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Subject: Re: [PATCH v2] f2fs: add nowait aio support
To:     Hyunchul Lee <hyc.lee@gmail.com>, Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <kernel-team@lge.com>,
        Christoph Hellwig <hch@lst.de>,
        Goldwyn Rodrigues <rgoldwyn@suse.com>,
        Hyunchul Lee <cheol.lee@lge.com>
References: <1520493679-17778-1-git-send-email-hyc.lee@gmail.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <40c19e83-cb8c-c9b6-4aa5-74b56f01595f@huawei.com>
Date:   Thu, 8 Mar 2018 17:50:45 +0800
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On 2018/3/8 15:21, Hyunchul Lee wrote:
> From: Hyunchul Lee <cheol.lee@lge.com>
> 
> This patch adds nowait aio support[1].
> 
> Return EAGAIN if any of the following checks fail for direct I/O:
>   - i_rwsem is not lockable
>   - Blocks are not allocated at the write location
> 
> And xfstests generic/471 is passed.
> 
>  [1]: 6be96d "Introduce RWF_NOWAIT and FMODE_AIO_NOWAIT"
> 
> Signed-off-by: Hyunchul Lee <cheol.lee@lge.com>
> ---
> Changes from v1:
>  - Return EGAIN if dio_rwsem is not lockable in f2fs_direct_IO
>  - Fix the wrong calculation of last_lblk in f2fs_overwrite_io 
> 
>  fs/f2fs/data.c | 47 +++++++++++++++++++++++++++++++++++++----------
>  fs/f2fs/f2fs.h |  8 ++++++++
>  fs/f2fs/file.c | 35 +++++++++++++++++++++++++++++------
>  3 files changed, 74 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 6c3c978..b27ea1e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -839,13 +839,6 @@ static int __allocate_data_block(struct dnode_of_data *dn, int seg_type)
>  	return 0;
>  }
>  
> -static inline bool __force_buffered_io(struct inode *inode, int rw)
> -{
> -	return (f2fs_encrypted_file(inode) ||
> -			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
> -			F2FS_I_SB(inode)->s_ndevs);
> -}
> -
>  int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  {
>  	struct inode *inode = file_inode(iocb->ki_filp);
> @@ -877,7 +870,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  
>  	if (direct_io) {
>  		map.m_seg_type = rw_hint_to_seg_type(iocb->ki_hint);
> -		flag = __force_buffered_io(inode, WRITE) ?
> +		flag = f2fs_force_buffered_io(inode, WRITE) ?
>  					F2FS_GET_BLOCK_PRE_AIO :
>  					F2FS_GET_BLOCK_PRE_DIO;
>  		goto map_blocks;
> @@ -1121,6 +1114,31 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>  	return err;
>  }
>  
> +bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len)
> +{
> +	struct f2fs_map_blocks map;
> +	block_t last_lblk;
> +	int err;
> +
> +	if (pos + len > i_size_read(inode))
> +		return false;
> +
> +	map.m_lblk = F2FS_BYTES_TO_BLK(pos);
> +	map.m_next_pgofs = 0;

Sorry, additional minor comments,

map.m_next_pgofs = NULL;

> +	map.m_next_extent = NULL;
> +	map.m_seg_type = NO_CHECK_TYPE;
> +	last_lblk = F2FS_BYTES_TO_BLK(pos + len - 1) + 1;

F2FS_BLK_ALIGN(pos + len)?

> +
> +	while (map.m_lblk < last_lblk) {
> +		map.m_len = last_lblk - map.m_lblk;
> +		err = f2fs_map_blocks(inode, &map, 0, 0);

f2fs_map_blocks(.., F2FS_GET_BLOCK_DEFAULT);

Thanks,

> +		if (err || map.m_len == 0)
> +			return false;
> +		map.m_lblk += map.m_len;
> +	}
> +	return true;
> +}
> +
>  static int __get_data_block(struct inode *inode, sector_t iblock,
>  			struct buffer_head *bh, int create, int flag,
>  			pgoff_t *next_pgofs, int seg_type)
> @@ -2306,7 +2324,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  	if (err)
>  		return err;
>  
> -	if (__force_buffered_io(inode, rw))
> +	if (f2fs_force_buffered_io(inode, rw))
>  		return 0;
>  
>  	trace_f2fs_direct_IO_enter(inode, offset, count, rw);
> @@ -2314,7 +2332,15 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  	if (rw == WRITE && whint_mode == WHINT_MODE_OFF)
>  		iocb->ki_hint = WRITE_LIFE_NOT_SET;
>  
> -	down_read(&F2FS_I(inode)->dio_rwsem[rw]);
> +	if (!down_read_trylock(&F2FS_I(inode)->dio_rwsem[rw])) {
> +		if (iocb->ki_flags & IOCB_NOWAIT) {
> +			iocb->ki_hint = hint;
> +			err = -EAGAIN;
> +			goto out;
> +		}
> +		down_read(&F2FS_I(inode)->dio_rwsem[rw]);
> +	}
> +
>  	err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio);
>  	up_read(&F2FS_I(inode)->dio_rwsem[rw]);
>  
> @@ -2330,6 +2356,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  		}
>  	}
>  
> +out:
>  	trace_f2fs_direct_IO_exit(inode, offset, count, rw, err);
>  
>  	return err;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index f6dc706..351226e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2875,6 +2875,7 @@ 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
> +bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len);
>  
>  /*
>   * gc.c
> @@ -3259,4 +3260,11 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
>  #endif
>  }
>  
> +static inline bool f2fs_force_buffered_io(struct inode *inode, int rw)
> +{
> +	return (f2fs_encrypted_file(inode) ||
> +			(rw == WRITE && test_opt(F2FS_I_SB(inode), LFS)) ||
> +			F2FS_I_SB(inode)->s_ndevs);
> +}
> +
>  #endif
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6a202e5..1051edd 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -479,6 +479,9 @@ static int f2fs_file_open(struct inode *inode, struct file *filp)
>  
>  	if (err)
>  		return err;
> +
> +	filp->f_mode |= FMODE_NOWAIT;
> +
>  	return dquot_file_open(inode, filp);
>  }
>  
> @@ -2895,7 +2898,15 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
>  		return -EIO;
>  
> -	inode_lock(inode);
> +	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
> +		return -EINVAL;
> +
> +	if (!inode_trylock(inode)) {
> +		if (iocb->ki_flags & IOCB_NOWAIT)
> +			return -EAGAIN;
> +		inode_lock(inode);
> +	}
> +
>  	ret = generic_write_checks(iocb, from);
>  	if (ret > 0) {
>  		int err;
> @@ -2903,11 +2914,23 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  		if (iov_iter_fault_in_readable(from, iov_iter_count(from)))
>  			set_inode_flag(inode, FI_NO_PREALLOC);
>  
> -		err = f2fs_preallocate_blocks(iocb, from);
> -		if (err) {
> -			clear_inode_flag(inode, FI_NO_PREALLOC);
> -			inode_unlock(inode);
> -			return err;
> +		if ((iocb->ki_flags & IOCB_NOWAIT) &&
> +			(iocb->ki_flags & IOCB_DIRECT)) {
> +				if (!f2fs_overwrite_io(inode, iocb->ki_pos,
> +						iov_iter_count(from)) ||
> +					f2fs_has_inline_data(inode) ||
> +					f2fs_force_buffered_io(inode, WRITE)) {
> +						inode_unlock(inode);
> +						return -EAGAIN;
> +				}
> +
> +		} else {
> +			err = f2fs_preallocate_blocks(iocb, from);
> +			if (err) {
> +				clear_inode_flag(inode, FI_NO_PREALLOC);
> +				inode_unlock(inode);
> +				return err;
> +			}
>  		}
>  		blk_start_plug(&plug);
>  		ret = __generic_file_write_iter(iocb, from);
>