From 5f3164813b90f7dbcb5c3ab9006906222ce471b7 Mon Sep 17 00:00:00 2001
From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Date: Thu, 26 Jun 2014 11:08:16 +0800
Subject: [PATCH] Btrfs: fix race between balance recovery and root deletion
Balance recovery is called when RW mounting or remounting from
RO to RW, it is called to finish roots merging.
When doing balance recovery, relocation root's corresponding
fs root(whose root refs is 0) might be destroyed by cleaner
thread, this will make btrfs fail to mount.
Fix this problem by holding @cleaner_mutex when doing balance
recovery.
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
---
fs/btrfs/disk-io.c | 2 ++
fs/btrfs/super.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f00165de6fbf..08e65e9cf2aa 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2905,7 +2905,9 @@ retry_root_backup:
if (ret)
goto fail_qgroup;
+ mutex_lock(&fs_info->cleaner_mutex);
ret = btrfs_recover_relocation(tree_root);
+ mutex_unlock(&fs_info->cleaner_mutex);
if (ret < 0) {
printk(KERN_WARNING
"BTRFS: failed to recover relocation\n");
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4662d92a4b73..b6ebde231de7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1467,7 +1467,9 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
goto restore;
/* recover relocation */
+ mutex_lock(&fs_info->cleaner_mutex);
ret = btrfs_recover_relocation(root);
+ mutex_unlock(&fs_info->cleaner_mutex);
if (ret)
goto restore;
--
2.34.1