cmm.c

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/*
 *  Collaborative memory management interface.
 *
 *    Copyright IBM Corp 2003, 2010
 *    Author(s): Martin Schwidefsky <[email protected]>,
 *
 */

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/sched.h>
#include <linux/sysctl.h>
#include <linux/ctype.h>
#include <linux/swap.h>
#include <linux/kthread.h>
#include <linux/oom.h>
#include <linux/suspend.h>
#include <linux/uaccess.h>

#include <asm/pgalloc.h>
#include <asm/diag.h>

#ifdef CONFIG_CMM_IUCV
static char *cmm_default_sender = "VMRMSVM";
#endif
static char *sender;
module_param(sender, charp, 0400);
MODULE_PARM_DESC(sender,
         "Guest name that may send SMSG messages (default VMRMSVM)");

#include "../../../drivers/s390/net/smsgiucv.h"

#define CMM_NR_PAGES ((PAGE_SIZE / sizeof(unsigned long)) - 2)

struct cmm_page_array {
    struct cmm_page_array *next;
    unsigned long index;
    unsigned long pages[CMM_NR_PAGES];
};

static long cmm_pages;
static long cmm_timed_pages;
static volatile long cmm_pages_target;
static volatile long cmm_timed_pages_target;
static long cmm_timeout_pages;
static long cmm_timeout_seconds;
static int cmm_suspended;

static struct cmm_page_array *cmm_page_list;
static struct cmm_page_array *cmm_timed_page_list;
static DEFINE_SPINLOCK(cmm_lock);

static struct task_struct *cmm_thread_ptr;
static DECLARE_WAIT_QUEUE_HEAD(cmm_thread_wait);
static DEFINE_TIMER(cmm_timer, NULL, 0, 0);

static void cmm_timer_fn(unsigned long);
static void cmm_set_timer(void);

static long cmm_alloc_pages(long nr, long *counter,
                struct cmm_page_array **list)
{
    struct cmm_page_array *pa, *npa;
    unsigned long addr;

    while (nr) {
        addr = __get_free_page(GFP_NOIO);
        if (!addr)
            break;
        spin_lock(&cmm_lock);
        pa = *list;
        if (!pa || pa->index >= CMM_NR_PAGES) {
            /* Need a new page for the page list. */
            spin_unlock(&cmm_lock);
            npa = (struct cmm_page_array *)
                __get_free_page(GFP_NOIO);
            if (!npa) {
                free_page(addr);
                break;
            }
            spin_lock(&cmm_lock);
            pa = *list;
            if (!pa || pa->index >= CMM_NR_PAGES) {
                npa->next = pa;
                npa->index = 0;
                pa = npa;
                *list = pa;
            } else
                free_page((unsigned long) npa);
        }
        diag10_range(addr >> PAGE_SHIFT, 1);
        pa->pages[pa->index++] = addr;
        (*counter)++;
        spin_unlock(&cmm_lock);
        nr--;
    }
    return nr;
}

static long cmm_free_pages(long nr, long *counter, struct cmm_page_array **list)
{
    struct cmm_page_array *pa;
    unsigned long addr;

    spin_lock(&cmm_lock);
    pa = *list;
    while (nr) {
        if (!pa || pa->index <= 0)
            break;
        addr = pa->pages[--pa->index];
        if (pa->index == 0) {
            pa = pa->next;
            free_page((unsigned long) *list);
            *list = pa;
        }
        free_page(addr);
        (*counter)--;
        nr--;
    }
    spin_unlock(&cmm_lock);
    return nr;
}

static int cmm_oom_notify(struct notifier_block *self,
              unsigned long dummy, void *parm)
{
    unsigned long *freed = parm;
    long nr = 256;

    nr = cmm_free_pages(nr, &cmm_timed_pages, &cmm_timed_page_list);
    if (nr > 0)
        nr = cmm_free_pages(nr, &cmm_pages, &cmm_page_list);
    cmm_pages_target = cmm_pages;
    cmm_timed_pages_target = cmm_timed_pages;
    *freed += 256 - nr;
    return NOTIFY_OK;
}

static struct notifier_block cmm_oom_nb = {
    .notifier_call = cmm_oom_notify,
};

static int cmm_thread(void *dummy)
{
    int rc;

    while (1) {
        rc = wait_event_interruptible(cmm_thread_wait,
            (!cmm_suspended && (cmm_pages != cmm_pages_target ||
             cmm_timed_pages != cmm_timed_pages_target)) ||
             kthread_should_stop());
        if (kthread_should_stop() || rc == -ERESTARTSYS) {
            cmm_pages_target = cmm_pages;
            cmm_timed_pages_target = cmm_timed_pages;
            break;
        }
        if (cmm_pages_target > cmm_pages) {
            if (cmm_alloc_pages(1, &cmm_pages, &cmm_page_list))
                cmm_pages_target = cmm_pages;
        } else if (cmm_pages_target < cmm_pages) {
            cmm_free_pages(1, &cmm_pages, &cmm_page_list);
        }
        if (cmm_timed_pages_target > cmm_timed_pages) {
            if (cmm_alloc_pages(1, &cmm_timed_pages,
                       &cmm_timed_page_list))
                cmm_timed_pages_target = cmm_timed_pages;
        } else if (cmm_timed_pages_target < cmm_timed_pages) {
            cmm_free_pages(1, &cmm_timed_pages,
                       &cmm_timed_page_list);
        }
        if (cmm_timed_pages > 0 && !timer_pending(&cmm_timer))
            cmm_set_timer();
    }
    return 0;
}

static void cmm_kick_thread(void)
{
    wake_up(&cmm_thread_wait);
}

static void cmm_set_timer(void)
{
    if (cmm_timed_pages_target <= 0 || cmm_timeout_seconds <= 0) {
        if (timer_pending(&cmm_timer))
            del_timer(&cmm_timer);
        return;
    }
    if (timer_pending(&cmm_timer)) {
        if (mod_timer(&cmm_timer, jiffies + cmm_timeout_seconds*HZ))
            return;
    }
    cmm_timer.function = cmm_timer_fn;
    cmm_timer.data = 0;
    cmm_timer.expires = jiffies + cmm_timeout_seconds*HZ;
    add_timer(&cmm_timer);
}

static void cmm_timer_fn(unsigned long ignored)
{
    long nr;

    nr = cmm_timed_pages_target - cmm_timeout_pages;
    if (nr < 0)
        cmm_timed_pages_target = 0;
    else
        cmm_timed_pages_target = nr;
    cmm_kick_thread();
    cmm_set_timer();
}

static void cmm_set_pages(long nr)
{
    cmm_pages_target = nr;
    cmm_kick_thread();
}

static long cmm_get_pages(void)
{
    return cmm_pages;
}

static void cmm_add_timed_pages(long nr)
{
    cmm_timed_pages_target += nr;
    cmm_kick_thread();
}

static long cmm_get_timed_pages(void)
{
    return cmm_timed_pages;
}

static void cmm_set_timeout(long nr, long seconds)
{
    cmm_timeout_pages = nr;
    cmm_timeout_seconds = seconds;
    cmm_set_timer();
}

static int cmm_skip_blanks(char *cp, char **endp)
{
    char *str;

    for (str = cp; *str == ' ' || *str == '\t'; str++)
        ;
    *endp = str;
    return str != cp;
}

static struct ctl_table cmm_table[];

static int cmm_pages_handler(ctl_table *ctl, int write, void __user *buffer,
                 size_t *lenp, loff_t *ppos)
{
    char buf[16], *p;
    long nr;
    int len;

    if (!*lenp || (*ppos && !write)) {
        *lenp = 0;
        return 0;
    }

    if (write) {
        len = *lenp;
        if (copy_from_user(buf, buffer,
                   len > sizeof(buf) ? sizeof(buf) : len))
            return -EFAULT;
        buf[sizeof(buf) - 1] = '\0';
        cmm_skip_blanks(buf, &p);
        nr = simple_strtoul(p, &p, 0);
        if (ctl == &cmm_table[0])
            cmm_set_pages(nr);
        else
            cmm_add_timed_pages(nr);
    } else {
        if (ctl == &cmm_table[0])
            nr = cmm_get_pages();
        else
            nr = cmm_get_timed_pages();
        len = sprintf(buf, "%ld\n", nr);
        if (len > *lenp)
            len = *lenp;
        if (copy_to_user(buffer, buf, len))
            return -EFAULT;
    }
    *lenp = len;
    *ppos += len;
    return 0;
}

static int cmm_timeout_handler(ctl_table *ctl, int write,  void __user *buffer,
                   size_t *lenp, loff_t *ppos)
{
    char buf[64], *p;
    long nr, seconds;
    int len;

    if (!*lenp || (*ppos && !write)) {
        *lenp = 0;
        return 0;
    }

    if (write) {
        len = *lenp;
        if (copy_from_user(buf, buffer,
                   len > sizeof(buf) ? sizeof(buf) : len))
            return -EFAULT;
        buf[sizeof(buf) - 1] = '\0';
        cmm_skip_blanks(buf, &p);
        nr = simple_strtoul(p, &p, 0);
        cmm_skip_blanks(p, &p);
        seconds = simple_strtoul(p, &p, 0);
        cmm_set_timeout(nr, seconds);
    } else {
        len = sprintf(buf, "%ld %ld\n",
                  cmm_timeout_pages, cmm_timeout_seconds);
        if (len > *lenp)
            len = *lenp;
        if (copy_to_user(buffer, buf, len))
            return -EFAULT;
    }
    *lenp = len;
    *ppos += len;
    return 0;
}

static struct ctl_table cmm_table[] = {
    {
        .procname   = "cmm_pages",
        .mode       = 0644,
        .proc_handler   = cmm_pages_handler,
    },
    {
        .procname   = "cmm_timed_pages",
        .mode       = 0644,
        .proc_handler   = cmm_pages_handler,
    },
    {
        .procname   = "cmm_timeout",
        .mode       = 0644,
        .proc_handler   = cmm_timeout_handler,
    },
    { }
};

static struct ctl_table cmm_dir_table[] = {
    {
        .procname   = "vm",
        .maxlen     = 0,
        .mode       = 0555,
        .child      = cmm_table,
    },
    { }
};

#ifdef CONFIG_CMM_IUCV
#define SMSG_PREFIX "CMM"
static void cmm_smsg_target(const char *from, char *msg)
{
    long nr, seconds;

    if (strlen(sender) > 0 && strcmp(from, sender) != 0)
        return;
    if (!cmm_skip_blanks(msg + strlen(SMSG_PREFIX), &msg))
        return;
    if (strncmp(msg, "SHRINK", 6) == 0) {
        if (!cmm_skip_blanks(msg + 6, &msg))
            return;
        nr = simple_strtoul(msg, &msg, 0);
        cmm_skip_blanks(msg, &msg);
        if (*msg == '\0')
            cmm_set_pages(nr);
    } else if (strncmp(msg, "RELEASE", 7) == 0) {
        if (!cmm_skip_blanks(msg + 7, &msg))
            return;
        nr = simple_strtoul(msg, &msg, 0);
        cmm_skip_blanks(msg, &msg);
        if (*msg == '\0')
            cmm_add_timed_pages(nr);
    } else if (strncmp(msg, "REUSE", 5) == 0) {
        if (!cmm_skip_blanks(msg + 5, &msg))
            return;
        nr = simple_strtoul(msg, &msg, 0);
        if (!cmm_skip_blanks(msg, &msg))
            return;
        seconds = simple_strtoul(msg, &msg, 0);
        cmm_skip_blanks(msg, &msg);
        if (*msg == '\0')
            cmm_set_timeout(nr, seconds);
    }
}
#endif

static struct ctl_table_header *cmm_sysctl_header;

static int cmm_suspend(void)
{
    cmm_suspended = 1;
    cmm_free_pages(cmm_pages, &cmm_pages, &cmm_page_list);
    cmm_free_pages(cmm_timed_pages, &cmm_timed_pages, &cmm_timed_page_list);
    return 0;
}

static int cmm_resume(void)
{
    cmm_suspended = 0;
    cmm_kick_thread();
    return 0;
}

static int cmm_power_event(struct notifier_block *this,
               unsigned long event, void *ptr)
{
    switch (event) {
    case PM_POST_HIBERNATION:
        return cmm_resume();
    case PM_HIBERNATION_PREPARE:
        return cmm_suspend();
    default:
        return NOTIFY_DONE;
    }
}

static struct notifier_block cmm_power_notifier = {
    .notifier_call = cmm_power_event,
};

static int __init cmm_init(void)
{
    int rc = -ENOMEM;

    cmm_sysctl_header = register_sysctl_table(cmm_dir_table);
    if (!cmm_sysctl_header)
        goto out_sysctl;
#ifdef CONFIG_CMM_IUCV
    /* convert sender to uppercase characters */
    if (sender) {
        int len = strlen(sender);
        while (len--)
            sender[len] = toupper(sender[len]);
    } else {
        sender = cmm_default_sender;
    }

    rc = smsg_register_callback(SMSG_PREFIX, cmm_smsg_target);
    if (rc < 0)
        goto out_smsg;
#endif
    rc = register_oom_notifier(&cmm_oom_nb);
    if (rc < 0)
        goto out_oom_notify;
    rc = register_pm_notifier(&cmm_power_notifier);
    if (rc)
        goto out_pm;
    cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
    rc = IS_ERR(cmm_thread_ptr) ? PTR_ERR(cmm_thread_ptr) : 0;
    if (rc)
        goto out_kthread;
    return 0;

out_kthread:
    unregister_pm_notifier(&cmm_power_notifier);
out_pm:
    unregister_oom_notifier(&cmm_oom_nb);
out_oom_notify:
#ifdef CONFIG_CMM_IUCV
    smsg_unregister_callback(SMSG_PREFIX, cmm_smsg_target);
out_smsg:
#endif
    unregister_sysctl_table(cmm_sysctl_header);
out_sysctl:
    del_timer_sync(&cmm_timer);
    return rc;
}
module_init(cmm_init);

static void __exit cmm_exit(void)
{
    unregister_sysctl_table(cmm_sysctl_header);
#ifdef CONFIG_CMM_IUCV
    smsg_unregister_callback(SMSG_PREFIX, cmm_smsg_target);
#endif
    unregister_pm_notifier(&cmm_power_notifier);
    unregister_oom_notifier(&cmm_oom_nb);
    kthread_stop(cmm_thread_ptr);
    del_timer_sync(&cmm_timer);
    cmm_free_pages(cmm_pages, &cmm_pages, &cmm_page_list);
    cmm_free_pages(cmm_timed_pages, &cmm_timed_pages, &cmm_timed_page_list);
}
module_exit(cmm_exit);

MODULE_LICENSE("GPL");