* copy data page within directly accessed bdev */
+       old_dax.sector = SECTOR_FROM_BLOCK(old_blkaddr);
+       new_dax.sector = SECTOR_FROM_BLOCK(new_blkaddr);
+       old_dax.size = new_dax.size = PAGE_SIZE;
+       dax_map_atomic(bdev, &old_dax);
+       dax_map_atomic(bdev, &new_dax);
+       copy_page((void __force *)new_dax.addr, (void __force *)old_dax.addr);
+       dax_unmap_atomic(bdev, &new_dax);
+       dax_unmap_atomic(bdev, &old_dax);
+       mutex_unlock(&sbi->wio_mutex[DATA]);
+
+       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);
+       f2fs_put_dnode(&dn);
+
+       unmap_mapping_range(inode->i_mapping,
+               (loff_t)bidx << PAGE_SHIFT, PAGE_SIZE, 1);
+       up_write(&F2FS_I(inode)->i_mmap_sem);
+}
+
 static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
                                                        unsigned int segno, int 
off)
 {
@@ -786,9 +845,9 @@ 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;
                        }
@@ -826,7 +885,9 @@ 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 e32a9e5..4b9d853 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 24bb821..96e1f57 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -13,6 +13,7 @@
 #include <linux/buffer_head.h>
 #include <linux/backing-dev.h>
 #include <linux/writeback.h>
+#include <linux/iomap.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -478,3 +479,90 @@ void handle_failed_inode(struct inode *inode)
        /* iput will drop the inode object */
        iput(inode);
 }
+
+#ifdef CONFIG_FS_DAX
+static int f2fs_iomap_begin(struct inode *inode, loff_t offset,
+       loff_t length, unsigned int flags, struct iomap *iomap)
+{
+       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;
+       loff_t original_i_size = i_size_read(inode);
+
+       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_READ);
+       else {
+               ret = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);
+       /* i_size should be kept here and changed later in f2fs_iomap_end */
+               if (i_size_read(inode) != original_i_size)
+                       f2fs_i_size_write(inode, original_i_size);
+       }
+
+       if (ret)
+               return ret;
+
+       iomap->flags = 0;
+       iomap->bdev = inode->i_sb->s_bdev;
+       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_MAPPED) {
+                       iomap->type = IOMAP_MAPPED;
+               } else if (map.m_flags & F2FS_MAP_UNWRITTEN) {
+                       iomap->type = IOMAP_UNWRITTEN;
+               } 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)
+{
+       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(inode->i_size, 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) {
+                       down_write(&F2FS_I(inode)->i_mmap_sem);
+                       truncate_inode_pages(inode->i_mapping, inode->i_size);
+                       f2fs_truncate(inode);
+                       up_write(&F2FS_I(inode)->i_mmap_sem);
+               }
+       }
+
+       return 0;
+}
+
+struct iomap_ops f2fs_iomap_ops = {
+       .iomap_begin    = f2fs_iomap_begin,
+       .iomap_end              = f2fs_iomap_end,
+};
+#endif
diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 98f00a3..922d42f 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -60,6 +60,13 @@ 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 30855cf..3463bf9 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,
 };
 
@@ -140,6 +141,7 @@ enum {
        {Opt_fault_injection, "fault_injection=%u"},
        {Opt_lazytime, "lazytime"},
        {Opt_nolazytime, "nolazytime"},
+       {Opt_dax, "dax"},
        {Opt_err, NULL},
 };
 
@@ -482,6 +484,16 @@ static int parse_options(struct super_block *sb, char 
*options)
                        f2fs_msg(sb, KERN_INFO, "noacl options not supported");
                        break;
 #endif
+#ifdef CONFIG_FS_DAX
+               case Opt_dax:
+                       set_opt(sbi, DAX);
+                       break;
+#else
+               case Opt_dax:
+                       f2fs_msg(sb, KERN_INFO, "dax options not supported");
+                       break;
+#endif
+
                case Opt_active_logs:
                        if (args->from && match_int(args, &arg))
                                return -EINVAL;
@@ -966,6 +978,10 @@ static int f2fs_show_options(struct seq_file *seq, struct 
dentry *root)
        if (test_opt(sbi, FAULT_INJECTION))
                seq_puts(seq, ",fault_injection");
 #endif
+#ifdef CONFIG_FS_DAX
+       if (test_opt(sbi, DAX))
+               seq_puts(seq, ",dax");
+#endif
 
        return 0;
 }
-- 
1.8.3.1

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