Message-ID: <07006a70-afc4-b77c-20da-ff332a4d4cb5@huawei.com>
Date:   Thu, 8 Jun 2017 18:59:10 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Sun Qiuyang <sunqiuyang@...wei.com>, Chao Yu <chao@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
CC:     Jaegeuk Kim <jaegeuk@...nel.org>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: dax: implement direct access

Hi Qiuyang,

On 2017/6/8 17:38, Sun Qiuyang wrote:
> Hi Chao,
> See my comments below.
> 
>> Hi Qiuyang,
>>
>> On 2017/6/7 17:29, sunqiuyang wrote:
>>> From: Qiuyang Sun <sunqiuyang@...wei.com>
>>>
>>> This is a new version of PATCH v2 2/2 with the following minor changes:
>>> - In dax_move_data_page(), the call of allocate_data_block() is changed
>>>   according to the new definition of this function in f2fs-dev, and the
>>>   usage of wio_mutex is removed;
>>> - put_dax() is added in f2fs_iomap_end().
>>>
>>> Signed-off-by: Qiuyang Sun <sunqiuyang@...wei.com>
>>> ---
>>>  fs/f2fs/data.c   |  93 ++++++++++++++++++++++++++
>>>  fs/f2fs/f2fs.h   |   8 +++
>>>  fs/f2fs/file.c   | 194 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>>>  fs/f2fs/gc.c     |  93 ++++++++++++++++++++++++--
>>>  fs/f2fs/inline.c |   4 ++
>>>  fs/f2fs/namei.c  |   6 ++
>>>  fs/f2fs/super.c  |  15 +++++
>>>  7 files changed, 407 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 7d3af48..2285a10 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2257,3 +2257,96 @@ 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;
>>> +	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 we allocated partial blocks in f2fs_map_blocks, then failed to
>> allocate left ones due to ENOSPC or ENOMEM..., it needs to do the
>> truncation according to original i_size.
>>
>>> +	}
>>> +
>>> +	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_MAPPED) {
>>> +			iomap->type = IOMAP_MAPPED;
>>> +		} else if (map.m_flags & F2FS_MAP_UNWRITTEN) {
>>> +			iomap->type = IOMAP_UNWRITTEN;
>>
>> For read path, if blkaddr loaded in dnode is NEW_ADDR, we will set both
>> F2FS_MAP_MAPPED and F2FS_MAP_UNWRITTEN flag in m_flags. With above
>> condition we will set IOMAP_MAPPED instead of IOMAP_UNWRITTEN which may
>> result in incorrectly using of map.m_pblk. So how about reverse above
>> judgment condition to correct it?
> 
> For the read path of f2fs_map_blocks(), if blkaddr == NEW_ADDR, then it 
> will goto sync_out before setting the F2FS_MAP_UNWRITTEN flag. Thus, 
> this flag would never be set in read or write paths here, so I suggest 
> simply removing the judgment about UNWRITTEN.

Yes, you're right, so if we touch fallocated blocks in read path, it will be low
efficient to map just one block one time with f2fs_map_blocks. Could you
consider about using F2FS_GET_BLOCK_FIEMAP to map preallocated blocks in batch?

Thanks,

> 
> Thanks,
> 
>>
>>> +		} 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);
>>
>> Why should we use dax_get_by_host & put_dax here?
>>
>>> +	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 da70964..e3c2ed4 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)
>>> @@ -2387,6 +2392,9 @@ 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 ac8b943..4b070b0 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"
>>> @@ -121,6 +123,64 @@ 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 +496,13 @@ 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 +586,18 @@ 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))
>>> @@ -781,6 +859,19 @@ 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);
>>> @@ -1103,6 +1194,12 @@ 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 current implementation does not apply to DAX files. */
>>> +	if (IS_DAX(inode))
>>> +		return -EINVAL;
>>> +#endif
>>> +
>>>  	if (offset + len >= i_size_read(inode))
>>>  		return -EINVAL;
>>>
>>> @@ -1293,6 +1390,12 @@ 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 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)
>>> @@ -1556,6 +1659,11 @@ 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;
>>
>> Should we allow to enable DAX for inode through F2FS_IOC_SETFLAGS? If it
>> is allowed, we need to check atomic/volatile tag before dax configuring.
>>
>> In additional, we should also check dax file for defragment() and
>> move_range().
>>
>>> +#endif
>>> +
>>>  	if (!inode_owner_or_capable(inode))
>>>  		return -EACCES;
>>>
>>> @@ -1605,6 +1713,11 @@ static int f2fs_ioc_commit_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;
>>>
>>> @@ -1641,6 +1754,11 @@ 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;
>>>
>>> @@ -1676,6 +1794,11 @@ static int f2fs_ioc_release_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;
>>>
>>> @@ -1705,6 +1828,11 @@ static int f2fs_ioc_abort_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;
>>>
>>> @@ -2363,6 +2491,61 @@ 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;
>>> @@ -2384,7 +2567,10 @@ 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);
>>>  	}
>>> @@ -2432,7 +2618,11 @@ 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..3d24afe 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"
>>> @@ -700,6 +701,88 @@ 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 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;
>>> +
>>> +	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 (f2fs_is_atomic_file(inode))
>>> +		return;
>>
>> It must not be an atomic opened file, could we change to add bug_on in
>> the beginning of this function until we support dax for atomic file?
>>
>>> +
>>> +	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_map;
>>> +	old_blkaddr = dn.data_blkaddr;
>>> +	/* This page is already truncated */
>>> +	if (old_blkaddr == NULL_ADDR) {
>>> +		f2fs_put_dnode(&dn);
>>> +		goto out_map;
>>> +	}
>>> +
>>> +	/* 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)
>>
>> Once you allocated new block address, meanwhile sit/ssa info will be
>> changed as well, so, in error path, we should do the recovery with
>> __f2fs_replace_block.
>>
>>> +		goto unlock;
>>> +	map_len = dax_direct_access(dax_dev, pgoff, 1, &kaddr_old, &pfn);
>>> +	if (map_len < 0)
>>> +		goto unlock;
>>> +	err = bdev_dax_pgoff(bdev, SECTOR_FROM_BLOCK(new_blkaddr),
>>> +			PAGE_SIZE, &pgoff);
>>> +	if (err)
>>> +		goto unlock;
>>> +	map_len = dax_direct_access(dax_dev, pgoff, 1, &kaddr_new, &pfn);
>>> +	if (map_len < 0)
>>> +		goto unlock;
>>> +	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);
>>> +	f2fs_put_dnode(&dn);
>>
>> we should include f2fs_put_dnode in error path.
>>
>>> +
>>> +unlock:
>>> +	dax_read_unlock(id);
>>> +out_map:
>>> +	unmap_mapping_range(inode->i_mapping, (loff_t)bidx << PAGE_SHIFT,
>>> +			PAGE_SIZE, 1);
>>> +	up_write(&F2FS_I(inode)->i_mmap_sem);
>>
>> We need release dax_dev here.
>>
>>> +}
>>> +
>>>  static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>  							unsigned int segno, int off)
>>>  {
>>> @@ -818,9 +901,9 @@ 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 +941,9 @@ 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 e4c527c..f858817 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/namei.c b/fs/f2fs/namei.c
>>> index c31b40e..f3edc6c 100644
>>> --- a/fs/f2fs/namei.c
>>> +++ b/fs/f2fs/namei.c
>>> @@ -60,6 +60,12 @@ 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))
>>
>> Coding style.
>>
>> 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 ddd2973..02cda00 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -108,6 +108,7 @@ enum {
>>>  	Opt_fault_injection,
>>>  	Opt_lazytime,
>>>  	Opt_nolazytime,
>>> +	Opt_dax,
>>>  	Opt_err,
>>>  };
>>>
>>> @@ -143,6 +144,7 @@ enum {
>>>  	{Opt_fault_injection, "fault_injection=%u"},
>>>  	{Opt_lazytime, "lazytime"},
>>>  	{Opt_nolazytime, "nolazytime"},
>>> +	{Opt_dax, "dax"},
>>>  	{Opt_err, NULL},
>>>  };
>>>
>>> @@ -490,6 +492,15 @@ 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");
>>
>> s/options/option
>>
>> Thanks,
>>
>>> +			break;
>>> +#endif
>>>  		case Opt_active_logs:
>>>  			if (args->from && match_int(args, &arg))
>>>  				return -EINVAL;
>>> @@ -986,6 +997,10 @@ 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;
>>>  }
>>>
>>
>> .
>>
> 
> 
> .
> 

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