A few fixes to reduce places where pstore might hang

a system in the crash path. Plus a new mountpoint (/sys/fs/pstore ... makes more sense then /dev/pstore). -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABAgAGBQJRJlSgAAoJEKurIx+X31iBHp4P/iTzfOncyI65UaOkKWlBUzAt bXoiWVAPll15lJuO0Eq4e58c2UEWy9b52MxgCqK38wqSu2Wkd2JLk/q7LFS3gIxb 3h2Lx4CdCCZSENfyGuOTs5WNNcekVFt0qReEXlRAQ6QIGSniO9HT1FklVsqzzDro HUMoGm0/KSWKuq/ls2MD7y/iH3UYbDQ15ED8n1HxWEbpY0+vxCzCMUzNBSOWUsKb HuXeHt06jkvw2DiWuyGBJ10wLHC9c4h37FTdrQFg8YeVBYLZT7boBsnB92Hf12YK 0P782RPiWCIKI23huVHHgS3Rh7hSlKMLLxvrNgIX+XxRMxxjFZyo1xk2NlhUw8ta nGnz7qxqqz+0yCYpF/+0N8ucRH9do64GpCxFXFMTSM9pD4BT7QJAcToswtt3a+Jx EJQF0BNQEZCFwlWLoHZD0znuFFL+jv67RKuiytOXRMgKkxca6RrdIIMeKXF4cl8I z/qPslK0BDfAs2Go+ApMmJ5G4rGziy+IJDLjuxFIBBaKba+79NWDIFA6IV0BquVq idp47OGPTiltb7hOOno+8zRHLQPra7KiWk6Mos2EEb8p+BrrnzspWu1foYEjB4pV AIpC5ClEY+MZHXl30htff9PZgnFm1BOEs6OZmzhLTZevme8KhwdFtrWhY2gH0gvs OM/0NpeTQJzFhS90AbeC =abWF -----END PGP SIGNATURE----- Merge tag 'please-pull-pstore' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux Pull pstore patches from Tony Luck: "A few fixes to reduce places where pstore might hang a system in the crash path. Plus a new mountpoint (/sys/fs/pstore ... makes more sense then /dev/pstore)." Fix up trivial conflict in drivers/firmware/efivars.c * tag 'please-pull-pstore' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux: pstore: Create a convenient mount point for pstore efi_pstore: Introducing workqueue updating sysfs efivars: Disable external interrupt while holding efivars->lock efi_pstore: Avoid deadlock in non-blocking paths pstore: Avoid deadlock in panic and emergency-restart path
2013-02-21 09:38:18 -08:00 · 2013-02-21 09:38:18 -08:00 · 024e4ec185
parent 850cb82b75 fb0af3f2b1
commit 024e4ec185
6 changed files with 191 additions and 59 deletions
--- a/Documentation/ABI/testing/pstore
+++ b/Documentation/ABI/testing/pstore
@ -1,4 +1,4 @@
-Where:		/dev/pstore/...
+Where:		/sys/fs/pstore/... (or /dev/pstore/...)
 Date:		March 2011
 Kernel Version: 2.6.39
 Contact:	tony.luck@intel.com
@ -11,9 +11,9 @@ Description:	Generic interface to platform dependent persistent storage.
 		of the console log is captured, but other interesting
 		data can also be saved.

-		# mount -t pstore -o kmsg_bytes=8000 - /dev/pstore
+		# mount -t pstore -o kmsg_bytes=8000 - /sys/fs/pstore

-		$ ls -l /dev/pstore
+		$ ls -l /sys/fs/pstore/
 		total 0
 		-r--r--r-- 1 root root 7896 Nov 30 15:38 dmesg-erst-1

@ -27,9 +27,9 @@ Description:	Generic interface to platform dependent persistent storage.
 		the file will signal to the underlying persistent storage
 		device that it can reclaim the space for later re-use.

-		$ rm /dev/pstore/dmesg-erst-1
+		$ rm /sys/fs/pstore/dmesg-erst-1

-		The expectation is that all files in /dev/pstore
+		The expectation is that all files in /sys/fs/pstore/
 		will be saved elsewhere and erased from persistent store
 		soon after boot to free up space ready for the next
 		catastrophe.
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@ -158,6 +158,13 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 			  efi_char16_t *variable_name,
 			  efi_guid_t *vendor_guid);

+/*
+ * Prototype for workqueue functions updating sysfs entry
+ */
+
+static void efivar_update_sysfs_entries(struct work_struct *);
+static DECLARE_WORK(efivar_work, efivar_update_sysfs_entries);
+
 /* Return the number of unicode characters in data */
 static unsigned long
 utf16_strnlen(efi_char16_t *s, size_t maxlength)
@ -405,10 +412,11 @@ static efi_status_t
 get_var_data(struct efivars *efivars, struct efi_variable *var)
 {
 	efi_status_t status;
+	unsigned long flags;

-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 	status = get_var_data_locked(efivars, var);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);

 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
@ -537,14 +545,14 @@ efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
 		return -EINVAL;
 	}

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	status = efivars->ops->set_variable(new_var->VariableName,
 					    &new_var->VendorGuid,
 					    new_var->Attributes,
 					    new_var->DataSize,
 					    new_var->Data);

-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
@ -713,7 +721,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 	 * amounts of memory. Pick a default size of 64K if
 	 * QueryVariableInfo() isn't supported by the firmware.
 	 */
-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	if (!efivars->ops->query_variable_info)
 		status = EFI_UNSUPPORTED;
@ -723,7 +731,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 						   &remaining_size, &max_size);
 	}

-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	if (status != EFI_SUCCESS) {
 		if (status != EFI_UNSUPPORTED)
@ -754,7 +762,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 	 * set_variable call, and removal of the variable from the efivars
 	 * list (in the case of an authenticated delete).
 	 */
-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	status = efivars->ops->set_variable(var->var.VariableName,
 					    &var->var.VendorGuid,
@ -762,7 +770,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 					    data);

 	if (status != EFI_SUCCESS) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		kfree(data);

 		return efi_status_to_err(status);
@ -783,21 +791,21 @@ static ssize_t efivarfs_file_write(struct file *file,
 					    NULL);

 	if (status == EFI_BUFFER_TOO_SMALL) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		mutex_lock(&inode->i_mutex);
 		i_size_write(inode, newdatasize + sizeof(attributes));
 		mutex_unlock(&inode->i_mutex);

 	} else if (status == EFI_NOT_FOUND) {
 		list_del(&var->list);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		efivar_unregister(var);
 		drop_nlink(inode);
 		d_delete(file->f_dentry);
 		dput(file->f_dentry);

 	} else {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		pr_warn("efivarfs: inconsistent EFI variable implementation? "
 				"status = %lx\n", status);
 	}
@ -819,11 +827,11 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
 	void *data;
 	ssize_t size = 0;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	status = efivars->ops->get_variable(var->var.VariableName,
 					    &var->var.VendorGuid,
 					    &attributes, &datasize, NULL);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	if (status != EFI_BUFFER_TOO_SMALL)
 		return efi_status_to_err(status);
@ -833,12 +841,12 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
 	if (!data)
 		return -ENOMEM;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	status = efivars->ops->get_variable(var->var.VariableName,
 					    &var->var.VendorGuid,
 					    &attributes, &datasize,
 					    (data + sizeof(attributes)));
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	if (status != EFI_SUCCESS) {
 		size = efi_status_to_err(status);
@ -966,9 +974,9 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
 		goto out;

 	kobject_uevent(&var->kobj, KOBJ_ADD);
-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	list_add(&var->list, &efivars->list);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);
 	d_instantiate(dentry, inode);
 	dget(dentry);
 out:
@ -985,7 +993,7 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 	struct efivars *efivars = var->efivars;
 	efi_status_t status;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	status = efivars->ops->set_variable(var->var.VariableName,
 					    &var->var.VendorGuid,
@ -993,14 +1001,14 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)

 	if (status == EFI_SUCCESS || status == EFI_NOT_FOUND) {
 		list_del(&var->list);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		efivar_unregister(var);
 		drop_nlink(dentry->d_inode);
 		dput(dentry);
 		return 0;
 	}

-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);
 	return -EINVAL;
 };

@ -1066,13 +1074,13 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 		/* copied by the above to local storage in the dentry. */
 		kfree(name);

-		spin_lock(&efivars->lock);
+		spin_lock_irq(&efivars->lock);
 		efivars->ops->get_variable(entry->var.VariableName,
 					   &entry->var.VendorGuid,
 					   &entry->var.Attributes,
 					   &size,
 					   NULL);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);

 		mutex_lock(&inode->i_mutex);
 		inode->i_private = entry;
@ -1123,7 +1131,7 @@ static int efi_pstore_open(struct pstore_info *psi)
 {
 	struct efivars *efivars = psi->data;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	efivars->walk_entry = list_first_entry(&efivars->list,
 					       struct efivar_entry, list);
 	return 0;
@ -1133,7 +1141,7 @@ static int efi_pstore_close(struct pstore_info *psi)
 {
 	struct efivars *efivars = psi->data;

-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);
 	return 0;
 }

@ -1209,8 +1217,18 @@ static int efi_pstore_write(enum pstore_type_id type,
 	int i, ret = 0;
 	u64 storage_space, remaining_space, max_variable_size;
 	efi_status_t status = EFI_NOT_FOUND;
+	unsigned long flags;

-	spin_lock(&efivars->lock);
+	if (pstore_cannot_block_path(reason)) {
+		/*
+		 * If the lock is taken by another cpu in non-blocking path,
+		 * this driver returns without entering firmware to avoid
+		 * hanging up.
+		 */
+		if (!spin_trylock_irqsave(&efivars->lock, flags))
+			return -EBUSY;
+	} else
+		spin_lock_irqsave(&efivars->lock, flags);

 	/*
 	 * Check if there is a space enough to log.
@ -1222,7 +1240,7 @@ static int efi_pstore_write(enum pstore_type_id type,
 						   &remaining_space,
 						   &max_variable_size);
 	if (status || remaining_space < size + DUMP_NAME_LEN * 2) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		*id = part;
 		return -ENOSPC;
 	}
@ -1236,13 +1254,10 @@ static int efi_pstore_write(enum pstore_type_id type,
 	efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
 				   size, psi->buf);

-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);

-	if (size)
-		ret = efivar_create_sysfs_entry(efivars,
-					  utf16_strsize(efi_name,
-							DUMP_NAME_LEN * 2),
-					  efi_name, &vendor);
+	if (reason == KMSG_DUMP_OOPS)
+		schedule_work(&efivar_work);

 	*id = part;
 	return ret;
@ -1263,7 +1278,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 	sprintf(name, "dump-type%u-%u-%d-%lu", type, (unsigned int)id, count,
 		time.tv_sec);

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	for (i = 0; i < DUMP_NAME_LEN; i++)
 		efi_name[i] = name[i];
@ -1307,7 +1322,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 	if (found)
 		list_del(&found->list);

-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	if (found)
 		efivar_unregister(found);
@ -1377,7 +1392,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 		return -EINVAL;
 	}

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	/*
 	 * Does this variable already exist?
@ -1395,7 +1410,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 		}
 	}
 	if (found) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		return -EINVAL;
 	}

@ -1409,10 +1424,10 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
 			status);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		return -EIO;
 	}
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	/* Create the entry in sysfs.  Locking is not required here */
 	status = efivar_create_sysfs_entry(efivars,
@ -1440,7 +1455,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);

 	/*
 	 * Does this variable already exist?
@ -1458,7 +1473,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 		}
 	}
 	if (!found) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		return -EINVAL;
 	}
 	/* force the Attributes/DataSize to 0 to ensure deletion */
@ -1474,18 +1489,87 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
 			status);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		return -EIO;
 	}
 	list_del(&search_efivar->list);
 	/* We need to release this lock before unregistering. */
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);
 	efivar_unregister(search_efivar);

 	/* It's dead Jim.... */
 	return count;
 }

+static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
+{
+	struct efivar_entry *entry, *n;
+	struct efivars *efivars = &__efivars;
+	unsigned long strsize1, strsize2;
+	bool found = false;
+
+	strsize1 = utf16_strsize(variable_name, 1024);
+	list_for_each_entry_safe(entry, n, &efivars->list, list) {
+		strsize2 = utf16_strsize(entry->var.VariableName, 1024);
+		if (strsize1 == strsize2 &&
+			!memcmp(variable_name, &(entry->var.VariableName),
+				strsize2) &&
+			!efi_guidcmp(entry->var.VendorGuid,
+				*vendor)) {
+			found = true;
+			break;
+		}
+	}
+	return found;
+}
+
+static void efivar_update_sysfs_entries(struct work_struct *work)
+{
+	struct efivars *efivars = &__efivars;
+	efi_guid_t vendor;
+	efi_char16_t *variable_name;
+	unsigned long variable_name_size = 1024;
+	efi_status_t status = EFI_NOT_FOUND;
+	bool found;
+
+	/* Add new sysfs entries */
+	while (1) {
+		variable_name = kzalloc(variable_name_size, GFP_KERNEL);
+		if (!variable_name) {
+			pr_err("efivars: Memory allocation failed.\n");
+			return;
+		}
+
+		spin_lock_irq(&efivars->lock);
+		found = false;
+		while (1) {
+			variable_name_size = 1024;
+			status = efivars->ops->get_next_variable(
+							&variable_name_size,
+							variable_name,
+							&vendor);
+			if (status != EFI_SUCCESS) {
+				break;
+			} else {
+				if (!variable_is_present(variable_name,
+				    &vendor)) {
+					found = true;
+					break;
+				}
+			}
+		}
+		spin_unlock_irq(&efivars->lock);
+
+		if (!found) {
+			kfree(variable_name);
+			break;
+		} else
+			efivar_create_sysfs_entry(efivars,
+						  variable_name_size,
+						  variable_name, &vendor);
+	}
+}
+
 /*
 * Let's not leave out systab information that snuck into
 * the efivars driver
@ -1594,9 +1678,9 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 	kfree(short_name);
 	short_name = NULL;

-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	list_add(&new_efivar->list, &efivars->list);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);

 	return 0;
 }
@ -1665,9 +1749,9 @@ void unregister_efivars(struct efivars *efivars)
 	struct efivar_entry *entry, *n;

 	list_for_each_entry_safe(entry, n, &efivars->list, list) {
-		spin_lock(&efivars->lock);
+		spin_lock_irq(&efivars->lock);
 		list_del(&entry->list);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irq(&efivars->lock);
 		efivar_unregister(entry);
 	}
 	if (efivars->new_var)
@ -1823,6 +1907,8 @@ efivars_init(void)
 static void __exit
 efivars_exit(void)
 {
+	cancel_work_sync(&efivar_work);
+
 	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
 		unregister_efivars(&__efivars);
 		kobject_put(efi_kobj);
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@ -418,9 +418,25 @@ static struct file_system_type pstore_fs_type = {
 	.kill_sb	= pstore_kill_sb,
 };

+static struct kobject *pstore_kobj;
+
 static int __init init_pstore_fs(void)
 {
-	return register_filesystem(&pstore_fs_type);
+	int err = 0;
+
+	/* Create a convenient mount point for people to access pstore */
+	pstore_kobj = kobject_create_and_add("pstore", fs_kobj);
+	if (!pstore_kobj) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	err = register_filesystem(&pstore_fs_type);
+	if (err < 0)
+		kobject_put(pstore_kobj);
+
+out:
+	return err;
 }
 module_init(init_pstore_fs)

--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@ -96,6 +96,27 @@ static const char *get_reason_str(enum kmsg_dump_reason reason)
 	}
 }

+bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
+{
+	/*
+	 * In case of NMI path, pstore shouldn't be blocked
+	 * regardless of reason.
+	 */
+	if (in_nmi())
+		return true;
+
+	switch (reason) {
+	/* In panic case, other cpus are stopped by smp_send_stop(). */
+	case KMSG_DUMP_PANIC:
+	/* Emergency restart shouldn't be blocked by spin lock. */
+	case KMSG_DUMP_EMERG:
+		return true;
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(pstore_cannot_block_path);
+
 /*
 * callback from kmsg_dump. (s2,l2) has the most recently
 * written bytes, older bytes are in (s1,l1). Save as much
@ -114,10 +135,12 @@ static void pstore_dump(struct kmsg_dumper *dumper,

 	why = get_reason_str(reason);

-	if (in_nmi()) {
-		is_locked = spin_trylock(&psinfo->buf_lock);
-		if (!is_locked)
-			pr_err("pstore dump routine blocked in NMI, may corrupt error record\n");
+	if (pstore_cannot_block_path(reason)) {
+		is_locked = spin_trylock_irqsave(&psinfo->buf_lock, flags);
+		if (!is_locked) {
+			pr_err("pstore dump routine blocked in %s path, may corrupt error record\n"
+				       , in_nmi() ? "NMI" : why);
+		}
 	} else
 		spin_lock_irqsave(&psinfo->buf_lock, flags);
 	oopscount++;
@ -143,9 +166,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		total += hsize + len;
 		part++;
 	}
-	if (in_nmi()) {
+	if (pstore_cannot_block_path(reason)) {
 		if (is_locked)
-			spin_unlock(&psinfo->buf_lock);
+			spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 	} else
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 }
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@ -740,7 +740,8 @@ struct efivars {
 	 * 1) ->list - adds, removals, reads, writes
 	 * 2) ops.[gs]et_variable() calls.
 	 * It must not be held when creating sysfs entries or calling kmalloc.
-	 * ops.get_next_variable() is only called from register_efivars(),
+	 * ops.get_next_variable() is only called from register_efivars()
+	 * or efivar_update_sysfs_entries(),
 	 * which is protected by the BKL, so that path is safe.
 	 */
 	spinlock_t lock;
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@ -68,12 +68,18 @@ struct pstore_info {

 #ifdef CONFIG_PSTORE
 extern int pstore_register(struct pstore_info *);
+extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
 #else
 static inline int
 pstore_register(struct pstore_info *psi)
 {
 	return -ENODEV;
 }
+static inline bool
+pstore_cannot_block_path(enum kmsg_dump_reason reason)
+{
+	return false;
+}
 #endif

 #endif /*_LINUX_PSTORE_H*/