From: Qiuyang Sun <sunqiuy...@huawei.com>

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 <sunqiuy...@huawei.com>
---
Changlog v6 -> v7:
- Document the mount option "dax" for this feature in f2fs.txt
- Minor cleanup in dax_move_data_page()

---
 Documentation/filesystems/f2fs.txt |   2 +
 fs/f2fs/data.c                     | 132 +++++++++++++++++++++++--
 fs/f2fs/f2fs.h                     |   9 ++
 fs/f2fs/file.c                     | 192 ++++++++++++++++++++++++++++++++++++-
 fs/f2fs/gc.c                       | 105 +++++++++++++++++++-
 fs/f2fs/inline.c                   |   4 +
 fs/f2fs/inode.c                    |   8 +-
 fs/f2fs/namei.c                    |   5 +
 fs/f2fs/super.c                    |  15 +++
 9 files changed, 459 insertions(+), 13 deletions(-)

diff --git a/Documentation/filesystems/f2fs.txt 
b/Documentation/filesystems/f2fs.txt
index 273ccb2..c86c421 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -164,6 +164,8 @@ io_bits=%u             Set the bit size of write IO 
requests. It should be set
                        with "mode=lfs".
 usrquota               Enable plain user disk quota accounting.
 grpquota               Enable plain group disk quota accounting.
+dax                    Use direct access (no page cache). See
+                       Documentation/filesystems/dax.txt.
 
 
================================================================================
 DEBUGFS ENTRIES
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 87c1f41..26b908a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -910,6 +910,15 @@ 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++;
@@ -938,7 +947,8 @@ int f2fs_map_blocks(struct inode *inode, struct 
f2fs_map_blocks *map,
                                                blkaddr != NEW_ADDR)
                                goto sync_out;
                }
-       }
+       } else if (flag == F2FS_GET_BLOCK_ZERO && map->m_flags & F2FS_MAP_NEW)
+               goto sync_out;
 
        if (flag == F2FS_GET_BLOCK_PRE_AIO)
                goto skip;
@@ -996,6 +1006,12 @@ 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);
+               err = sb_issue_zeroout(inode->i_sb, map->m_pblk,
+                               map->m_len, GFP_NOFS);
+       }
        f2fs_put_dnode(&dn);
 unlock_out:
        if (create) {
@@ -1808,16 +1824,19 @@ static int f2fs_write_data_pages(struct address_space 
*mapping,
        return 0;
 }
 
-static void f2fs_write_failed(struct address_space *mapping, loff_t to)
+static void f2fs_write_failed(struct address_space *mapping, loff_t to,
+                                                               bool lock)
 {
        struct inode *inode = mapping->host;
        loff_t i_size = i_size_read(inode);
 
        if (to > i_size) {
-               down_write(&F2FS_I(inode)->i_mmap_sem);
+               if (lock)
+                       down_write(&F2FS_I(inode)->i_mmap_sem);
                truncate_pagecache(inode, i_size);
                truncate_blocks(inode, i_size, true);
-               up_write(&F2FS_I(inode)->i_mmap_sem);
+               if (lock)
+                       up_write(&F2FS_I(inode)->i_mmap_sem);
        }
 }
 
@@ -2000,7 +2019,7 @@ static int f2fs_write_begin(struct file *file, struct 
address_space *mapping,
 
 fail:
        f2fs_put_page(page, 1);
-       f2fs_write_failed(mapping, pos + len);
+       f2fs_write_failed(mapping, pos + len, true);
        return err;
 }
 
@@ -2077,7 +2096,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct 
iov_iter *iter)
                if (err > 0)
                        set_inode_flag(inode, FI_UPDATE_WRITE);
                else if (err < 0)
-                       f2fs_write_failed(mapping, offset + count);
+                       f2fs_write_failed(mapping, offset + count, true);
        }
 
        trace_f2fs_direct_IO_exit(inode, offset, count, rw, err);
@@ -2274,3 +2293,104 @@ 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)
+                               f2fs_write_failed(inode->i_mapping,
+                                               offset + length,
+                                               !(flags & IOMAP_FAULT));
+               }
+       }
+
+       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,
+                                                                       true);
+       }
+
+       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 94a88b2..0bbe011 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -91,6 +91,11 @@ struct f2fs_fault_info {
 #define F2FS_MOUNT_LFS                 0x00040000
 #define F2FS_MOUNT_USRQUOTA            0x00080000
 #define F2FS_MOUNT_GRPQUOTA            0x00100000
+#ifdef CONFIG_FS_DAX
+#define F2FS_MOUNT_DAX                 0x00200000 /* 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)
@@ -479,6 +484,7 @@ 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.
@@ -2437,6 +2443,9 @@ 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 a0e6d2c..0e62e97 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;
 }
 
@@ -519,6 +587,17 @@ 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))
@@ -799,6 +878,18 @@ 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);
@@ -1121,6 +1212,11 @@ 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;
 
@@ -1311,6 +1407,11 @@ 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)
@@ -1581,6 +1682,10 @@ 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;
 
@@ -1630,6 +1735,9 @@ 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;
 
@@ -1666,6 +1774,10 @@ 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;
 
@@ -1701,6 +1813,9 @@ 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;
 
@@ -1730,6 +1845,9 @@ 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;
 
@@ -2144,6 +2262,10 @@ 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;
 
@@ -2193,6 +2315,10 @@ 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;
@@ -2434,6 +2560,61 @@ 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;
@@ -2455,7 +2636,10 @@ 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);
        }
@@ -2504,7 +2688,11 @@ 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..289d748 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -700,6 +700,101 @@ 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 (!check_valid_map(sbi, segno, off))
+               return;
+
+       if (!blk_queue_dax(bdev->bd_queue))
+               return;
+
+       dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+
+       if (!down_write_trylock(&F2FS_I(inode)->i_mmap_sem))
+               goto release;
+
+       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);
+release:
+       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 +913,9 @@ 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 +953,9 @@ 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 6cd312a..7741461 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 760d852..afc52e0 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -70,6 +70,11 @@ 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 32e4c02..aefe931 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -109,6 +109,7 @@ enum {
        Opt_nolazytime,
        Opt_usrquota,
        Opt_grpquota,
+       Opt_dax,
        Opt_err,
 };
 
@@ -146,6 +147,7 @@ enum {
        {Opt_nolazytime, "nolazytime"},
        {Opt_usrquota, "usrquota"},
        {Opt_grpquota, "grpquota"},
+       {Opt_dax, "dax"},
        {Opt_err, NULL},
 };
 
@@ -399,6 +401,15 @@ static int parse_options(struct super_block *sb, char 
*options)
                                        "quota operations 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 option not supported");
+                       break;
+#endif
                default:
                        f2fs_msg(sb, KERN_ERR,
                                "Unrecognized mount option \"%s\" or missing 
value",
@@ -814,6 +825,10 @@ static int f2fs_show_options(struct seq_file *seq, struct 
dentry *root)
        if (test_opt(sbi, GRPQUOTA))
                seq_puts(seq, ",grpquota");
 #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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