Re: [f2fs-dev] [PATCH 2/2 v2] f2fs: avoid to select pinned section during checkpoint=disable

[Chao Yu <chao@kernel.org>]

On 2022/5/5 4:22, Jaegeuk Kim wrote:
> The f2fs_gc uses a bitmap to indicate pinned sections, but when disabling
> chckpoint, we call f2fs_gc() with NULL_SEGNO which selects the same dirty
> segment as a victim all the time, resulting in checkpoint=disable failure.
> Let's pick another one, if we fail to collect it.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> 
>   Change log from v1:
>    - keep sync condition to stop GC
> 
>   fs/f2fs/gc.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 4d47723523c3..441190ab8593 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1838,10 +1838,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>   	if (gc_type == FG_GC)
>   		sbi->cur_victim_sec = NULL_SEGNO;
>   
> -	if (sync)
> -		goto stop;
> -
> -	if (!has_not_enough_free_secs(sbi, sec_freed, 0))
> +	if ((!has_not_enough_free_secs(sbi, sec_freed, 0) || sync) && seg_freed)

Wait, it doesn't make sense that it needs to migrate one section successfully
when there is enough free sections, e.g. for background GC case.

I doubt above implementation may force bggc to migrate all dirty sections?
due to seg_freed will always be zero, because it increases only if gc_type
is FG_GC?

		if (gc_type == FG_GC &&
				get_valid_blocks(sbi, segno, false) == 0)
			seg_freed++;

And I didn't see there is one or combinations of parameters can indicate
meaning: "it needs to migrate one section at least before exit", so how
about introducing another parameter for this requirement?

From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Sat, 30 Apr 2022 03:27:20 -0700
Subject: [PATCH] f2fs: avoid to select pinned section during
  checkpoint=disable

The f2fs_gc uses a bitmap to indicate pinned sections, but when disabling
chckpoint, we call f2fs_gc() with NULL_SEGNO which selects the same dirty
segment as a victim all the time, resulting in checkpoint=disable failure.
Let's pick another one, if we fail to collect it.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
  fs/f2fs/f2fs.h    |  2 +-
  fs/f2fs/file.c    |  8 ++++----
  fs/f2fs/gc.c      | 17 ++++++++++++-----
  fs/f2fs/segment.c |  2 +-
  fs/f2fs/super.c   |  2 +-
  5 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 56adc3b68e14..0f8c426aed50 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3787,7 +3787,7 @@ int f2fs_start_gc_thread(struct f2fs_sb_info *sbi);
  void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi);
  block_t f2fs_start_bidx_of_node(unsigned int node_ofs, struct inode *inode);
  int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, bool background, bool force,
-			unsigned int segno);
+			unsigned int segno, unsigned int nr_section);
  void f2fs_build_gc_manager(struct f2fs_sb_info *sbi);
  int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count);
  int __init f2fs_create_garbage_collection_cache(void);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index e4cf8b7b23aa..07d2fa6c774b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1684,7 +1684,7 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
  		if (has_not_enough_free_secs(sbi, 0,
  			GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi)))) {
  			f2fs_down_write(&sbi->gc_lock);
-			err = f2fs_gc(sbi, true, false, false, NULL_SEGNO);
+			err = f2fs_gc(sbi, true, false, false, NULL_SEGNO, 0);
  			if (err && err != -ENODATA && err != -EAGAIN)
  				goto out_err;
  		}
@@ -2472,7 +2472,7 @@ static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
  		f2fs_down_write(&sbi->gc_lock);
  	}

-	ret = f2fs_gc(sbi, sync, true, false, NULL_SEGNO);
+	ret = f2fs_gc(sbi, sync, true, false, NULL_SEGNO, 0);
  out:
  	mnt_drop_write_file(filp);
  	return ret;
@@ -2509,7 +2509,7 @@ static int __f2fs_ioc_gc_range(struct file *filp, struct f2fs_gc_range *range)
  	}

  	ret = f2fs_gc(sbi, range->sync, true, false,
-				GET_SEGNO(sbi, range->start));
+				GET_SEGNO(sbi, range->start), 0);
  	if (ret) {
  		if (ret == -EBUSY)
  			ret = -EAGAIN;
@@ -2966,7 +2966,7 @@ static int f2fs_ioc_flush_device(struct file *filp, unsigned long arg)
  		sm->last_victim[GC_CB] = end_segno + 1;
  		sm->last_victim[GC_GREEDY] = end_segno + 1;
  		sm->last_victim[ALLOC_NEXT] = end_segno + 1;
-		ret = f2fs_gc(sbi, true, true, true, start_segno);
+		ret = f2fs_gc(sbi, true, true, true, start_segno, 0);
  		if (ret == -EAGAIN)
  			ret = 0;
  		else if (ret < 0)
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 4d47723523c3..2364ffe6bbbf 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -142,7 +142,7 @@ static int gc_thread_func(void *data)
  			sync_mode = false;

  		/* if return value is not zero, no victim was selected */
-		if (f2fs_gc(sbi, sync_mode, !foreground, false, NULL_SEGNO))
+		if (f2fs_gc(sbi, sync_mode, !foreground, false, NULL_SEGNO, 0))
  			wait_ms = gc_th->no_gc_sleep_time;

  		if (foreground)
@@ -1751,7 +1751,8 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
  }

  int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
-			bool background, bool force, unsigned int segno)
+			bool background, bool force, unsigned int segno,
+			unsigned int nr_section)
  {
  	int gc_type = sync ? FG_GC : BG_GC;
  	int sec_freed = 0, seg_freed = 0, total_freed = 0;
@@ -1838,11 +1839,17 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
  	if (gc_type == FG_GC)
  		sbi->cur_victim_sec = NULL_SEGNO;

-	if (sync)
-		goto stop;
+	

-	if (!has_not_enough_free_secs(sbi, sec_freed, 0))
+	if (sync || !has_not_enough_free_secs(sbi, sec_freed, 0)) {
+		/*
+		 * f2fs_disable_checkpoint() needs to migrate enough section
+		 * before f2fs_gc() exits.
+		 */
+		if (total_freed < nr_section)
+			goto gc_more;
  		goto stop;
+	}

  	if (skipped_round <= MAX_SKIP_GC_COUNT || skipped_round * 2 < round) {

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 8c17fed8987e..3a3e2cec2ac4 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -524,7 +524,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
  			finish_wait(&sbi->gc_thread->fggc_wq, &wait);
  		} else {
  			f2fs_down_write(&sbi->gc_lock);
-			f2fs_gc(sbi, false, false, false, NULL_SEGNO);
+			f2fs_gc(sbi, false, false, false, NULL_SEGNO, 0);
  		}
  	}
  }
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index d06a577a1208..2f0ad9ffbf17 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2076,7 +2076,7 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)

  	while (!f2fs_time_over(sbi, DISABLE_TIME)) {
  		f2fs_down_write(&sbi->gc_lock);
-		err = f2fs_gc(sbi, true, false, false, NULL_SEGNO);
+		err = f2fs_gc(sbi, true, false, false, NULL_SEGNO, 1);
  		if (err == -ENODATA) {
  			err = 0;
  			break;
-- 
2.32.0

>   		goto stop;
>   
>   	if (skipped_round <= MAX_SKIP_GC_COUNT || skipped_round * 2 < round) {


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