Re: [PATCH] f2fs: let f2fs also gc atomic file to avoid loop gc

[Yunlong Song]

How about add file_write_and_wait_range in __write_node_page as following:
if (atomic && !test_opt(sbi, NOBARRIER)) {
    file_write_and_wait_range(file, 0, LLONG_MAX);
    fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
}

The all the GCed data will be flushed to non-volatile before last node 
write with REQ_PREFLUSH | REQ_FUA.

On 2017/11/17 11:20, Chao Yu wrote:
> On 2017/11/17 11:04, Yunlong Song wrote:
> > The atomic commit will trigger:
> >       -f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true)
> >           -file_write_and_wait_range(file, 0, LLONG_MAX)
> >           -fsync_node_pages
> >               -__write_node_page
> >                   -REQ_PREFLUSH | REQ_FUA
> >
> > So data is flushed to non-volatile before  last node write with > REQ_PREFLUSH | REQ_FUA,
> I mean GCed data.
>
> - file_write_and_wait_range
> 					- move_data_block
> 					 - f2fs_submit_page_write
> 					  - f2fs_update_data_blkaddr
> 					   - set_page_dirty
>   - fsync_node_pages
>
> Thanks,
>
> > we do not need to worry about the inconsistent problem. Right?
> >
> > On 2017/11/17 10:49, Chao Yu wrote:
> > > On 2017/11/17 8:58, Yunlong Song wrote:
> > > > Is there any problem if just deleting the judgement condition in this patch?
> > > IIRC, dirty node comes from data segment GC can be writebacked & flushed during
> > > atomic commit, but related data will still be in inner bio cache, after later
> > > SPOR, data would be inconsistent.
> > >
> > > Thanks,
> > >
> > > > On 2017/11/8 17:28, Chao Yu wrote:
> > > > > On 2017/11/8 10:34, Yunlong Song wrote:
> > > > > > If some files are opened with atomic flag and have not commited yet, at
> > > > > > the same time, if all the target victim segments have at least one page
> > > > > > of these atomic files, then f2fs gc will fail to do gc and hangs in the
> > > > > > process of go to gc_more, since gc_date_segment will not move any data
> > > > > > and get_valid_blocks will never be 0, then do_garbage_collect will
> > > > > > always return 0.
> > > > > Oh, I added this judgment condition to avoid ruining atomic write by data
> > > > > GC, could we find another way to solve this issue? BTW, if there is direct
> > > > > IO, we will also skip data segment GC.
> > > > >
> > > > > Thanks,
> > > > >
> > > > > > Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> > > > > > ---
> > > > > >     fs/f2fs/gc.c | 6 ------
> > > > > >     1 file changed, 6 deletions(-)
> > > > > >
> > > > > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > > > > index 5d5bba4..3fdcd04 100644
> > > > > > --- a/fs/f2fs/gc.c
> > > > > > +++ b/fs/f2fs/gc.c
> > > > > > @@ -621,9 +621,6 @@ static void move_data_block(struct inode *inode, block_t bidx,
> > > > > >     	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
> > > > > >     		goto out;
> > > > > >     
> > > > > > -	if (f2fs_is_atomic_file(inode))
> > > > > > -		goto out;
> > > > > > -
> > > > > >     	set_new_dnode(&dn, inode, NULL, NULL, 0);
> > > > > >     	err = get_dnode_of_data(&dn, bidx, LOOKUP_NODE);
> > > > > >     	if (err)
> > > > > > @@ -718,9 +715,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
> > > > > >     	if (!check_valid_map(F2FS_I_SB(inode), segno, off))
> > > > > >     		goto out;
> > > > > >     
> > > > > > -	if (f2fs_is_atomic_file(inode))
> > > > > > -		goto out;
> > > > > > -
> > > > > >     	if (gc_type == BG_GC) {
> > > > > >     		if (PageWriteback(page))
> > > > > >     			goto out;
> > > > > .
> > > .
>
> .

--
Thanks,
Yunlong Song