Subject: Re: [PATCH v4 1/1] f2fs: dax: implement direct access
To: Sun Qiuyang <sunqiuyang@huawei.com>, <linux-kernel@vger.kernel.org>,
        <linux-fsdevel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>
References: <1497516975-10604-1-git-send-email-sunqiuyang@huawei.com>
 <94a7d52c-bb63-6006-d5b6-d7b2d8a04fa9@huawei.com>
 <986e088d-05be-a65b-58c0-5dda3f0918a3@huawei.com>
CC: <jaegeuk@kernel.org>
From: Chao Yu <yuchao0@huawei.com>
Message-ID: <2a0e84ae-b060-2a27-b683-3945d22a4fd3@huawei.com>
Date: Fri, 23 Jun 2017 16:27:46 +0800
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Hi Qiuyang,

On 2017/6/23 11:37, Sun Qiuyang wrote:
> Hi Chao,
> 
> Thanks for pointing it out. See below for how to fix this issue.
> 
> 
>> Hi Qiuyang
>>
>> As I tested with pmem, this patch will corrupt f2fs image with generic/051
>> of fstest suit.
>>
>> Could you please take a look at this issue?
>>
>> Thanks,
>>
>> On 2017/6/15 16:56, sunqiuyang wrote:
>>> From: Qiuyang Sun <sunqiuyang@huawei.com>
>>>
>>> This patch implements Direct Access (DAX) in F2FS.
>>>
>>> Signed-off-by: Qiuyang Sun <sunqiuyang@huawei.com>
>>> ---
>>>
>>> Changelog v3 -> v4:
>>>
>>> <data.c>
>>>   In f2fs_iomap_begin():
>>> - For the write branch, if f2fs_map_blocks() returns error (probably due to
>>>   ENOSPC), the allocated blocks beyond original_i_size are truncated.
>>> - For the read branch, use F2FS_GET_BLOCK_FIEMAP instead of READ for
>>>   f2fs_map_blocks(), so that contiguous unwritten blocks can be treated in
>>>   a batch. Accordingly, judge F2FS_MAP_UNWRITTEN before F2FS_MAP_MAPPED for
>>>   iomap->type.
>>>
>>> - Add a call of f2fs_update_time() in f2fs_iomap_end().
>>>
>>> <file.c>
>>> - In f2fs_move_file_range() and f2fs_ioc_defragment(), return -EINVAL for
>>>   DAX files, as the current implementation uses page cache.
>>> - Call f2fs_bug_on() in f2fs_ioc_commit_atomic_write() and
>>>   f2fs_ioc_(release|abort)_volatile_write() when the inode is DAX, which
>>>   should not happen.
>>>
>>> <gc.c>
>>> - Optimize the logic in dax_move_data_page().
>>>
>>> <inode.c>
>>> - Enable setting the S_DAX flag for an inode in f2fs_set_inode_flags().
>>>
>>> The v4 patch is at f2fs-dev-test.
>>>
>>> ---
>>>  fs/f2fs/data.c   | 100 +++++++++++++++++++++++++++++
>>>  fs/f2fs/f2fs.h   |   8 +++
>>>  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, 429 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 7d3af48..58efce0 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2257,3 +2257,103 @@ 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_PRE_DIO);
> 
> The flag F2FS_GET_BLOCK_PRE_DIO will allow allocating new blocks in 
> batch whose physical addresses are not contiguous, and thus user data 
> could be written to incorrect block addresses afterwards, even 
> overwriting metadata blocks and causing FS inconsistency.
> 
> The test "generic/051" can be passed by using F2FS_GET_BLOCK_FIEMAP 
> instead in the write branch here.

Good catch!

As we discussed, F2FS_GET_BLOCK_FIEMAP is designed only for read path, so
F2FS_GET_BLOCK_DIO is preferred.

Thanks,

> 
>>> +		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 91db1d0..f862b6b 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)
>>> @@ -2390,6 +2395,9 @@ 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 6a201c6..e7352a6 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;
>>>
>>> @@ -2080,6 +2198,10 @@ 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;
>>>
>>> @@ -2129,6 +2251,10 @@ 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;
>>> @@ -2368,6 +2494,61 @@ 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;
>>> @@ -2389,7 +2570,10 @@ 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);
>>>  	}
>>> @@ -2437,7 +2621,11 @@ 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;
>>>  }
>>>
>>
>>
>> .
>>
> 
> 
> .
>