[PATCH] ext4: fix reserved space counter leakage

[Jeffle Xu <jefflexu@linux.alibaba.com>]

When ext4_es_insert_delayed_block() returns error, e.g., ENOMEM,
previously reserved space is not released as the error handling,
in which case @s_dirtyclusters_counter is left over. Since this delayed
extent failes to be inserted into extent status tree, when inode is
written back, the extra @s_dirtyclusters_counter won't be subtracted and
remains there forever.

This can leads to /sys/fs/ext4/<dev>/delayed_allocation_blocks remains
non-zero even when syncfs is executed on the filesystem.

Fixes: 51865fda28e5 ("ext4: let ext4 maintain extent status tree")
Cc: <stable@vger.kernel.org>
Reported-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
 fs/ext4/inode.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 82087657860b..7f15da370281 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1650,6 +1650,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	int ret;
 	bool allocated = false;
+	bool reserved = false;
 
 	/*
 	 * If the cluster containing lblk is shared with a delayed,
@@ -1666,6 +1667,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
 		ret = ext4_da_reserve_space(inode);
 		if (ret != 0)   /* ENOSPC */
 			goto errout;
+		reserved = true;
 	} else {   /* bigalloc */
 		if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk)) {
 			if (!ext4_es_scan_clu(inode,
@@ -1678,6 +1680,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
 					ret = ext4_da_reserve_space(inode);
 					if (ret != 0)   /* ENOSPC */
 						goto errout;
+					reserved = true;
 				} else {
 					allocated = true;
 				}
@@ -1688,6 +1691,8 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
 	}
 
 	ret = ext4_es_insert_delayed_block(inode, lblk, allocated);
+	if (ret && reserved)
+		ext4_da_release_space(inode, 1);
 
 errout:
 	return ret;
-- 
2.27.0