Re: [f2fs-dev] [PATCH 1/2] f2fs: check skipped write in f2fs_enable_checkpoint()

Mon, 19 Jan 2026 20:02:50 -0800 

On 1/20/2026 7:47 AM, Zhiguo Niu wrote:

Chao Yu via Linux-f2fs-devel <[email protected]>
于2026年1月19日周一 22:48写道：


This patch introduces sbi->nr_pages[F2FS_SKIPPED_WRITE] to record any
skipped write during data flush in f2fs_enable_checkpoint().

So in the loop of data flush, if there is any skipped write in previous
flush, let's retry sync_inode_sb(), otherwise, all dirty data written
before f2fs_enable_checkpoint() should have been persisted, then break
the retry loop.

Signed-off-by: Chao Yu <[email protected]>
---
Changelog:
- code is based on 'Revert "f2fs: add timeout in f2fs_enable_checkpoint()"'
  fs/f2fs/data.c  | 12 ++++++++++++
  fs/f2fs/f2fs.h  |  2 ++
  fs/f2fs/super.c | 37 +++++++++++++++++++++++++++++++++----
  3 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5b4832956196..00108d5881aa 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3500,6 +3500,15 @@ static inline void account_writeback(struct inode 
*inode, bool inc)
         f2fs_up_read(&F2FS_I(inode)->i_sem);
  }

+static inline void update_skipped_write(struct f2fs_sb_info *sbi,
+                                               struct writeback_control *wbc)
+{
+       long skipped = wbc->pages_skipped;
+
+       if (skipped && is_sbi_flag_set(sbi, SBI_ENABLE_CHECKPOINT))
+               atomic_add(skipped, &sbi->nr_pages[F2FS_SKIPPED_WRITE]);
+}
+
  static int __f2fs_write_data_pages(struct address_space *mapping,
                                                 struct writeback_control *wbc,
                                                 enum iostat_type io_type)
@@ -3564,10 +3573,13 @@ static int __f2fs_write_data_pages(struct address_space 
*mapping,
          */

         f2fs_remove_dirty_inode(inode);
+
+       update_skipped_write(sbi, wbc);

Hi Chao,
Sorry, why do we need to update skipped write here as well?


Zhiguo,

In case we increase pages_skipped in below path:

- __f2fs_write_data_pages
 - f2fs_write_cache_pages
  - f2fs_write_single_data_page
   - folio_redirty_for_writepage
   : wbc->pages_skipped += nr;

Thanks,


thanks!

         return ret;

  skip_write:
         wbc->pages_skipped += get_dirty_pages(inode);
+       update_skipped_write(sbi, wbc);
         trace_f2fs_writepages(mapping->host, wbc, DATA);
         return 0;
  }
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 035239758e33..52cec6b3ecf0 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1238,6 +1238,7 @@ enum count_type {
         F2FS_RD_META,
         F2FS_DIO_WRITE,
         F2FS_DIO_READ,
+       F2FS_SKIPPED_WRITE,     /* skip or fail during f2fs_enable_checkpoint() 
*/
         NR_COUNT_TYPE,
  };

@@ -1476,6 +1477,7 @@ enum {
         SBI_IS_RESIZEFS,                        /* resizefs is in process */
         SBI_IS_FREEZING,                        /* freezefs is in process */
         SBI_IS_WRITABLE,                        /* remove ro mountoption 
transiently */
+       SBI_ENABLE_CHECKPOINT,                  /* indicate it's during 
f2fs_enable_checkpoint() */
         MAX_SBI_FLAG,
  };

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 97c2264ec7fe..0afe9f829058 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2690,6 +2690,7 @@ static int f2fs_enable_checkpoint(struct f2fs_sb_info 
*sbi)
         long long start, writeback, end;
         int ret;
         struct f2fs_lock_context lc;
+       long long skipped_write, dirty_data;

         f2fs_info(sbi, "f2fs_enable_checkpoint() starts, meta: %lld, node: %lld, 
data: %lld",
                                         get_pages(sbi, F2FS_DIRTY_META),
@@ -2698,17 +2699,45 @@ static int f2fs_enable_checkpoint(struct f2fs_sb_info 
*sbi)

         start = ktime_get();

+       set_sbi_flag(sbi, SBI_ENABLE_CHECKPOINT);
+
         /* we should flush all the data to keep data consistency */
         do {
+               skipped_write = get_pages(sbi, F2FS_SKIPPED_WRITE);
+               dirty_data = get_pages(sbi, F2FS_DIRTY_DATA);
+
                 sync_inodes_sb(sbi->sb);
                 f2fs_io_schedule_timeout(DEFAULT_SCHEDULE_TIMEOUT);
-       } while (get_pages(sbi, F2FS_DIRTY_DATA) && retry--);
+
+               f2fs_info(sbi, "sync_inode_sb done, dirty_data: %lld, %lld, "
+                               "skipped write: %lld, %lld, retry: %d",
+                               get_pages(sbi, F2FS_DIRTY_DATA),
+                               dirty_data,
+                               get_pages(sbi, F2FS_SKIPPED_WRITE),
+                               skipped_write, retry);
+
+               /*
+                * sync_inodes_sb() has retry logic, so let's check dirty_data
+                * in prior to skipped_write in case there is no dirty data.
+                */
+               if (!get_pages(sbi, F2FS_DIRTY_DATA))
+                       break;
+               if (get_pages(sbi, F2FS_SKIPPED_WRITE) == skipped_write)
+                       break;
+       } while (retry--);
+
+       clear_sbi_flag(sbi, SBI_ENABLE_CHECKPOINT);

         writeback = ktime_get();

-       if (unlikely(get_pages(sbi, F2FS_DIRTY_DATA)))
-               f2fs_warn(sbi, "checkpoint=enable has some unwritten data: 
%lld",
-                                       get_pages(sbi, F2FS_DIRTY_DATA));
+       if (unlikely(get_pages(sbi, F2FS_DIRTY_DATA) ||
+                       get_pages(sbi, F2FS_SKIPPED_WRITE)))
+               f2fs_warn(sbi, "checkpoint=enable unwritten data: %lld, skipped 
data: %lld, retry: %d",
+                               get_pages(sbi, F2FS_DIRTY_DATA),
+                               get_pages(sbi, F2FS_SKIPPED_WRITE), retry);
+
+       if (get_pages(sbi, F2FS_SKIPPED_WRITE))
+               atomic_set(&sbi->nr_pages[F2FS_SKIPPED_WRITE], 0);

         f2fs_down_write_trace(&sbi->gc_lock, &lc);
         f2fs_dirty_to_prefree(sbi);
--
2.40.1



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