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

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Agree.

On 2017/11/10 1:59, Jaegeuk Kim wrote:
On 11/08, Yunlong Song wrote:
So we should use f2fs_bug_on(sbi, !total_freed && !sync && gc_type ==
FG_GC);
f2fs_bug_on(sbi, !total_freed && has_not_enough_free_secs(sbi, 0, 0)); ?

On 2017/11/7 14:56, Chao Yu wrote:
On 2017/11/7 12:01, Yunlong Song wrote:
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);
ioctl(F2FS_IOC_GARBAGE_COLLECT, &1) will simply trigger this bug_on, so we
have to check the conditon only when we run out-of-free-space?

Thanks,

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

.


--
Thanks,
Yunlong Song





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