linux-kernel - Re: [PATCH] f2fs: Fix direct IO handling

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Date:   Thu, 28 Nov 2019 02:34:55 +0000
From:   Shinichiro Kawasaki <shinichiro.kawasaki@....com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     Damien Le Moal <Damien.LeMoal@....com>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chao Yu <yuchao0@...wei.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Javier Gonzalez <javier@...igon.com>
Subject: Re: [PATCH] f2fs: Fix direct IO handling

On Nov 26, 2019 / 15:44, Jaegeuk Kim wrote:
> On 11/26, Damien Le Moal wrote:
> > f2fs_preallocate_blocks() identifies direct IOs using the IOCB_DIRECT
> > flag for a kiocb structure. However, the file system direct IO handler
> > function f2fs_direct_IO() may have decided that a direct IO has to be
> > exececuted as a buffered IO using the function f2fs_force_buffered_io().
> > This is the case for instance for volumes including zoned block device
> > and for unaligned write IOs with LFS mode enabled.
> > 
> > These 2 different methods of identifying direct IOs can result in
> > inconsistencies generating stale data access for direct reads after a
> > direct IO write that is treated as a buffered write. Fix this
> > inconsistency by combining the IOCB_DIRECT flag test with the result
> > of f2fs_force_buffered_io().
> > 
> > Reported-by: Javier Gonzalez <javier@...igon.com>
> > Signed-off-by: Damien Le Moal <damien.lemoal@....com>
> > ---
> >  fs/f2fs/data.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 5755e897a5f0..8ac2d3b70022 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
> >  	int flag;
> >  	int err = 0;
> >  	bool direct_io = iocb->ki_flags & IOCB_DIRECT;
> > +	bool do_direct_io = direct_io &&
> > +		!f2fs_force_buffered_io(inode, iocb, from);
> >  
> >  	/* convert inline data for Direct I/O*/
> >  	if (direct_io) {
> > @@ -1081,7 +1083,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
> >  			return err;
> >  	}
> >  
> > -	if (direct_io && allow_outplace_dio(inode, iocb, from))
> > +	if (do_direct_io && allow_outplace_dio(inode, iocb, from))
> 
> It seems f2fs_force_buffered_io() includes allow_outplace_dio().
> 
> How about this?

Thanks. I confirmed that the issue is gone with your patch.

Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@....com>

> ---
>  fs/f2fs/data.c | 13 -------------
>  fs/f2fs/file.c | 35 +++++++++++++++++++++++++----------
>  2 files changed, 25 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index a034cd0ce021..fc40a72f7827 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1180,19 +1180,6 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>  	int err = 0;
>  	bool direct_io = iocb->ki_flags & IOCB_DIRECT;
>  
> -	/* convert inline data for Direct I/O*/
> -	if (direct_io) {
> -		err = f2fs_convert_inline_inode(inode);
> -		if (err)
> -			return err;
> -	}
> -
> -	if (direct_io && allow_outplace_dio(inode, iocb, from))
> -		return 0;
> -
> -	if (is_inode_flag_set(inode, FI_NO_PREALLOC))
> -		return 0;
> -
>  	map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
>  	map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
>  	if (map.m_len > map.m_lblk)
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index c0560d62dbee..6b32ac6c3382 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3386,18 +3386,33 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  				ret = -EAGAIN;
>  				goto out;
>  			}
> -		} else {
> -			preallocated = true;
> -			target_size = iocb->ki_pos + iov_iter_count(from);
> +			goto write;
> +		}
>  
> -			err = f2fs_preallocate_blocks(iocb, from);
> -			if (err) {
> -				clear_inode_flag(inode, FI_NO_PREALLOC);
> -				inode_unlock(inode);
> -				ret = err;
> -				goto out;
> -			}
> +		if (is_inode_flag_set(inode, FI_NO_PREALLOC))
> +			goto write;
> +
> +		if (iocb->ki_flags & IOCB_DIRECT) {
> +			/* convert inline data for Direct I/O*/
> +			err = f2fs_convert_inline_inode(inode);
> +			if (err)
> +				goto out_err;
> +
> +			if (!f2fs_force_buffered_io(inode, iocb, from))
> +				goto write;
> +		}
> +		preallocated = true;
> +		target_size = iocb->ki_pos + iov_iter_count(from);
> +
> +		err = f2fs_preallocate_blocks(iocb, from);
> +		if (err) {
> +out_err:
> +			clear_inode_flag(inode, FI_NO_PREALLOC);
> +			inode_unlock(inode);
> +			ret = err;
> +			goto out;
>  		}
> +write:
>  		ret = __generic_file_write_iter(iocb, from);
>  		clear_inode_flag(inode, FI_NO_PREALLOC);
>  
> -- 
> 2.19.0.605.g01d371f741-goog
> 

--
Best Regards,
Shin'ichiro Kawasaki