[PATCH 01/11] btrfs: initialize sysfs devid and device link for seed device

Anand Jain
2020-08-30T14:42:17Z

The following test case leads to null kobject-being-freed error.

mount seed /mnt
add sprout to /mnt
umount /mnt
mount sprout to /mnt
delete seed

kobject: '(null)' (00000000dd2b87e4): is not initialized, yet kobject_put() is being called.
WARNING: CPU: 1 PID: 15784 at lib/kobject.c:736 kobject_put+0x80/0x350
RIP: 0010:kobject_put+0x80/0x350
::
Call Trace:
btrfs_sysfs_remove_devices_dir+0x6e/0x160 [btrfs]
btrfs_rm_device.cold+0xa8/0x298 [btrfs]
btrfs_ioctl+0x206c/0x22a0 [btrfs]
ksys_ioctl+0xe2/0x140
__x64_sys_ioctl+0x1e/0x29
do_syscall_64+0x96/0x150
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f4047c6288b
::

This is because, at the end of the seed device-delete, we try to remove
the seed's devid sysfs entry. But for the seed devices under the sprout
fs, we don't initialize the devid kobject yet. So this patch initializes
the seed device devid kobject and the device link in the sysfs. This takes
care of the Warning.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
fs/btrfs/sysfs.c | 146 ++++++++++++++++++++++++++++++-----------------
1 file changed, 93 insertions(+), 53 deletions(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 190e59152be5..9b5e58091fae 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1149,45 +1149,48 @@ int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info,
return 0;
}

-/* when one_device is NULL, it removes all device links */
-
-int btrfs_sysfs_remove_devices_dir(struct btrfs_fs_devices *fs_devices,
- struct btrfs_device *one_device)
+static void btrfs_sysfs_remove_device(struct btrfs_device *device)
{
struct hd_struct *disk;
struct kobject *disk_kobj;
+ struct kobject *devices_kobj;

- if (!fs_devices->devices_kobj)
- return -EINVAL;
+ /*
+ * Seed fs_devices devices_kobj aren't used, fetch kobject from the
+ * fs_info::fs_devices.
+ */
+ devices_kobj = device->fs_info->fs_devices->devices_kobj;
+ ASSERT(devices_kobj);

- if (one_device) {
- if (one_device->bdev) {
- disk = one_device->bdev->bd_part;
- disk_kobj = &part_to_dev(disk)->kobj;
- sysfs_remove_link(fs_devices->devices_kobj,
- disk_kobj->name);
- }
+ if (device->bdev) {
+ disk = device->bdev->bd_part;
+ disk_kobj = &part_to_dev(disk)->kobj;
+ sysfs_remove_link(devices_kobj, disk_kobj->name);
+ }

- kobject_del(&one_device->devid_kobj);
- kobject_put(&one_device->devid_kobj);
+ kobject_del(&device->devid_kobj);
+ kobject_put(&device->devid_kobj);

- wait_for_completion(&one_device->kobj_unregister);
+ wait_for_completion(&device->kobj_unregister);
+}

+/* when 2nd argument device is NULL, it removes all devices link */
+int btrfs_sysfs_remove_devices_dir(struct btrfs_fs_devices *fs_devices,
+ struct btrfs_device *device)
+{
+ struct btrfs_fs_devices *seed_fs_devices;
+
+ if (device) {
+ btrfs_sysfs_remove_device(device);
return 0;
}

- list_for_each_entry(one_device, &fs_devices->devices, dev_list) {
-
- if (one_device->bdev) {
- disk = one_device->bdev->bd_part;
- disk_kobj = &part_to_dev(disk)->kobj;
- sysfs_remove_link(fs_devices->devices_kobj,
- disk_kobj->name);
- }
- kobject_del(&one_device->devid_kobj);
- kobject_put(&one_device->devid_kobj);
+ list_for_each_entry(device, &fs_devices->devices, dev_list)
+ btrfs_sysfs_remove_device(device);

- wait_for_completion(&one_device->kobj_unregister);
+ list_for_each_entry(seed_fs_devices, &fs_devices->seed_list, seed_list) {
+ list_for_each_entry(device, &seed_fs_devices->devices, dev_list)
+ btrfs_sysfs_remove_device(device);
}

return 0;
@@ -1271,44 +1274,81 @@ static struct kobj_type devid_ktype = {
.release = btrfs_release_devid_kobj,
};

+static int btrfs_sysfs_add_device(struct btrfs_device *device)
+{
+ int ret;
+ struct kobject *devices_kobj;
+ struct kobject *devinfo_kobj;
+
+ /*
+ * make sure we use the fs_info::fs_devices to fetch the kobjects
+ * even for the seed fs_devices
+ */
+ devices_kobj = device->fs_devices->fs_info->fs_devices->devices_kobj;
+ devinfo_kobj = device->fs_devices->fs_info->fs_devices->devinfo_kobj;
+ ASSERT(devices_kobj);
+ ASSERT(devinfo_kobj);
+
+ if (device->bdev) {
+ struct hd_struct *disk;
+ struct kobject *disk_kobj;
+
+ disk = device->bdev->bd_part;
+ disk_kobj = &part_to_dev(disk)->kobj;
+
+ ret = sysfs_create_link(devices_kobj, disk_kobj,
+ disk_kobj->name);
+ if (ret) {
+ btrfs_warn(device->fs_info,
+ "sysfs create device link failed %d devid %llu",
+ ret, device->devid);
+ return ret;
+ }
+ }
+
+ init_completion(&device->kobj_unregister);
+ ret = kobject_init_and_add(&device->devid_kobj, &devid_ktype,
+ devinfo_kobj, "%llu", device->devid);
+ if (ret) {
+ kobject_put(&device->devid_kobj);
+ btrfs_warn(device->fs_info,
+ "sysfs devinfo init failed %d devid %llu",
+ ret, device->devid);
+ }
+
+ return ret;
+}
+
int btrfs_sysfs_add_devices_dir(struct btrfs_fs_devices *fs_devices,
- struct btrfs_device *one_device)
+ struct btrfs_device *device)
{
- int error = 0;
- struct btrfs_device *dev;
+ int ret = 0;
unsigned int nofs_flag;
+ struct btrfs_fs_devices *seed_fs_devices;

nofs_flag = memalloc_nofs_save();
- list_for_each_entry(dev, &fs_devices->devices, dev_list) {

- if (one_device && one_device != dev)
- continue;
+ if (device)
+ return btrfs_sysfs_add_device(device);

- if (dev->bdev) {
- struct hd_struct *disk;
- struct kobject *disk_kobj;
-
- disk = dev->bdev->bd_part;
- disk_kobj = &part_to_dev(disk)->kobj;
-
- error = sysfs_create_link(fs_devices->devices_kobj,
- disk_kobj, disk_kobj->name);
- if (error)
- break;
- }
+ list_for_each_entry(device, &fs_devices->devices, dev_list) {
+ ret = btrfs_sysfs_add_device(device);
+ if (ret)
+ goto out;
+ }

- init_completion(&dev->kobj_unregister);
- error = kobject_init_and_add(&dev->devid_kobj, &devid_ktype,
- fs_devices->devinfo_kobj, "%llu",
- dev->devid);
- if (error) {
- kobject_put(&dev->devid_kobj);
- break;
+ list_for_each_entry(seed_fs_devices, &fs_devices->seed_list, seed_list) {
+ list_for_each_entry(device, &seed_fs_devices->devices, dev_list) {
+ ret = btrfs_sysfs_add_device(device);
+ if (ret)
+ goto out;
}
}
+
+out:
memalloc_nofs_restore(nofs_flag);

- return error;
+ return ret;
}

void btrfs_kobject_uevent(struct block_device *bdev, enum kobject_action action)
--
2.25.1