f2fs: fix fsck inconsistency caused by incorrect nat_entry flag usage

f2fs_need_dentry_mark() reads nat_entry flags without mutual exclusion
with the checkpoint path, which can result in an incorrect inode block
marking state. The scenario is as follows:

create & write & fsync 'file A'                 write checkpoint
- f2fs_do_sync_file // inline inode
 - f2fs_write_inode // inode folio is dirty
                                                - f2fs_write_checkpoint
                                                 - f2fs_flush_merged_writes
                                                 - f2fs_sync_node_pages
 - f2fs_fsync_node_pages // no dirty node
 - f2fs_need_inode_block_update // return true
 - f2fs_fsync_node_pages // inode dirtied
  - f2fs_need_dentry_mark //return true
                                                 - f2fs_flush_nat_entries
                                                - f2fs_write_checkpoint end
  - __write_node_folio // inode with DENT_BIT_SHIFT set
  SPO, "fsck --dry-run" find inode has already checkpointed but still
  with DENT_BIT_SHIFT set

The state observed by f2fs_need_dentry_mark() can differ from the state
observed in __write_node_folio() after acquiring sbi->node_write. The
root cause is that the semantics of IS_CHECKPOINTED and
HAS_FSYNCED_INODE are only guaranteed after the checkpoint write has
fully completed.

This patch moves set_dentry_mark() into __write_node_folio() and
protects it with the sbi->node_write lock.

Cc: stable@kernel.org
Fixes: 88bd02c ("f2fs: fix conditions to remain recovery information in f2fs_sync_file")
Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Yongpeng Yang

fs/f2fs/node.c

@@ -1799,13 +1799,12 @@ static bool __write_node_folio(struct folio *folio, bool atomic, bool *submitted
 		goto redirty_out;
 	}
 
-	if (atomic) {
-		if (!test_opt(sbi, NOBARRIER))
-			fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
-		if (IS_INODE(folio))
-			set_dentry_mark(folio,
+	if (atomic && !test_opt(sbi, NOBARRIER))
+		fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
+
+	if (IS_INODE(folio) && (atomic || is_fsync_dnode(folio)))
+		set_dentry_mark(folio,
 				f2fs_need_dentry_mark(sbi, ino_of_node(folio)));
-	}
 
 	/* should add to global list before clearing PAGECACHE status */
 	if (f2fs_in_warm_node_list(folio)) {
@@ -1956,9 +1955,6 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
 					if (is_inode_flag_set(inode,
 								FI_DIRTY_INODE))
 						f2fs_update_inode(inode, folio);
-					if (!atomic)
-						set_dentry_mark(folio,
-							f2fs_need_dentry_mark(sbi, ino));
 				}
 				/* may be written by other thread */
 				if (!folio_test_dirty(folio))