Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[cris-mirror.git] / fs / pstore / platform.c

/*
 * 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
 */

#define pr_fmt(fmt) "pstore: " fmt

#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>
#ifdef CONFIG_PSTORE_ZLIB_COMPRESS
#include <linux/zlib.h>
#endif
#ifdef CONFIG_PSTORE_LZO_COMPRESS
#include <linux/lzo.h>
#endif
#ifdef CONFIG_PSTORE_LZ4_COMPRESS
#include <linux/lz4.h>
#endif
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/uaccess.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(struct timer_list *);
static DEFINE_TIMER(pstore_timer, pstore_timefunc);

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 */
#ifdef CONFIG_PSTORE_ZLIB_COMPRESS
#define COMPR_LEVEL 6
#define WINDOW_BITS 12
#define MEM_LEVEL 4
static struct z_stream_s stream;
#else
static unsigned char *workspace;
#endif

struct pstore_zbackend {
        int (*compress)(const void *in, void *out, size_t inlen, size_t outlen);
        int (*decompress)(void *in, void *out, size_t inlen, size_t outlen);
        void (*allocate)(void);
        void (*free)(void);

        const char *name;
};

static char *big_oops_buf;
static size_t big_oops_buf_sz;

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

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);

#ifdef CONFIG_PSTORE_ZLIB_COMPRESS
/* Derived from logfs_compress() */
static int compress_zlib(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 decompress_zlib(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_zlib(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("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;
        }

}

static void free_zlib(void)
{
        kfree(stream.workspace);
        stream.workspace = NULL;
        kfree(big_oops_buf);
        big_oops_buf = NULL;
        big_oops_buf_sz = 0;
}

static const struct pstore_zbackend backend_zlib = {
        .compress       = compress_zlib,
        .decompress     = decompress_zlib,
        .allocate       = allocate_zlib,
        .free           = free_zlib,
        .name           = "zlib",
};
#endif

#ifdef CONFIG_PSTORE_LZO_COMPRESS
static int compress_lzo(const void *in, void *out, size_t inlen, size_t outlen)
{
        int ret;

        ret = lzo1x_1_compress(in, inlen, out, &outlen, workspace);
        if (ret != LZO_E_OK) {
                pr_err("lzo_compress error, ret = %d!\n", ret);
                return -EIO;
        }

        return outlen;
}

static int decompress_lzo(void *in, void *out, size_t inlen, size_t outlen)
{
        int ret;

        ret = lzo1x_decompress_safe(in, inlen, out, &outlen);
        if (ret != LZO_E_OK) {
                pr_err("lzo_decompress error, ret = %d!\n", ret);
                return -EIO;
        }

        return outlen;
}

static void allocate_lzo(void)
{
        big_oops_buf_sz = lzo1x_worst_compress(psinfo->bufsize);
        big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
        if (big_oops_buf) {
                workspace = kmalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
                if (!workspace) {
                        pr_err("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");
                workspace = NULL;
        }
}

static void free_lzo(void)
{
        kfree(workspace);
        kfree(big_oops_buf);
        big_oops_buf = NULL;
        big_oops_buf_sz = 0;
}

static const struct pstore_zbackend backend_lzo = {
        .compress       = compress_lzo,
        .decompress     = decompress_lzo,
        .allocate       = allocate_lzo,
        .free           = free_lzo,
        .name           = "lzo",
};
#endif

#ifdef CONFIG_PSTORE_LZ4_COMPRESS
static int compress_lz4(const void *in, void *out, size_t inlen, size_t outlen)
{
        int ret;

        ret = LZ4_compress_default(in, out, inlen, outlen, workspace);
        if (!ret) {
                pr_err("LZ4_compress_default error; compression failed!\n");
                return -EIO;
        }

        return ret;
}

static int decompress_lz4(void *in, void *out, size_t inlen, size_t outlen)
{
        int ret;

        ret = LZ4_decompress_safe(in, out, inlen, outlen);
        if (ret < 0) {
                /*
                 * LZ4_decompress_safe will return an error code
                 * (< 0) if decompression failed
                 */
                pr_err("LZ4_decompress_safe error, ret = %d!\n", ret);
                return -EIO;
        }

        return ret;
}

static void allocate_lz4(void)
{
        big_oops_buf_sz = LZ4_compressBound(psinfo->bufsize);
        big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
        if (big_oops_buf) {
                workspace = kmalloc(LZ4_MEM_COMPRESS, GFP_KERNEL);
                if (!workspace) {
                        pr_err("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");
                workspace = NULL;
        }
}

static void free_lz4(void)
{
        kfree(workspace);
        kfree(big_oops_buf);
        big_oops_buf = NULL;
        big_oops_buf_sz = 0;
}

static const struct pstore_zbackend backend_lz4 = {
        .compress       = compress_lz4,
        .decompress     = decompress_lz4,
        .allocate       = allocate_lz4,
        .free           = free_lz4,
        .name           = "lz4",
};
#endif

static const struct pstore_zbackend *zbackend =
#if defined(CONFIG_PSTORE_ZLIB_COMPRESS)
        &backend_zlib;
#elif defined(CONFIG_PSTORE_LZO_COMPRESS)
        &backend_lzo;
#elif defined(CONFIG_PSTORE_LZ4_COMPRESS)
        &backend_lz4;
#else
        NULL;
#endif

static int pstore_compress(const void *in, void *out,
                           size_t inlen, size_t outlen)
{
        if (zbackend)
                return zbackend->compress(in, out, inlen, outlen);
        else
                return -EIO;
}

static int pstore_decompress(void *in, void *out, size_t inlen, size_t outlen)
{
        if (zbackend)
                return zbackend->decompress(in, out, inlen, outlen);
        else
                return -EIO;
}

static void allocate_buf_for_compression(void)
{
        if (zbackend) {
                pr_info("using %s compression\n", zbackend->name);
                zbackend->allocate();
        } else {
                pr_err("allocate compression buffer error!\n");
        }
}

static void free_buf_for_compression(void)
{
        if (zbackend)
                zbackend->free();
        else
                pr_err("free compression buffer error!\n");
}

/*
 * 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;
}

void pstore_record_init(struct pstore_record *record,
                        struct pstore_info *psinfo)
{
        memset(record, 0, sizeof(*record));

        record->psi = psinfo;

        /* Report zeroed timestamp if called before timekeeping has resumed. */
        record->time = ns_to_timespec(ktime_get_real_fast_ns());
}

/*
 * 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;
        unsigned int    part = 1;
        unsigned long   flags = 0;
        int             is_locked;
        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);
                        return;
                }
        } else {
                spin_lock_irqsave(&psinfo->buf_lock, flags);
                is_locked = 1;
        }
        oopscount++;
        while (total < kmsg_bytes) {
                char *dst;
                size_t dst_size;
                int header_size;
                int zipped_len = -1;
                size_t dump_size;
                struct pstore_record record;

                pstore_record_init(&record, psinfo);
                record.type = PSTORE_TYPE_DMESG;
                record.count = oopscount;
                record.reason = reason;
                record.part = part;
                record.buf = psinfo->buf;

                if (big_oops_buf && is_locked) {
                        dst = big_oops_buf;
                        dst_size = big_oops_buf_sz;
                } else {
                        dst = psinfo->buf;
                        dst_size = psinfo->bufsize;
                }

                /* Write dump header. */
                header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
                                 oopscount, part);
                dst_size -= header_size;

                /* Write dump contents. */
                if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
                                          dst_size, &dump_size))
                        break;

                if (big_oops_buf && is_locked) {
                        zipped_len = pstore_compress(dst, psinfo->buf,
                                                header_size + dump_size,
                                                psinfo->bufsize);

                        if (zipped_len > 0) {
                                record.compressed = true;
                                record.size = zipped_len;
                        } else {
                                record.size = copy_kmsg_to_buffer(header_size,
                                                                  dump_size);
                        }
                } else {
                        record.size = header_size + dump_size;
                }

                ret = psinfo->write(&record);
                if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
                        pstore_new_entry = 1;

                total += record.size;
                part++;
        }
        if (is_locked)
                spin_unlock_irqrestore(&psinfo->buf_lock, flags);
}

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

/*
 * Register with kmsg_dump to save last part of console log on panic.
 */
static void pstore_register_kmsg(void)
{
        kmsg_dump_register(&pstore_dumper);
}

static void pstore_unregister_kmsg(void)
{
        kmsg_dump_unregister(&pstore_dumper);
}

#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) {
                struct pstore_record record;
                unsigned long flags;

                pstore_record_init(&record, psinfo);
                record.type = PSTORE_TYPE_CONSOLE;

                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);
                }
                record.buf = (char *)s;
                record.size = c;
                psinfo->write(&record);
                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);
}

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

static int pstore_write_user_compat(struct pstore_record *record,
                                    const char __user *buf)
{
        int ret = 0;

        if (record->buf)
                return -EINVAL;

        record->buf = memdup_user(buf, record->size);
        if (IS_ERR(record->buf)) {
                ret = PTR_ERR(record->buf);
                goto out;
        }

        ret = record->psi->write(record);

        kfree(record->buf);
out:
        record->buf = NULL;

        return unlikely(ret < 0) ? ret : record->size;
}

/*
 * 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.
 */
int pstore_register(struct pstore_info *psi)
{
        struct module *owner = psi->owner;

        if (backend && strcmp(backend, psi->name)) {
                pr_warn("ignoring unexpected backend '%s'\n", psi->name);
                return -EPERM;
        }

        /* Sanity check flags. */
        if (!psi->flags) {
                pr_warn("backend '%s' must support at least one frontend\n",
                        psi->name);
                return -EINVAL;
        }

        /* Check for required functions. */
        if (!psi->read || !psi->write) {
                pr_warn("backend '%s' must implement read() and write()\n",
                        psi->name);
                return -EINVAL;
        }

        spin_lock(&pstore_lock);
        if (psinfo) {
                pr_warn("backend '%s' already loaded: ignoring '%s'\n",
                        psinfo->name, psi->name);
                spin_unlock(&pstore_lock);
                return -EBUSY;
        }

        if (!psi->write_user)
                psi->write_user = pstore_write_user_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);

        if (psi->flags & PSTORE_FLAGS_DMESG)
                pstore_register_kmsg();
        if (psi->flags & PSTORE_FLAGS_CONSOLE)
                pstore_register_console();
        if (psi->flags & PSTORE_FLAGS_FTRACE)
                pstore_register_ftrace();
        if (psi->flags & PSTORE_FLAGS_PMSG)
                pstore_register_pmsg();

        /* Start watching for new records, if desired. */
        if (pstore_update_ms >= 0) {
                pstore_timer.expires = jiffies +
                        msecs_to_jiffies(pstore_update_ms);
                add_timer(&pstore_timer);
        }

        /*
         * Update the module parameter backend, so it is visible
         * through /sys/module/pstore/parameters/backend
         */
        backend = psi->name;

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

        module_put(owner);

        return 0;
}
EXPORT_SYMBOL_GPL(pstore_register);

void pstore_unregister(struct pstore_info *psi)
{
        /* Stop timer and make sure all work has finished. */
        pstore_update_ms = -1;
        del_timer_sync(&pstore_timer);
        flush_work(&pstore_work);

        if (psi->flags & PSTORE_FLAGS_PMSG)
                pstore_unregister_pmsg();
        if (psi->flags & PSTORE_FLAGS_FTRACE)
                pstore_unregister_ftrace();
        if (psi->flags & PSTORE_FLAGS_CONSOLE)
                pstore_unregister_console();
        if (psi->flags & PSTORE_FLAGS_DMESG)
                pstore_unregister_kmsg();

        free_buf_for_compression();

        psinfo = NULL;
        backend = NULL;
}
EXPORT_SYMBOL_GPL(pstore_unregister);

static void decompress_record(struct pstore_record *record)
{
        int unzipped_len;
        char *decompressed;

        if (!record->compressed)
                return;

        /* Only PSTORE_TYPE_DMESG support compression. */
        if (record->type != PSTORE_TYPE_DMESG) {
                pr_warn("ignored compressed record type %d\n", record->type);
                return;
        }

        /* No compression method has created the common buffer. */
        if (!big_oops_buf) {
                pr_warn("no decompression buffer allocated\n");
                return;
        }

        unzipped_len = pstore_decompress(record->buf, big_oops_buf,
                                         record->size, big_oops_buf_sz);
        if (unzipped_len <= 0) {
                pr_err("decompression failed: %d\n", unzipped_len);
                return;
        }

        /* Build new buffer for decompressed contents. */
        decompressed = kmalloc(unzipped_len + record->ecc_notice_size,
                               GFP_KERNEL);
        if (!decompressed) {
                pr_err("decompression ran out of memory\n");
                return;
        }
        memcpy(decompressed, big_oops_buf, unzipped_len);

        /* Append ECC notice to decompressed buffer. */
        memcpy(decompressed + unzipped_len, record->buf + record->size,
               record->ecc_notice_size);

        /* Swap out compresed contents with decompressed contents. */
        kfree(record->buf);
        record->buf = decompressed;
        record->size = unzipped_len;
        record->compressed = false;
}

/*
 * Read all the records from one persistent store backend. 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_backend_records(struct pstore_info *psi,
                                struct dentry *root, int quiet)
{
        int failed = 0;
        unsigned int stop_loop = 65536;

        if (!psi || !root)
                return;

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

        /*
         * Backend callback read() allocates record.buf. decompress_record()
         * may reallocate record.buf. On success, pstore_mkfile() will keep
         * the record.buf, so free it only on failure.
         */
        for (; stop_loop; stop_loop--) {
                struct pstore_record *record;
                int rc;

                record = kzalloc(sizeof(*record), GFP_KERNEL);
                if (!record) {
                        pr_err("out of memory creating record\n");
                        break;
                }
                pstore_record_init(record, psi);

                record->size = psi->read(record);

                /* No more records left in backend? */
                if (record->size <= 0) {
                        kfree(record);
                        break;
                }

                decompress_record(record);
                rc = pstore_mkfile(root, record);
                if (rc) {
                        /* pstore_mkfile() did not take record, so free it. */
                        kfree(record->buf);
                        kfree(record);
                        if (rc != -EEXIST || !quiet)
                                failed++;
                }
        }
        if (psi->close)
                psi->close(psi);
out:
        mutex_unlock(&psi->read_mutex);

        if (failed)
                pr_warn("failed to create %d record(s) from '%s'\n",
                        failed, psi->name);
        if (!stop_loop)
                pr_err("looping? Too many records seen from '%s'\n",
                        psi->name);
}

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

static void pstore_timefunc(struct timer_list *unused)
{
        if (pstore_new_entry) {
                pstore_new_entry = 0;
                schedule_work(&pstore_work);
        }

        if (pstore_update_ms >= 0)
                mod_timer(&pstore_timer,
                          jiffies + msecs_to_jiffies(pstore_update_ms));
}

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