Message-ID: <8944309f-c525-3238-7609-4f05631ff099@huawei.com>
Date:   Tue, 18 Jul 2017 09:25:01 +0800
From:   Sun Qiuyang <sunqiuyang@...wei.com>
To:     Chao Yu <chao@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
CC:     <jaegeuk@...nel.org>
Subject: Re: [f2fs-dev] [PATCH v6 1/1] f2fs: dax: implement direct access


> On 2017/7/12 17:06, sunqiuyang wrote:
>> From: Qiuyang Sun <sunqiuyang@...wei.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 <sunqiuyang@...wei.com>
>> ---
>> Changlog v5 -> v6:
>> - In f2fs_map_blocks(), optimize the separation of new allocated and old
>>   mapped blocks for the flag F2FS_GET_BLOCK_ZERO, and check the return
>>   value of zeroout;
>> - In f2fs_iomap_begin(), cover the truncation of failed allocation with the
>>   rwsemaphore i_mmap_sem when necessary;
>> - Optimize the order of exception handling in dax_move_data_page().
>>
>> ---
>>  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 +++++
>>  8 files changed, 457 insertions(+), 13 deletions(-)
>>
>> 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);
>
> !(flags & IOMAP_FAULT)?

If (flags & IOMAP_FAULT), the function would have already returned with 
0 at the beginning, and can never reach this line. So !(flag & 
IOMAP_FAULT) must be true here. The logic is similar to that in 
ext4_iomap_end().

Thanks,

>
>> +	}
>> +
>> +	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..7d3e424 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))
>> +		dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
>> +	else
>> +		return;
>
> minor cleanup:
>
> 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
>
> Document option of this new feature in f2fs.txt?
>
> Thanks,
>
>>
>>  	return 0;
>>  }
>>
>
> .
>

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