pstore: new filesystem interface to platform persistent storage

Some platforms have a small amount of non-volatile storage that
can be used to store information useful to diagnose the cause of
a system crash.  This is the generic part of a file system interface
that presents information from the crash as a series of files in
/dev/pstore.  Once the information has been seen, the underlying
storage is freed by deleting the files.

Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 202 insertions, 0 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
new file mode 100644
index 0000000..705fdf8
--- /dev/null
+++ b/fs/pstore/platform.c
@@ -0,0 +1,202 @@
+/*
+ * Persistent Storage - platform driver interface parts.
+ *
+ * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/atomic.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kmsg_dump.h>
+#include <linux/module.h>
+#include <linux/pstore.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+/*
+ * pstore_lock just protects "psinfo" during
+ * calls to pstore_register()
+ */
+static DEFINE_SPINLOCK(pstore_lock);
+static struct pstore_info *psinfo;
+
+/* How much of the console log to snapshot. /sys/fs/pstore/kmsg_bytes */
+static unsigned long kmsg_bytes = 10240;
+
+static ssize_t b_show(struct kobject *kobj,
+		      struct kobj_attribute *attr, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%lu\n", kmsg_bytes);
+}
+
+static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
+		       const char *buf, size_t count)
+{
+	return (sscanf(buf, "%lu", &kmsg_bytes) > 0) ? count : 0;
+}
+
+struct kobj_attribute pstore_kmsg_bytes_attr =
+	__ATTR(kmsg_bytes, S_IRUGO | S_IWUSR, b_show, b_store);
+
+/* Tag each group of saved records with a sequence number */
+static int	oopscount;
+
+/*
+ * callback from kmsg_dump. (s2,l2) has the most recently
+ * written bytes, older bytes are in (s1,l1). Save as much
+ * as we can from the end of the buffer.
+ */
+static void pstore_dump(struct kmsg_dumper *dumper,
+	    enum kmsg_dump_reason reason,
+	    const char *s1, unsigned long l1,
+	    const char *s2, unsigned long l2)
+{
+	unsigned long	s1_start, s2_start;
+	unsigned long	l1_cpy, l2_cpy;
+	unsigned long	size, total = 0;
+	char		*dst;
+	u64		id;
+	int		hsize, part = 1;
+
+	mutex_lock(&psinfo->buf_mutex);
+	oopscount++;
+	while (total < kmsg_bytes) {
+		dst = psinfo->buf;
+		hsize = sprintf(dst, "Oops#%d Part%d\n", oopscount, part++);
+		size = psinfo->bufsize - hsize;
+		dst += hsize;
+
+		l2_cpy = min(l2, size);
+		l1_cpy = min(l1, size - l2_cpy);
+
+		if (l1_cpy + l2_cpy == 0)
+			break;
+
+		s2_start = l2 - l2_cpy;
+		s1_start = l1 - l1_cpy;
+
+		memcpy(dst, s1 + s1_start, l1_cpy);
+		memcpy(dst + l1_cpy, s2 + s2_start, l2_cpy);
+
+		id = psinfo->write(PSTORE_TYPE_DMESG, hsize + l1_cpy + l2_cpy);
+		if (pstore_is_mounted())
+			pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id,
+				      psinfo->buf, hsize + l1_cpy + l2_cpy,
+				      CURRENT_TIME, psinfo->erase);
+		l1 -= l1_cpy;
+		l2 -= l2_cpy;
+		total += l1_cpy + l2_cpy;
+	}
+	mutex_unlock(&psinfo->buf_mutex);
+}
+
+static struct kmsg_dumper pstore_dumper = {
+	.dump = pstore_dump,
+};
+
+/*
+ * platform specific persistent storage driver registers with
+ * us here. If pstore is already mounted, call the platform
+ * read function right away to populate the file system. If not
+ * then the pstore mount code will call us later to fill out
+ * the file system.
+ *
+ * Register with kmsg_dump to save last part of console log on panic.
+ */
+int pstore_register(struct pstore_info *psi)
+{
+	struct module *owner = psi->owner;
+
+	spin_lock(&pstore_lock);
+	if (psinfo) {
+		spin_unlock(&pstore_lock);
+		return -EBUSY;
+	}
+	psinfo = psi;
+	spin_unlock(&pstore_lock);
+
+	if (owner && !try_module_get(owner)) {
+		psinfo = NULL;
+		return -EINVAL;
+	}
+
+	if (pstore_is_mounted())
+		pstore_get_records();
+
+	kmsg_dump_register(&pstore_dumper);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pstore_register);
+
+/*
+ * Read all the records from the persistent store. Create and
+ * file files in our filesystem.
+ */
+void pstore_get_records(void)
+{
+	struct pstore_info *psi = psinfo;
+	size_t			size;
+	u64			id;
+	enum pstore_type_id	type;
+	struct timespec		time;
+	int			failed = 0;
+
+	if (!psi)
+		return;
+
+	mutex_lock(&psinfo->buf_mutex);
+	while ((size = psi->read(&id, &type, &time)) > 0) {
+		if (pstore_mkfile(type, psi->name, id, psi->buf, size,
+				  time, psi->erase))
+			failed++;
+	}
+	mutex_unlock(&psinfo->buf_mutex);
+
+	if (failed)
+		printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
+		       failed, psi->name);
+}
+
+/*
+ * Call platform driver to write a record to the
+ * persistent store.
+ */
+int pstore_write(enum pstore_type_id type, char *buf, size_t size)
+{
+	u64	id;
+
+	if (!psinfo)
+		return -ENODEV;
+
+	if (size > psinfo->bufsize)
+		return -EFBIG;
+
+	mutex_lock(&psinfo->buf_mutex);
+	memcpy(psinfo->buf, buf, size);
+	id = psinfo->write(type, size);
+	if (pstore_is_mounted())
+		pstore_mkfile(PSTORE_TYPE_DMESG, psinfo->name, id, psinfo->buf,
+			      size, CURRENT_TIME, psinfo->erase);
+	mutex_unlock(&psinfo->buf_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pstore_write);