Re: [f2fs-dev] [PATCH] f2fs: fix data corruption issue with hardware encryption

[Jaegeuk Kim]

On 10/10, Jaegeuk Kim wrote:
> On 10/11, Sahitya Tummala wrote:
> > On Wed, Oct 10, 2018 at 02:34:02PM -0700, Jaegeuk Kim wrote:
> > > On 10/10, Sahitya Tummala wrote:
> > > > Direct IO can be used in case of hardware encryption. The following
> > > > scenario results into data corruption issue in this path -
> > > > 
> > > > Thread A -                          Thread B-
> > > > -> write file#1 in direct IO
> > > >                                     -> GC gets kicked in
> > > >                                     -> GC submitted bio on meta mapping
> > > > 				       for file#1, but pending completion
> > > > -> write file#1 again with new data
> > > >    in direct IO
> > > >                                     -> GC bio gets completed now
> > > >                                     -> GC writes old data to the new
> > > >                                        location and thus file#1 is
> > > > 				       corrupted.
> > > > 
> > > > Fix this by submitting and waiting for pending io on meta mapping
> > > > for direct IO case in f2fs_map_blocks().
> > > > 
> > > > Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
> > > > ---
> > > >  fs/f2fs/data.c | 12 ++++++++++++
> > > >  1 file changed, 12 insertions(+)
> > > > 
> > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > > index 9ef6f1f..7b2fef0 100644
> > > > --- a/fs/f2fs/data.c
> > > > +++ b/fs/f2fs/data.c
> > > > @@ -1028,6 +1028,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
> > > >  		map->m_pblk = ei.blk + pgofs - ei.fofs;
> > > >  		map->m_len = min((pgoff_t)maxblocks, ei.fofs + ei.len - pgofs);
> > > >  		map->m_flags = F2FS_MAP_MAPPED;
> > > > +		/* for HW encryption, but to avoid potential issue in future */
> > > > +		if (flag == F2FS_GET_BLOCK_DIO) {
> > > > +			blkaddr = map->m_pblk;
> > > > +			for (; blkaddr < map->m_pblk + map->m_len; blkaddr++)
> > > > +				f2fs_wait_on_block_writeback(sbi, blkaddr);
> > > 
> > > Do we need this? IIRC, DIO would give create=1.
> > 
> > Yes, we need it. When we are overwriting an existing file, DIO calls
> > f2fs_map_blocks() with create=0. From the DIO code, I see that this happens
> > because blockdev_direct_IO() passes this dio flag DIO_SKIP_HOLES. And then
> > in get_more_blocks(), below code updates create=0, when we are overwriting
> > an existing file.
> > 
> >                 create = dio->op == REQ_OP_WRITE;
> >                 if (dio->flags & DIO_SKIP_HOLES) {
> >                         if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
> >                                                         i_blkbits))
> >                                 create = 0;
> >                 }
> > 
> >                 ret = (*sdio->get_block)(dio->inode, fs_startblk,
> >                                                 map_bh, create);
> > 
> 
> Got it.
> How about this?
> 

Sorry, this is v2.