Pull pstore into release branch

drivers/acpi/apei/Kconfig

 config ACPI_APEI
 	bool "ACPI Platform Error Interface (APEI)"
+	select MISC_FILESYSTEMS
 	select PSTORE
 	depends on X86
 	help

drivers/acpi/apei/erst.c

@@ -929,13 +929,17 @@ static int erst_check_table(struct acpi_table_erst *erst_tab)
 	return 0;
 }
 
-static size_t erst_reader(u64 *id, enum pstore_type_id *type,
+static int erst_open_pstore(struct pstore_info *psi);
+static int erst_close_pstore(struct pstore_info *psi);
+static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
 		       struct timespec *time);
 static u64 erst_writer(enum pstore_type_id type, size_t size);
 
 static struct pstore_info erst_info = {
 	.owner		= THIS_MODULE,
 	.name		= "erst",
+	.open		= erst_open_pstore,
+	.close		= erst_close_pstore,
 	.read		= erst_reader,
 	.write		= erst_writer,
 	.erase		= erst_clear
@@ -957,12 +961,32 @@ struct cper_pstore_record {
 	char data[];
 } __packed;
 
-static size_t erst_reader(u64 *id, enum pstore_type_id *type,
+static int reader_pos;
+
+static int erst_open_pstore(struct pstore_info *psi)
+{
+	int rc;
+
+	if (erst_disable)
+		return -ENODEV;
+
+	rc = erst_get_record_id_begin(&reader_pos);
+
+	return rc;
+}
+
+static int erst_close_pstore(struct pstore_info *psi)
+{
+	erst_get_record_id_end();
+
+	return 0;
+}
+
+static ssize_t erst_reader(u64 *id, enum pstore_type_id *type,
 		       struct timespec *time)
 {
 	int rc;
-	ssize_t len;
-	unsigned long flags;
+	ssize_t len = 0;
 	u64 record_id;
 	struct cper_pstore_record *rcd = (struct cper_pstore_record *)
 					(erst_info.buf - sizeof(*rcd));
@@ -970,24 +994,28 @@ static size_t erst_reader(u64 *id, enum pstore_type_id *type,
 	if (erst_disable)
 		return -ENODEV;
 
-	raw_spin_lock_irqsave(&erst_lock, flags);
 skip:
-	rc = __erst_get_next_record_id(&record_id);
-	if (rc) {
-		raw_spin_unlock_irqrestore(&erst_lock, flags);
-		return rc;
-	}
+	rc = erst_get_record_id_next(&reader_pos, &record_id);
+	if (rc)
+		goto out;
+
 	/* no more record */
 	if (record_id == APEI_ERST_INVALID_RECORD_ID) {
-		raw_spin_unlock_irqrestore(&erst_lock, flags);
-		return 0;
+		rc = -1;
+		goto out;
 	}
 
-	len = __erst_read(record_id, &rcd->hdr, sizeof(*rcd) +
-			  erst_erange.size);
+	len = erst_read(record_id, &rcd->hdr, sizeof(*rcd) +
+			erst_info.bufsize);
+	/* The record may be cleared by others, try read next record */
+	if (len == -ENOENT)
+		goto skip;
+	else if (len < 0) {
+		rc = -1;
+		goto out;
+	}
 	if (uuid_le_cmp(rcd->hdr.creator_id, CPER_CREATOR_PSTORE) != 0)
 		goto skip;
-	raw_spin_unlock_irqrestore(&erst_lock, flags);
 
 	*id = record_id;
 	if (uuid_le_cmp(rcd->sec_hdr.section_type,
@@ -1005,7 +1033,8 @@ static size_t erst_reader(u64 *id, enum pstore_type_id *type,
 		time->tv_sec = 0;
 	time->tv_nsec = 0;
 
-	return len - sizeof(*rcd);
+out:
+	return (rc < 0) ? rc : (len - sizeof(*rcd));
 }
 
 static u64 erst_writer(enum pstore_type_id type, size_t size)

fs/pstore/platform.c

@@ -152,21 +152,27 @@ EXPORT_SYMBOL_GPL(pstore_register);
 void pstore_get_records(void)
 {
 	struct pstore_info *psi = psinfo;
-	size_t			size;
+	ssize_t			size;
 	u64			id;
 	enum pstore_type_id	type;
 	struct timespec		time;
-	int			failed = 0;
+	int			failed = 0, rc;
 
 	if (!psi)
 		return;
 
 	mutex_lock(&psinfo->buf_mutex);
+	rc = psi->open(psi);
+	if (rc)
+		goto out;
+
 	while ((size = psi->read(&id, &type, &time)) > 0) {
-		if (pstore_mkfile(type, psi->name, id, psi->buf, size,
+		if (pstore_mkfile(type, psi->name, id, psi->buf, (size_t)size,
 				  time, psi->erase))
 			failed++;
 	}
+	psi->close(psi);
+out:
 	mutex_unlock(&psinfo->buf_mutex);
 
 	if (failed)

include/linux/pstore.h

@@ -35,7 +35,9 @@ struct pstore_info {
 	struct mutex	buf_mutex;	/* serialize access to 'buf' */
 	char		*buf;
 	size_t		bufsize;
-	size_t		(*read)(u64 *id, enum pstore_type_id *type,
+	int		(*open)(struct pstore_info *psi);
+	int		(*close)(struct pstore_info *psi);
+	ssize_t		(*read)(u64 *id, enum pstore_type_id *type,
 			struct timespec *time);
 	u64		(*write)(enum pstore_type_id type, size_t size);
 	int		(*erase)(u64 id);