pstore: Don't allow high traffic options on fragile devices

Some pstore backing devices use on board flash as persistent
storage. These have limited numbers of write cycles so it
is a poor idea to use them from high frequency operations.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/acpi/apei/erst.c

@@ -942,6 +942,7 @@ static int erst_clearer(enum pstore_type_id type, u64 id, int count,
 static struct pstore_info erst_info = {
 	.owner		= THIS_MODULE,
 	.name		= "erst",
+	.flags		= PSTORE_FLAGS_FRAGILE,
 	.open		= erst_open_pstore,
 	.close		= erst_close_pstore,
 	.read		= erst_reader,

drivers/firmware/efi/efi-pstore.c

@@ -356,6 +356,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 static struct pstore_info efi_pstore_info = {
 	.owner		= THIS_MODULE,
 	.name		= "efi",
+	.flags		= PSTORE_FLAGS_FRAGILE,
 	.open		= efi_pstore_open,
 	.close		= efi_pstore_close,
 	.read		= efi_pstore_read,

fs/pstore/platform.c

@@ -443,8 +443,11 @@ int pstore_register(struct pstore_info *psi)
 		pstore_get_records(0);
 
 	kmsg_dump_register(&pstore_dumper);
+
+	if ((psi->flags & PSTORE_FLAGS_FRAGILE) == 0) {
 		pstore_register_console();
 		pstore_register_ftrace();
+	}
 
 	if (pstore_update_ms >= 0) {
 		pstore_timer.expires = jiffies +

include/linux/pstore.h

@@ -51,6 +51,7 @@ struct pstore_info {
 	char		*buf;
 	size_t		bufsize;
 	struct mutex	read_mutex;	/* serialize open/read/close */
+	int		flags;
 	int		(*open)(struct pstore_info *psi);
 	int		(*close)(struct pstore_info *psi);
 	ssize_t		(*read)(u64 *id, enum pstore_type_id *type,
@@ -70,6 +71,8 @@ struct pstore_info {
 	void		*data;
 };
 
+#define	PSTORE_FLAGS_FRAGILE	1
+
 #ifdef CONFIG_PSTORE
 extern int pstore_register(struct pstore_info *);
 extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);