Re: [PATCH v2] f2fs: add bug_on when f2fs_gc even fails to get one victim

From: Yunlong Song
Date: Mon Nov 06 2017 - 23:04:35 EST


Sorry, misunderstanding, because I think when sync == true, FG_GC does not
check has_not_enough_free_secs, so maybe it does not have to do any gc at all.
For example, if there are 100 segments for f2fs, and 20 segments are full or
valid blocks over fggc_threshold, then it is correct to fail in get victim.


On 2017/11/7 11:26, Jaegeuk Kim wrote:
On 11/07, Yunlong Song wrote:
Because I find that some out-of-free problem is caused by the failure
of get victim target. For example, chao has pointed out that he has
found out a bug when adding this bug_on last week.
That's NOT what I asked. Why not checking FG_GC all the time like this?

f2fs_bug_on(sbi, !total_freed && gc_type == FG_GC);

On 2017/11/7 10:40, Jaegeuk Kim wrote:
On 11/06, Jaegeuk Kim wrote:
On 11/06, Yunlong Song wrote:
Agree.

On 2017/11/3 11:44, Jaegeuk Kim wrote:
On 10/13, Yunlong Song wrote:
This can help us to debug on some corner case.

Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
Signed-off-by: Chao Yu <yuchao0@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..2b03202 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_fggc = 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_fggc = 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_fggc);
Just like this?
That's OK.
I'm not quite sure whether this is really a bug_on case.
Let me make it WARN_ON() for debugging purpose first.
BTW, why is this the special case where BG_GC detects FG_GC?

Thanks,

f2fs_bug_on(sbi, !total_freed && !sync && gc_type == FG_GC);

ret = -ENODATA;
goto stop;
}
--
1.8.5.2
.

--
Thanks,
Yunlong Song

.

--
Thanks,
Yunlong Song

.


--
Thanks,
Yunlong Song