Btrfs: fix the race between reading and updating devices
On btrfs_congested_fn and __unplug_io_fn paths, we should hold
device_list_mutex to avoid remove/add device path to
update fs_devices->devices
On __btrfs_close_devices and btrfs_prepare_sprout paths, the devices in
fs_devices->devices or fs_devices->devices is updated, so we should hold
the mutex to avoid the reader side to reach them
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 290100f..43c4f09 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -481,6 +481,7 @@
if (--fs_devices->opened > 0)
return 0;
+ mutex_lock(&fs_devices->device_list_mutex);
list_for_each_entry(device, &fs_devices->devices, dev_list) {
if (device->bdev) {
blkdev_put(device->bdev, device->mode);
@@ -495,6 +496,8 @@
device->writeable = 0;
device->in_fs_metadata = 0;
}
+ mutex_unlock(&fs_devices->device_list_mutex);
+
WARN_ON(fs_devices->open_devices);
WARN_ON(fs_devices->rw_devices);
fs_devices->opened = 0;
@@ -1415,7 +1418,11 @@
INIT_LIST_HEAD(&seed_devices->devices);
INIT_LIST_HEAD(&seed_devices->alloc_list);
mutex_init(&seed_devices->device_list_mutex);
+
+ mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
list_splice_init(&fs_devices->devices, &seed_devices->devices);
+ mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
+
list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
list_for_each_entry(device, &seed_devices->devices, dev_list) {
device->fs_devices = seed_devices;