4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Sterba <dsterba@xxxxxxxx>
[ Upstream commit f5194e34cabaddd348a90f950e0a8188dd26cdc0 ]
Prepartory work to fix race between mount and device scan.
The callers will have to manage the critical section, eg. mount wants to
scan and then call btrfs_open_devices without the ioctl scan walking in
and modifying the fs devices in the meantime.
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/super.c | 2 ++
fs/btrfs/volumes.c | 4 ++--
2 files changed, 4 insertions(+), 2 deletions(-)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1565,7 +1565,9 @@ static struct dentry *btrfs_mount_root(s
goto error_fs_info;
}
+ mutex_lock(&uuid_mutex);
error = btrfs_open_devices(fs_devices, mode, fs_type);
+ mutex_unlock(&uuid_mutex);
if (error)
goto error_fs_info;
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1146,7 +1146,8 @@ int btrfs_open_devices(struct btrfs_fs_d
{
int ret;
- mutex_lock(&uuid_mutex);
+ lockdep_assert_held(&uuid_mutex);
+
mutex_lock(&fs_devices->device_list_mutex);
if (fs_devices->opened) {
fs_devices->opened++;
@@ -1156,7 +1157,6 @@ int btrfs_open_devices(struct btrfs_fs_d
ret = open_fs_devices(fs_devices, flags, holder);
}
mutex_unlock(&fs_devices->device_list_mutex);
- mutex_unlock(&uuid_mutex);
return ret;
}
