efi: pstore: move workqueue handling out of efivars

The worker thread that gets kicked off to sync the state of the
EFI variable list is only used by the EFI pstore implementation,
and is defined in its source file. So let's move its scheduling
there as well. Since our efivar_init() scan will bail on duplicate
entries, there is no need to disable the workqueue like we did
before, so we can run it unconditionally.

Signed-off-by: Ard Biesheuvel <[e-mail]>

drivers/firmware/efi/efi-pstore.c

···
 	 EFI_VARIABLE_RUNTIME_ACCESS)
 
 static LIST_HEAD(efi_pstore_list);
+static DECLARE_WORK(efivar_work, NULL);
 
 static int efi_pstore_open(struct pstore_info *psi)
 {
···
 	ret = efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
 			      preemptible(), record->size, record->psi->buf);
 
-	if (record->reason == KMSG_DUMP_OOPS)
-		efivar_run_worker();
+	if (record->reason == KMSG_DUMP_OOPS && try_module_get(THIS_MODULE))
+		if (!schedule_work(&efivar_work))
+			module_put(THIS_MODULE);
 
 	return ret;
 };
···
 	}
 
 	kfree(entry);
+	module_put(THIS_MODULE);
 }
 
 static __init int efivars_pstore_init(void)

drivers/firmware/efi/vars.c

···
  */
 static DEFINE_SEMAPHORE(efivars_lock);
 
-static bool efivar_wq_enabled = true;
-DECLARE_WORK(efivar_work, NULL);
-EXPORT_SYMBOL_GPL(efivar_work);
-
 static bool
 validate_device_path(efi_char16_t *var_name, int match, u8 *buffer,
 		     unsigned long len)
···
 {
 	size_t i, len8 = len16 / sizeof(efi_char16_t);
 	char *str8;
-
-	/*
-	 * Disable the workqueue since the algorithm it uses for
-	 * detecting new variables won't work with this buggy
-	 * implementation of GetNextVariableName().
-	 */
-	efivar_wq_enabled = false;
 
 	str8 = kzalloc(len8, GFP_KERNEL);
 	if (!str8)
···
 	return __efivars->kobject;
 }
 EXPORT_SYMBOL_GPL(efivars_kobject);
-
-/**
- * efivar_run_worker - schedule the efivar worker thread
- */
-void efivar_run_worker(void)
-{
-	if (efivar_wq_enabled)
-		schedule_work(&efivar_work);
-}
-EXPORT_SYMBOL_GPL(efivar_run_worker);
 
 /**
  * efivars_register - register an efivars

include/linux/efi.h

···
 bool efivar_variable_is_removable(efi_guid_t vendor, const char *name,
 				  size_t len);
 
-extern struct work_struct efivar_work;
-void efivar_run_worker(void);
-
 #if defined(CONFIG_EFI_VARS) || defined(CONFIG_EFI_VARS_MODULE)
 int efivars_sysfs_init(void);