fs/pstore/platform.c - kernel/msm-4.9 - Gitiles

 /*
  * Persistent Storage - platform driver interface parts.
  *
  * Copyright (C) 2007-2008 Google, Inc.
  * 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/console.h>
 #include <linux/module.h>
 #include <linux/pstore.h>
 #include <linux/zlib.h>
 #include <linux/string.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/hardirq.h>
 #include <linux/jiffies.h>
 #include <linux/workqueue.h>

 #include "internal.h"

 /*
  * We defer making "oops" entries appear in pstore - see
  * whether the system is actually still running well enough
  * to let someone see the entry
  */
 static int pstore_update_ms = -1;
 module_param_named(update_ms, pstore_update_ms, int, 0600);
 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
 		 "(default is -1, which means runtime updates are disabled; "
 		 "enabling this option is not safe, it may lead to further "
 		 "corruption on Oopses)");

 static int pstore_new_entry;

 static void pstore_timefunc(unsigned long);
 static DEFINE_TIMER(pstore_timer, pstore_timefunc, 0, 0);

 static void pstore_dowork(struct work_struct *);
 static DECLARE_WORK(pstore_work, pstore_dowork);

 /*
  * pstore_lock just protects "psinfo" during
  * calls to pstore_register()
  */
 static DEFINE_SPINLOCK(pstore_lock);
 struct pstore_info *psinfo;

 static char *backend;

 /* Compression parameters */
 #define COMPR_LEVEL 6
 #define WINDOW_BITS 12
 #define MEM_LEVEL 4
 static struct z_stream_s stream;

 static char *big_oops_buf;
 static size_t big_oops_buf_sz;

 /* How much of the console log to snapshot */
 static unsigned long kmsg_bytes = 10240;

 void pstore_set_kmsg_bytes(int bytes)
 {
 	kmsg_bytes = bytes;
 }

 /* Tag each group of saved records with a sequence number */
 static int	oopscount;

 static const char *get_reason_str(enum kmsg_dump_reason reason)
 {
 	switch (reason) {
 	case KMSG_DUMP_PANIC:
 		return "Panic";
 	case KMSG_DUMP_OOPS:
 		return "Oops";
 	case KMSG_DUMP_EMERG:
 		return "Emergency";
 	case KMSG_DUMP_RESTART:
 		return "Restart";
 	case KMSG_DUMP_HALT:
 		return "Halt";
 	case KMSG_DUMP_POWEROFF:
 		return "Poweroff";
 	default:
 		return "Unknown";
 	}
 }

 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);

 /* Derived from logfs_compress() */
 static int pstore_compress(const void *in, void *out, size_t inlen,
 							size_t outlen)
 {
 	int err, ret;

 	ret = -EIO;
 	err = zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
 						MEM_LEVEL, Z_DEFAULT_STRATEGY);
 	if (err != Z_OK)
 		goto error;

 	stream.next_in = in;
 	stream.avail_in = inlen;
 	stream.total_in = 0;
 	stream.next_out = out;
 	stream.avail_out = outlen;
 	stream.total_out = 0;

 	err = zlib_deflate(&stream, Z_FINISH);
 	if (err != Z_STREAM_END)
 		goto error;

 	err = zlib_deflateEnd(&stream);
 	if (err != Z_OK)
 		goto error;

 	if (stream.total_out >= stream.total_in)
 		goto error;

 	ret = stream.total_out;
 error:
 	return ret;
 }

 /* Derived from logfs_uncompress */
 static int pstore_decompress(void *in, void *out, size_t inlen, size_t outlen)
 {
 	int err, ret;

 	ret = -EIO;
 	err = zlib_inflateInit2(&stream, WINDOW_BITS);
 	if (err != Z_OK)
 		goto error;

 	stream.next_in = in;
 	stream.avail_in = inlen;
 	stream.total_in = 0;
 	stream.next_out = out;
 	stream.avail_out = outlen;
 	stream.total_out = 0;

 	err = zlib_inflate(&stream, Z_FINISH);
 	if (err != Z_STREAM_END)
 		goto error;

 	err = zlib_inflateEnd(&stream);
 	if (err != Z_OK)
 		goto error;

 	ret = stream.total_out;
 error:
 	return ret;
 }

 static void allocate_buf_for_compression(void)
 {
 	size_t size;
 	size_t cmpr;

 	switch (psinfo->bufsize) {
 	/* buffer range for efivars */
 	case 1000 ... 2000:
 		cmpr = 56;
 		break;
 	case 2001 ... 3000:
 		cmpr = 54;
 		break;
 	case 3001 ... 3999:
 		cmpr = 52;
 		break;
 	/* buffer range for nvram, erst */
 	case 4000 ... 10000:
 		cmpr = 45;
 		break;
 	default:
 		cmpr = 60;
 		break;
 	}

 	big_oops_buf_sz = (psinfo->bufsize * 100) / cmpr;
 	big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
 	if (big_oops_buf) {
 		size = max(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
 			zlib_inflate_workspacesize());
 		stream.workspace = kmalloc(size, GFP_KERNEL);
 		if (!stream.workspace) {
 			pr_err("pstore: No memory for compression workspace; "
 				"skipping compression\n");
 			kfree(big_oops_buf);
 			big_oops_buf = NULL;
 		}
 	} else {
 		pr_err("No memory for uncompressed data; "
 			"skipping compression\n");
 		stream.workspace = NULL;
 	}

 }

 /*
  * Called when compression fails, since the printk buffer
  * would be fetched for compression calling it again when
  * compression fails would have moved the iterator of
  * printk buffer which results in fetching old contents.
  * Copy the recent messages from big_oops_buf to psinfo->buf
  */
 static size_t copy_kmsg_to_buffer(int hsize, size_t len)
 {
 	size_t total_len;
 	size_t diff;

 	total_len = hsize + len;

 	if (total_len > psinfo->bufsize) {
 		diff = total_len - psinfo->bufsize + hsize;
 		memcpy(psinfo->buf, big_oops_buf, hsize);
 		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
 					psinfo->bufsize - hsize);
 		total_len = psinfo->bufsize;
 	} else
 		memcpy(psinfo->buf, big_oops_buf, total_len);

 	return total_len;
 }

 /*
  * 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)
 {
 	unsigned long	total = 0;
 	const char	*why;
 	u64		id;
 	unsigned int	part = 1;
 	unsigned long	flags = 0;
 	int		is_locked = 0;
 	int		ret;

 	why = get_reason_str(reason);

 	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++;
 	while (total < kmsg_bytes) {
 		char *dst;
 		unsigned long size;
 		int hsize;
 		int zipped_len = -1;
 		size_t len;
 		bool compressed;
 		size_t total_len;

 		if (big_oops_buf) {
 			dst = big_oops_buf;
 			hsize = sprintf(dst, "%s#%d Part%d\n", why,
 							oopscount, part);
 			size = big_oops_buf_sz - hsize;

 			if (!kmsg_dump_get_buffer(dumper, true, dst + hsize,
 								size, &len))
 				break;

 			zipped_len = pstore_compress(dst, psinfo->buf,
 						hsize + len, psinfo->bufsize);

 			if (zipped_len > 0) {
 				compressed = true;
 				total_len = zipped_len;
 			} else {
 				compressed = false;
 				total_len = copy_kmsg_to_buffer(hsize, len);
 			}
 		} else {
 			dst = psinfo->buf;
 			hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount,
 									part);
 			size = psinfo->bufsize - hsize;
 			dst += hsize;

 			if (!kmsg_dump_get_buffer(dumper, true, dst,
 								size, &len))
 				break;

 			compressed = false;
 			total_len = hsize + len;
 		}

 		ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
 				    oopscount, compressed, total_len, psinfo);
 		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
 			pstore_new_entry = 1;

 		total += total_len;
 		part++;
 	}
 	if (pstore_cannot_block_path(reason)) {
 		if (is_locked)
 			spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 	} else
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 }

 static struct kmsg_dumper pstore_dumper = {
 	.dump = pstore_dump,
 };

 #ifdef CONFIG_PSTORE_CONSOLE
 static void pstore_console_write(struct console *con, const char *s, unsigned c)
 {
 	const char *e = s + c;

 	while (s < e) {
 		unsigned long flags;
 		u64 id;

 		if (c > psinfo->bufsize)
 			c = psinfo->bufsize;

 		if (oops_in_progress) {
 			if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
 				break;
 		} else {
 			spin_lock_irqsave(&psinfo->buf_lock, flags);
 		}
 		memcpy(psinfo->buf, s, c);
 		psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 		s += c;
 		c = e - s;
 	}
 }

 static struct console pstore_console = {
 	.name	= "pstore",
 	.write	= pstore_console_write,
 	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
 	.index	= -1,
 };

 static void pstore_register_console(void)
 {
 	register_console(&pstore_console);
 }
 #else
 static void pstore_register_console(void) {}
 #endif

 static int pstore_write_compat(enum pstore_type_id type,
 			       enum kmsg_dump_reason reason,
 			       u64 *id, unsigned int part, int count,
 			       bool compressed, size_t size,
 			       struct pstore_info *psi)
 {
 	return psi->write_buf(type, reason, id, part, psinfo->buf, compressed,
 			     size, psi);
 }

 /*
  * 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;

 	if (backend && strcmp(backend, psi->name))
 		return -EPERM;

 	spin_lock(&pstore_lock);
 	if (psinfo) {
 		spin_unlock(&pstore_lock);
 		return -EBUSY;
 	}

 	if (!psi->write)
 		psi->write = pstore_write_compat;
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
 	spin_unlock(&pstore_lock);

 	if (owner && !try_module_get(owner)) {
 		psinfo = NULL;
 		return -EINVAL;
 	}

 	allocate_buf_for_compression();

 	if (pstore_is_mounted())
 		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 +
 			msecs_to_jiffies(pstore_update_ms);
 		add_timer(&pstore_timer);
 	}

 	pr_info("pstore: Registered %s as persistent store backend\n",
 		psi->name);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_register);

 /*
  * Read all the records from the persistent store. Create
  * files in our filesystem.  Don't warn about -EEXIST errors
  * when we are re-scanning the backing store looking to add new
  * error records.
  */
 void pstore_get_records(int quiet)
 {
 	struct pstore_info *psi = psinfo;
 	char			*buf = NULL;
 	ssize_t			size;
 	u64			id;
 	int			count;
 	enum pstore_type_id	type;
 	struct timespec		time;
 	int			failed = 0, rc;
 	bool			compressed;
 	int			unzipped_len = -1;

 	if (!psi)
 		return;

 	mutex_lock(&psi->read_mutex);
 	if (psi->open && psi->open(psi))
 		goto out;

 	while ((size = psi->read(&id, &type, &count, &time, &buf, &compressed,
 				psi)) > 0) {
 		if (compressed && (type == PSTORE_TYPE_DMESG)) {
 			if (big_oops_buf)
 				unzipped_len = pstore_decompress(buf,
 							big_oops_buf, size,
 							big_oops_buf_sz);

 			if (unzipped_len > 0) {
 				kfree(buf);
 				buf = big_oops_buf;
 				size = unzipped_len;
 				compressed = false;
 			} else {
 				pr_err("pstore: decompression failed;"
 					"returned %d\n", unzipped_len);
 				compressed = true;
 			}
 		}
 		rc = pstore_mkfile(type, psi->name, id, count, buf,
 				  compressed, (size_t)size, time, psi);
 		if (unzipped_len < 0) {
 			/* Free buffer other than big oops */
 			kfree(buf);
 			buf = NULL;
 		} else
 			unzipped_len = -1;
 		if (rc && (rc != -EEXIST || !quiet))
 			failed++;
 	}
 	if (psi->close)
 		psi->close(psi);
 out:
 	mutex_unlock(&psi->read_mutex);

 	if (failed)
 		printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
 		       failed, psi->name);
 }

 static void pstore_dowork(struct work_struct *work)
 {
 	pstore_get_records(1);
 }

 static void pstore_timefunc(unsigned long dummy)
 {
 	if (pstore_new_entry) {
 		pstore_new_entry = 0;
 		schedule_work(&pstore_work);
 	}

 	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
 }

 module_param(backend, charp, 0444);
 MODULE_PARM_DESC(backend, "Pstore backend to use");
	/*
	* Persistent Storage - platform driver interface parts.
	*
	* Copyright (C) 2007-2008 Google, Inc.
	* 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/console.h>
	#include <linux/module.h>
	#include <linux/pstore.h>
	#include <linux/zlib.h>
	#include <linux/string.h>
	#include <linux/timer.h>
	#include <linux/slab.h>
	#include <linux/uaccess.h>
	#include <linux/hardirq.h>
	#include <linux/jiffies.h>
	#include <linux/workqueue.h>

	#include "internal.h"

	/*
	* We defer making "oops" entries appear in pstore - see
	* whether the system is actually still running well enough
	* to let someone see the entry
	*/
	static int pstore_update_ms = -1;
	module_param_named(update_ms, pstore_update_ms, int, 0600);
	MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
	"(default is -1, which means runtime updates are disabled; "
	"enabling this option is not safe, it may lead to further "
	"corruption on Oopses)");

	static int pstore_new_entry;

	static void pstore_timefunc(unsigned long);
	static DEFINE_TIMER(pstore_timer, pstore_timefunc, 0, 0);

	static void pstore_dowork(struct work_struct *);
	static DECLARE_WORK(pstore_work, pstore_dowork);

	/*
	* pstore_lock just protects "psinfo" during
	* calls to pstore_register()
	*/
	static DEFINE_SPINLOCK(pstore_lock);
	struct pstore_info *psinfo;

	static char *backend;

	/* Compression parameters */
	#define COMPR_LEVEL 6
	#define WINDOW_BITS 12
	#define MEM_LEVEL 4
	static struct z_stream_s stream;

	static char *big_oops_buf;
	static size_t big_oops_buf_sz;

	/* How much of the console log to snapshot */
	static unsigned long kmsg_bytes = 10240;

	void pstore_set_kmsg_bytes(int bytes)
	{
	kmsg_bytes = bytes;
	}

	/* Tag each group of saved records with a sequence number */
	static int oopscount;

	static const char *get_reason_str(enum kmsg_dump_reason reason)
	{
	switch (reason) {
	case KMSG_DUMP_PANIC:
	return "Panic";
	case KMSG_DUMP_OOPS:
	return "Oops";
	case KMSG_DUMP_EMERG:
	return "Emergency";
	case KMSG_DUMP_RESTART:
	return "Restart";
	case KMSG_DUMP_HALT:
	return "Halt";
	case KMSG_DUMP_POWEROFF:
	return "Poweroff";
	default:
	return "Unknown";
	}
	}

	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);

	/* Derived from logfs_compress() */
	static int pstore_compress(const void in, void out, size_t inlen,
	size_t outlen)
	{
	int err, ret;

	ret = -EIO;
	err = zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
	MEM_LEVEL, Z_DEFAULT_STRATEGY);
	if (err != Z_OK)
	goto error;

	stream.next_in = in;
	stream.avail_in = inlen;
	stream.total_in = 0;
	stream.next_out = out;
	stream.avail_out = outlen;
	stream.total_out = 0;

	err = zlib_deflate(&stream, Z_FINISH);
	if (err != Z_STREAM_END)
	goto error;

	err = zlib_deflateEnd(&stream);
	if (err != Z_OK)
	goto error;

	if (stream.total_out >= stream.total_in)
	goto error;

	ret = stream.total_out;
	error:
	return ret;
	}

	/* Derived from logfs_uncompress */
	static int pstore_decompress(void in, void out, size_t inlen, size_t outlen)
	{
	int err, ret;

	ret = -EIO;
	err = zlib_inflateInit2(&stream, WINDOW_BITS);
	if (err != Z_OK)
	goto error;

	stream.next_in = in;
	stream.avail_in = inlen;
	stream.total_in = 0;
	stream.next_out = out;
	stream.avail_out = outlen;
	stream.total_out = 0;

	err = zlib_inflate(&stream, Z_FINISH);
	if (err != Z_STREAM_END)
	goto error;

	err = zlib_inflateEnd(&stream);
	if (err != Z_OK)
	goto error;

	ret = stream.total_out;
	error:
	return ret;
	}

	static void allocate_buf_for_compression(void)
	{
	size_t size;
	size_t cmpr;

	switch (psinfo->bufsize) {
	/* buffer range for efivars */
	case 1000 ... 2000:
	cmpr = 56;
	break;
	case 2001 ... 3000:
	cmpr = 54;
	break;
	case 3001 ... 3999:
	cmpr = 52;
	break;
	/* buffer range for nvram, erst */
	case 4000 ... 10000:
	cmpr = 45;
	break;
	default:
	cmpr = 60;
	break;
	}

	big_oops_buf_sz = (psinfo->bufsize * 100) / cmpr;
	big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
	if (big_oops_buf) {
	size = max(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
	zlib_inflate_workspacesize());
	stream.workspace = kmalloc(size, GFP_KERNEL);
	if (!stream.workspace) {
	pr_err("pstore: No memory for compression workspace; "
	"skipping compression\n");
	kfree(big_oops_buf);
	big_oops_buf = NULL;
	}
	} else {
	pr_err("No memory for uncompressed data; "
	"skipping compression\n");
	stream.workspace = NULL;
	}

	}

	/*
	* Called when compression fails, since the printk buffer
	* would be fetched for compression calling it again when
	* compression fails would have moved the iterator of
	* printk buffer which results in fetching old contents.
	* Copy the recent messages from big_oops_buf to psinfo->buf
	*/
	static size_t copy_kmsg_to_buffer(int hsize, size_t len)
	{
	size_t total_len;
	size_t diff;

	total_len = hsize + len;

	if (total_len > psinfo->bufsize) {
	diff = total_len - psinfo->bufsize + hsize;
	memcpy(psinfo->buf, big_oops_buf, hsize);
	memcpy(psinfo->buf + hsize, big_oops_buf + diff,
	psinfo->bufsize - hsize);
	total_len = psinfo->bufsize;
	} else
	memcpy(psinfo->buf, big_oops_buf, total_len);

	return total_len;
	}

	/*
	* 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)
	{
	unsigned long total = 0;
	const char *why;
	u64 id;
	unsigned int part = 1;
	unsigned long flags = 0;
	int is_locked = 0;
	int ret;

	why = get_reason_str(reason);

	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++;
	while (total < kmsg_bytes) {
	char *dst;
	unsigned long size;
	int hsize;
	int zipped_len = -1;
	size_t len;
	bool compressed;
	size_t total_len;

	if (big_oops_buf) {
	dst = big_oops_buf;
	hsize = sprintf(dst, "%s#%d Part%d\n", why,
	oopscount, part);
	size = big_oops_buf_sz - hsize;

	if (!kmsg_dump_get_buffer(dumper, true, dst + hsize,
	size, &len))
	break;

	zipped_len = pstore_compress(dst, psinfo->buf,
	hsize + len, psinfo->bufsize);

	if (zipped_len > 0) {
	compressed = true;
	total_len = zipped_len;
	} else {
	compressed = false;
	total_len = copy_kmsg_to_buffer(hsize, len);
	}
	} else {
	dst = psinfo->buf;
	hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount,
	part);
	size = psinfo->bufsize - hsize;
	dst += hsize;

	if (!kmsg_dump_get_buffer(dumper, true, dst,
	size, &len))
	break;

	compressed = false;
	total_len = hsize + len;
	}

	ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
	oopscount, compressed, total_len, psinfo);
	if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
	pstore_new_entry = 1;

	total += total_len;
	part++;
	}
	if (pstore_cannot_block_path(reason)) {
	if (is_locked)
	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
	} else
	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
	}

	static struct kmsg_dumper pstore_dumper = {
	.dump = pstore_dump,
	};

	#ifdef CONFIG_PSTORE_CONSOLE
	static void pstore_console_write(struct console con, const char s, unsigned c)
	{
	const char *e = s + c;

	while (s < e) {
	unsigned long flags;
	u64 id;

	if (c > psinfo->bufsize)
	c = psinfo->bufsize;

	if (oops_in_progress) {
	if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
	break;
	} else {
	spin_lock_irqsave(&psinfo->buf_lock, flags);
	}
	memcpy(psinfo->buf, s, c);
	psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
	s += c;
	c = e - s;
	}
	}

	static struct console pstore_console = {
	.name = "pstore",
	.write = pstore_console_write,
	.flags = CON_PRINTBUFFER \| CON_ENABLED \| CON_ANYTIME,
	.index = -1,
	};

	static void pstore_register_console(void)
	{
	register_console(&pstore_console);
	}
	#else
	static void pstore_register_console(void) {}
	#endif

	static int pstore_write_compat(enum pstore_type_id type,
	enum kmsg_dump_reason reason,
	u64 *id, unsigned int part, int count,
	bool compressed, size_t size,
	struct pstore_info *psi)
	{
	return psi->write_buf(type, reason, id, part, psinfo->buf, compressed,
	size, psi);
	}

	/*
	* 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;

	if (backend && strcmp(backend, psi->name))
	return -EPERM;

	spin_lock(&pstore_lock);
	if (psinfo) {
	spin_unlock(&pstore_lock);
	return -EBUSY;
	}

	if (!psi->write)
	psi->write = pstore_write_compat;
	psinfo = psi;
	mutex_init(&psinfo->read_mutex);
	spin_unlock(&pstore_lock);

	if (owner && !try_module_get(owner)) {
	psinfo = NULL;
	return -EINVAL;
	}

	allocate_buf_for_compression();

	if (pstore_is_mounted())
	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 +
	msecs_to_jiffies(pstore_update_ms);
	add_timer(&pstore_timer);
	}

	pr_info("pstore: Registered %s as persistent store backend\n",
	psi->name);

	return 0;
	}
	EXPORT_SYMBOL_GPL(pstore_register);

	/*
	* Read all the records from the persistent store. Create
	* files in our filesystem. Don't warn about -EEXIST errors
	* when we are re-scanning the backing store looking to add new
	* error records.
	*/
	void pstore_get_records(int quiet)
	{
	struct pstore_info *psi = psinfo;
	char *buf = NULL;
	ssize_t size;
	u64 id;
	int count;
	enum pstore_type_id type;
	struct timespec time;
	int failed = 0, rc;
	bool compressed;
	int unzipped_len = -1;

	if (!psi)
	return;

	mutex_lock(&psi->read_mutex);
	if (psi->open && psi->open(psi))
	goto out;

	while ((size = psi->read(&id, &type, &count, &time, &buf, &compressed,
	psi)) > 0) {
	if (compressed && (type == PSTORE_TYPE_DMESG)) {
	if (big_oops_buf)
	unzipped_len = pstore_decompress(buf,
	big_oops_buf, size,
	big_oops_buf_sz);

	if (unzipped_len > 0) {
	kfree(buf);
	buf = big_oops_buf;
	size = unzipped_len;
	compressed = false;
	} else {
	pr_err("pstore: decompression failed;"
	"returned %d\n", unzipped_len);
	compressed = true;
	}
	}
	rc = pstore_mkfile(type, psi->name, id, count, buf,
	compressed, (size_t)size, time, psi);
	if (unzipped_len < 0) {
	/* Free buffer other than big oops */
	kfree(buf);
	buf = NULL;
	} else
	unzipped_len = -1;
	if (rc && (rc != -EEXIST \|\| !quiet))
	failed++;
	}
	if (psi->close)
	psi->close(psi);
	out:
	mutex_unlock(&psi->read_mutex);

	if (failed)
	printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
	failed, psi->name);
	}

	static void pstore_dowork(struct work_struct *work)
	{
	pstore_get_records(1);
	}

	static void pstore_timefunc(unsigned long dummy)
	{
	if (pstore_new_entry) {
	pstore_new_entry = 0;
	schedule_work(&pstore_work);
	}

	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
	}

	module_param(backend, charp, 0444);
	MODULE_PARM_DESC(backend, "Pstore backend to use");