Re: [PATCH v4 4/4] f2fs: stop checkpoint when get a out-of-bounds segment

[Chao Yu <chao@kernel.org>]

On 2024/2/22 10:15, Zhiguo Niu wrote:
> 
> 
> On Thu, Feb 22, 2024 at 9:37 AM Chao Yu <chao@kernel.org <mailto:chao@kernel.org>> wrote:
> 
>     On 2024/2/20 14:11, Zhiguo Niu wrote:
>      > There is low probability that an out-of-bounds segment will be got
>      > on a small-capacity device. In order to prevent subsequent write requests
>      > allocating block address from this invalid segment, which may cause
>      > unexpected issue, stop checkpoint should be performed.
>      >
>      > Also introduce a new stop cp reason: STOP_CP_REASON_NO_SEGMENT.
>      >
>      > Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com <mailto:zhiguo.niu@unisoc.com>>
>      > ---
>      > changes of v4: use more suitable MACRO name according to Chao's suggestions
>      > changes of v3: correct MACRO spelling and update based on the lastes code
>      > ---
>      > ---
>      >   fs/f2fs/segment.c       | 7 ++++++-
>      >   include/linux/f2fs_fs.h | 1 +
>      >   2 files changed, 7 insertions(+), 1 deletion(-)
>      >
>      > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>      > index c25aaec..e42e34c 100644
>      > --- a/fs/f2fs/segment.c
>      > +++ b/fs/f2fs/segment.c
>      > @@ -2665,7 +2665,12 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>      >       if (secno >= MAIN_SECS(sbi)) {
>      >               secno = find_first_zero_bit(free_i->free_secmap,
>      >                                                       MAIN_SECS(sbi));
>      > -             f2fs_bug_on(sbi, secno >= MAIN_SECS(sbi));
>      > +             if (secno >= MAIN_SECS(sbi)) {
>      > +                     f2fs_stop_checkpoint(sbi, false,
>      > +                             STOP_CP_REASON_NO_SEGMENT);
> 
>     We should relocate stop_checkpoint(sbi, false, STOP_CP_REASON_NO_SEGMENT) outside
>     segmap_lock spinlock, due to it may sleep in f2fs_flush_merged_writes().
> 
> Indeed it is. How about the following fix?
> @@ -2665,11 +2665,7 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>          if (secno >= MAIN_SECS(sbi)) {
>                  secno = find_first_zero_bit(free_i->free_secmap,
>                                                          MAIN_SECS(sbi));
> -               if (secno >= MAIN_SECS(sbi)) {
> -                       f2fs_stop_checkpoint(sbi, false,
> -                               STOP_CP_REASON_NO_SEGMENT);
> -                       f2fs_bug_on(sbi, 1);
> -               }
> +               f2fs_bug_on(sbi, secno >= MAIN_SECS(sbi));
>          }
>          segno = GET_SEG_FROM_SEC(sbi, secno);
>          zoneno = GET_ZONE_FROM_SEC(sbi, secno);
> @@ -2700,6 +2696,8 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>          __set_inuse(sbi, segno);
>          *newseg = segno;
>          spin_unlock(&free_i->segmap_lock);
> +       if (secno >= MAIN_SECS(sbi))
> +               f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_NO_SEGMENT);

How about this?

---
  fs/f2fs/segment.c | 12 +++++++++---
  1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index d0209ea77dd2..8edc42071e6f 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2646,6 +2646,7 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
  	unsigned int old_zoneno = GET_ZONE_FROM_SEG(sbi, *newseg);
  	bool init = true;
  	int i;
+	int ret = 0;

  	spin_lock(&free_i->segmap_lock);

@@ -2671,9 +2672,8 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
  		secno = find_first_zero_bit(free_i->free_secmap,
  							MAIN_SECS(sbi));
  		if (secno >= MAIN_SECS(sbi)) {
-			f2fs_stop_checkpoint(sbi, false,
-				STOP_CP_REASON_NO_SEGMENT);
-			f2fs_bug_on(sbi, 1);
+			ret = -ENOSPC;
+			goto out_unlock;
  		}
  	}
  	segno = GET_SEG_FROM_SEC(sbi, secno);
@@ -2704,7 +2704,13 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
  	f2fs_bug_on(sbi, test_bit(segno, free_i->free_segmap));
  	__set_inuse(sbi, segno);
  	*newseg = segno;
+out_unlock:
  	spin_unlock(&free_i->segmap_lock);
+
+	if (ret) {
+		f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_NO_SEGMENT);
+		f2fs_bug_on(sbi, 1);
+	}
  }

  static void reset_curseg(struct f2fs_sb_info *sbi, int type, int modified)
-- 
2.40.1

> 
>     Thanks,
> 
>      > +                     f2fs_bug_on(sbi, 1);
>      > +             }
>      > +
>      >       }
>      >       segno = GET_SEG_FROM_SEC(sbi, secno);
>      >       zoneno = GET_ZONE_FROM_SEC(sbi, secno);
>      > diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>      > index 9b69c50..755e9a4 100644
>      > --- a/include/linux/f2fs_fs.h
>      > +++ b/include/linux/f2fs_fs.h
>      > @@ -75,6 +75,7 @@ enum stop_cp_reason {
>      >       STOP_CP_REASON_CORRUPTED_SUMMARY,
>      >       STOP_CP_REASON_UPDATE_INODE,
>      >       STOP_CP_REASON_FLUSH_FAIL,
>      > +     STOP_CP_REASON_NO_SEGMENT,
>      >       STOP_CP_REASON_MAX,
>      >   };
>      >
>