Re: [PATCH] f2fs: add bug_on when f2fs_gc even fails to get one victim

[Yunlong Song <yunlong.song@xxxxxxxxxx>]

Hi, Jay,
    I think it should not happen when need_gc == true but total_freed 
==0, so I add it as bug_on to let it panic at once. And even CHECK_FS is 
closed, this can also printk WARNING message for notice.

On 2017/10/13 7:23, Jaegeuk Kim wrote:
> Hi Yunlong,
>
> On 10/11, Yunlong Song wrote:
> > This can help us to debug on some corner case.
> >
> > Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> > ---
> >   fs/f2fs/gc.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index 197ebf4..960503e 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -986,6 +986,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> >   		.ilist = LIST_HEAD_INIT(gc_list.ilist),
> >   		.iroot = RADIX_TREE_INIT(GFP_NOFS),
> >   	};
> > +	bool need_gc = false;
> >   
> >   	trace_f2fs_gc_begin(sbi->sb, sync, background,
> >   				get_pages(sbi, F2FS_DIRTY_NODES),
> > @@ -1018,8 +1019,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> >   			if (ret)
> >   				goto stop;
> >   		}
> > -		if (has_not_enough_free_secs(sbi, 0, 0))
> > +		if (has_not_enough_free_secs(sbi, 0, 0)) {
> >   			gc_type = FG_GC;
> > +			need_gc = true;
> > +		}
> >   	}
> >   
> >   	/* f2fs_balance_fs doesn't need to do BG_GC in critical path. */
> > @@ -1028,6 +1031,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> >   		goto stop;
> >   	}
> >   	if (!__get_victim(sbi, &segno, gc_type)) {
> > +		f2fs_bug_on(sbi, !total_freed && need_gc);
> How about this, if this is for debugging purpose?
>
> 		if (!total_freed && need_gc)
> 			f2fs_msg(...);
>
> It's not a good way to define a value for f2fs_bug_on(), since it is only
> activated by CHECK_FS config.
>
> Thanks,
>
> >   		ret = -ENODATA;
> >   		goto stop;
> >   	}
> > --
> > 1.8.5.2
> .

--
Thanks,
Yunlong Song