ext4: Add debug message to notify user space is out of free

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7CBCS
CVE: NA

--------------------------------

Add debug message to notify user that ext4_writepages is stuck in loop
caused by ENOSPC.
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>

fs/ext4/inode.c

@@ -2742,6 +2742,9 @@ static int ext4_writepages(struct address_space *mapping,
 	bool done;
 	struct blk_plug plug;
 	bool give_up_on_write = false;
+	unsigned long retry_warn_ddl = 0;
+
+#define RETRY_WARN_TIMEOUT (30 * HZ)
 
 	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 		return -EIO;
@@ -2933,6 +2936,15 @@ static int ext4_writepages(struct address_space *mapping,
 		mpd.io_submit.io_end = NULL;
 
 		if (ret == -ENOSPC && sbi->s_journal) {
+			if (!retry_warn_ddl) {
+				retry_warn_ddl = jiffies + RETRY_WARN_TIMEOUT;
+			} else if (time_after(jiffies, retry_warn_ddl)) {
+				retry_warn_ddl = jiffies + RETRY_WARN_TIMEOUT;
+				ext4_warning(inode->i_sb, "There are no free blocks available for writing pages, total free %llu, pending free %u, please delete big files to free space",
+					ext4_count_free_clusters(inode->i_sb),
+					sbi->s_mb_free_pending);
+			}
+
 			/*
 			 * Commit the transaction which would
 			 * free blocks released in the transaction
@@ -2941,6 +2953,8 @@ static int ext4_writepages(struct address_space *mapping,
 			jbd2_journal_force_commit_nested(sbi->s_journal);
 			ret = 0;
 			continue;
+		} else {
+			retry_warn_ddl = 0;
 		}
 		/* Fatal error - ENOMEM, EIO... */
 		if (ret)