linux-kernel - Re: [PATCH v3] F2FS: invalidate META

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Date:   Tue, 02 Nov 2021 15:49:52 +0900
From:   Hyeong-Jun Kim <hj514.kim@...sung.com>
To:     Chao Yu <chao@...nel.org>, Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     sj1557.seo@...sung.com, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] F2FS: invalidate META_MAPPING before IPU/DIO write

On Tue, 2021-11-02 at 14:47 +0800, Chao Yu wrote:
> On 2021/11/2 12:59, Hyeong-Jun Kim wrote:
> > Encrypted pages during GC are read and cached in META_MAPPING.
> > However, due to cached pages in META_MAPPING, there is an issue
> > where
> > newly written pages are lost by IPU or DIO writes.
> > 
> > Thread A - f2fs_gc()            Thread B
> > /* phase 3 */
> > down_write(i_gc_rwsem)
> > ra_data_block()       ---- (a)
> > up_write(i_gc_rwsem)
> >                                  f2fs_direct_IO() :
> >                                   - down_read(i_gc_rwsem)
> >                                   - __blockdev_direct_io()
> >                                   - get_data_block_dio_write()
> >                                   - f2fs_dio_submit_bio()  ---- (b)
> >                                   - up_read(i_gc_rwsem)
> > /* phase 4 */
> > down_write(i_gc_rwsem)
> > move_data_block()     ---- (c)
> > up_write(i_gc_rwsem)
> > 
> > (a) In phase 3 of f2fs_gc(), up-to-date page is read from storage
> > and
> >      cached in META_MAPPING.
> > (b) In thread B, writing new data by IPU or DIO write on same
> > blkaddr as
> >      read in (a). cached page in META_MAPPING become out-dated.
> > (c) In phase 4 of f2fs_gc(), out-dated page in META_MAPPING is
> > copied to
> >      new blkaddr. In conclusion, the newly written data in (b) is
> > lost.
> > 
> > To address this issue, invalidating pages in META_MAPPING before
> > IPU or
> > DIO write.
> > 
> > ---
> > v3:
> >   - Use sbi instead of fio->sbi in f2fs_inplace_write_data()
> > v2:
> >   - Update patch description with race condition
> 
> 
> 
> > Fixes: 6aa58d8ad20a ("f2fs: readahead encrypted block during GC")
> > Signed-off-by: Hyeong-Jun Kim <
> > hj514.kim@...sung.com
> > >
> > ---
> 
> Change log should be attached here, otherwise Fixes & Signed-off-by
> tag will be lost
> after applying this patch.
> 
> Thanks,
> 
Thanks for your comment.
Should I re-send this patch?

Thanks,
> >   fs/f2fs/data.c    | 2 ++
> >   fs/f2fs/segment.c | 3 +++
> >   2 files changed, 5 insertions(+)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 74e1a350c1d8..9f754aaef558 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1708,6 +1708,8 @@ int f2fs_map_blocks(struct inode *inode,
> > struct f2fs_map_blocks *map,
> >   		 */
> >   		f2fs_wait_on_block_writeback_range(inode,
> >   						map->m_pblk, map-
> > >m_len);
> > +		invalidate_mapping_pages(META_MAPPING(sbi),
> > +						map->m_pblk, map-
> > >m_pblk);
> >   
> >   		if (map->m_multidev_dio) {
> >   			block_t blk_addr = map->m_pblk;
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 526423fe84ce..df9ed75f0b7a 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -3652,6 +3652,9 @@ int f2fs_inplace_write_data(struct
> > f2fs_io_info *fio)
> >   		goto drop_bio;
> >   	}
> >   
> > +	invalidate_mapping_pages(META_MAPPING(sbi),
> > +				fio->new_blkaddr, fio->new_blkaddr);
> > +
> >   	stat_inc_inplace_blocks(fio->sbi);
> >   
> >   	if (fio->bio && !(SM_I(sbi)->ipu_policy & (1 <<
> > F2FS_IPU_NOCACHE)))
> > 
> 
>