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cmm.c

/*
 *  arch/s390/mm/cmm.c
 *
 *  S390 version
 *    Copyright (C) 2003 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
 *
 *  Collaborative memory management interface.
 */

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.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 <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/diag.h>

static char *sender = "VMRMSVM";
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 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 wait_queue_head_t cmm_thread_wait;
static struct timer_list cmm_timer;

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(addr);
            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_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();
}

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

long
cmm_get_pages(void)
{
      return cmm_pages;
}

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

long
cmm_get_timed_pages(void)
{
      return cmm_timed_pages;
}

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;
}

#ifdef CONFIG_CMM_PROC

static struct ctl_table cmm_table[];

static int
cmm_pages_handler(ctl_table *ctl, int write, struct file *filp,
              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, struct file *filp,
                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,
      },
      { .ctl_name = 0 }
};

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

#ifdef CONFIG_CMM_IUCV
#define SMSG_PREFIX "CMM"
static void
cmm_smsg_target(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_init (void)
{
      int rc = -ENOMEM;

#ifdef CONFIG_CMM_PROC
      cmm_sysctl_header = register_sysctl_table(cmm_dir_table);
      if (!cmm_sysctl_header)
            goto out;
#endif
#ifdef CONFIG_CMM_IUCV
      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;
      init_waitqueue_head(&cmm_thread_wait);
      init_timer(&cmm_timer);
      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_create failed. undo all the stuff from above again.
       */
      unregister_oom_notifier(&cmm_oom_nb);

out_oom_notify:
#ifdef CONFIG_CMM_IUCV
      smsg_unregister_callback(SMSG_PREFIX, cmm_smsg_target);
out_smsg:
#endif
#ifdef CONFIG_CMM_PROC
      unregister_sysctl_table(cmm_sysctl_header);
#endif
out:
      return rc;
}

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

module_init(cmm_init);
module_exit(cmm_exit);

EXPORT_SYMBOL(cmm_set_pages);
EXPORT_SYMBOL(cmm_get_pages);
EXPORT_SYMBOL(cmm_add_timed_pages);
EXPORT_SYMBOL(cmm_get_timed_pages);
EXPORT_SYMBOL(cmm_set_timeout);

MODULE_LICENSE("GPL");

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