linux-kernel - Re: [f2fs-dev] [PATCH 2/2] f2fs: fix redundant block allocation

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Date:   Fri, 25 Nov 2016 10:16:33 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: fix redundant block allocation

On Sat, Nov 26, 2016 at 12:05:33AM +0800, Chao Yu wrote:
> On 2016/11/12 9:30, Jaegeuk Kim wrote:
> > In direct_IO path of f2fs_file_write_iter(),
> > 1. f2fs_preallocate_blocks(F2FS_GET_BLOCK_PRE_DIO)
> >    -> allocate LBA X
> > 2. f2fs_direct_IO()
> >    -> return 0;
> > 
> > Then,
> > f2fs_write_data_page() will allocate another LBA X+1.
> > 
> > This makes EIO triggered by HM-SMR.
> 
> Good catch, :) how do you find this problem?

I got an error when running fsstres on HM-SMR.

Thanks,

> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> 
> Reviewed-by: Chao Yu <yuchao0@...wei.com>
> 
> > ---
> >  fs/f2fs/data.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 2938311..59203a3 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -658,6 +658,13 @@ static int __allocate_data_block(struct dnode_of_data *dn)
> >  	return 0;
> >  }
> >  
> > +static inline bool __force_buffered_io(struct inode *inode, int rw)
> > +{
> > +	return ((f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode)) ||
> > +			(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);
> > @@ -677,7 +684,10 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
> >  		err = f2fs_convert_inline_inode(inode);
> >  		if (err)
> >  			return err;
> > -		return f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);
> > +		return f2fs_map_blocks(inode, &map, 1,
> > +			__force_buffered_io(inode, WRITE) ?
> > +				F2FS_GET_BLOCK_PRE_AIO :
> > +				F2FS_GET_BLOCK_PRE_DIO);
> >  	}
> >  	if (iocb->ki_pos + iov_iter_count(from) > MAX_INLINE_DATA) {
> >  		err = f2fs_convert_inline_inode(inode);
> > @@ -1769,11 +1779,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
> >  	if (err)
> >  		return err;
> >  
> > -	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
> > -		return 0;
> > -	if (rw == WRITE && test_opt(F2FS_I_SB(inode), LFS))
> > -		return 0;
> > -	if (F2FS_I_SB(inode)->s_ndevs)
> > +	if (__force_buffered_io(inode, rw))
> >  		return 0;
> >  
> >  	trace_f2fs_direct_IO_enter(inode, offset, count, rw);
> >