/*
 *  linux/mm/swapfile.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 */

#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/sched.h>
#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/swap.h>
#include <linux/fs.h>
#include <linux/swapctl.h>
#include <linux/malloc.h>
#include <linux/blkdev.h> /* for blk_size */
#include <linux/vmalloc.h>
#include <linux/dcache.h>

#include <asm/dma.h>
#include <asm/system.h> /* for cli()/sti() */
#include <asm/uaccess.h> /* for copy_to/from_user */
#include <asm/bitops.h>
#include <asm/pgtable.h>

unsigned int nr_swapfiles = 0;

static struct {
        int head;       /* head of priority-ordered swapfile list */
        int next;       /* swapfile to be used next */
} swap_list = {-1, -1};

struct swap_info_struct swap_info[MAX_SWAPFILES];


static inline int scan_swap_map(struct swap_info_struct *si)
{
        unsigned long offset;
        /* 
         * We try to cluster swap pages by allocating them
         * sequentially in swap.  Once we've allocated
         * SWAP_CLUSTER_MAX pages this way, however, we resort to
         * first-free allocation, starting a new cluster.  This
         * prevents us from scattering swap pages all over the entire
         * swap partition, so that we reduce overall disk seek times
         * between swap pages.  -- sct */
        if (si->cluster_nr) {
                while (si->cluster_next <= si->highest_bit) {
                        offset = si->cluster_next++;
                        if (si->swap_map[offset])
                                continue;
                        if (test_bit(offset, si->swap_lockmap))
                                continue;
                        si->cluster_nr--;
                        goto got_page;
                }
        }
        si->cluster_nr = SWAP_CLUSTER_MAX;
        for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
                if (si->swap_map[offset])
                        continue;
                if (test_bit(offset, si->swap_lockmap))
                        continue;
                si->lowest_bit = offset;
got_page:
                si->swap_map[offset] = 1;
                nr_swap_pages--;
                if (offset == si->highest_bit)
                        si->highest_bit--;
                si->cluster_next = offset;
                return offset;
        }
        return 0;
}

unsigned long get_swap_page(void)
{
        struct swap_info_struct * p;
        unsigned long offset, entry;
        int type, wrapped = 0;

        type = swap_list.next;
        if (type < 0)
                return 0;
        if (nr_swap_pages == 0)
                return 0;

        while (1) {
                p = &swap_info[type];
                if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
                        offset = scan_swap_map(p);
                        if (offset) {
                                entry = SWP_ENTRY(type,offset);
                                type = swap_info[type].next;
                                if (type < 0 ||
                                        p->prio != swap_info[type].prio) 
                                {
                                                swap_list.next = swap_list.head;
                                }
                                else
                                {
                                        swap_list.next = type;
                                }
                                return entry;
                        }
                }
                type = p->next;
                if (!wrapped) {
                        if (type < 0 || p->prio != swap_info[type].prio) {
                                type = swap_list.head;
                                wrapped = 1;
                        }
                } else if (type < 0) {
                        return 0;       /* out of swap space */
                }
        }
}

void swap_free(unsigned long entry)
{
        struct swap_info_struct * p;
        unsigned long offset, type;

        if (!entry)
                return;
        type = SWP_TYPE(entry);
        if (type & SHM_SWP_TYPE)
                return;
        if (type >= nr_swapfiles) {
                printk("Trying to free nonexistent swap-page\n");
                return;
        }
        p = & swap_info[type];
        offset = SWP_OFFSET(entry);
        if (offset >= p->max) {
                printk("swap_free: weirdness\n");
                return;
        }
        if (!(p->flags & SWP_USED)) {
                printk("Trying to free swap from unused swap-device\n");
                return;
        }
        if (offset < p->lowest_bit)
                p->lowest_bit = offset;
        if (offset > p->highest_bit)
                p->highest_bit = offset;
        if (!p->swap_map[offset])
                printk("swap_free: swap-space map bad (entry %08lx)\n",entry);
        else
                if (!--p->swap_map[offset])
                        nr_swap_pages++;
        if (p->prio > swap_info[swap_list.next].prio) {
            swap_list.next = swap_list.head;
        }
}

/*
 * Trying to stop swapping from a file is fraught with races, so
 * we repeat quite a bit here when we have to pause. swapoff()
 * isn't exactly timing-critical, so who cares (but this is /really/
 * inefficient, ugh).
 *
 * We return 1 after having slept, which makes the process start over
 * from the beginning for this process..
 */
static inline int unuse_pte(struct vm_area_struct * vma, unsigned long address,
        pte_t *dir, unsigned long entry, unsigned long page)
{
        pte_t pte = *dir;

        if (pte_none(pte))
                return 0;
        if (pte_present(pte)) {
                struct page *pg;
                unsigned long page_nr = MAP_NR(pte_page(pte));
                unsigned long pg_swap_entry;

                if (page_nr >= max_mapnr)
                        return 0;
                pg = mem_map + page_nr;
                if (!(pg_swap_entry = in_swap_cache(pg)))
                        return 0;
                if (SWP_TYPE(pg_swap_entry) != SWP_TYPE(entry))
                        return 0;
                delete_from_swap_cache(pg);
                set_pte(dir, pte_mkdirty(pte));
                if (pg_swap_entry != entry)
                        return 0;
                free_page(page);
                return 1;
        }
        if (pte_val(pte) != entry)
                return 0;
        set_pte(dir, pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot))));
        flush_tlb_page(vma, address);
        ++vma->vm_mm->rss;
        swap_free(pte_val(pte));
        return 1;
}

static inline int unuse_pmd(struct vm_area_struct * vma, pmd_t *dir,
        unsigned long address, unsigned long size, unsigned long offset,
        unsigned long entry, unsigned long page)
{
        pte_t * pte;
        unsigned long end;

        if (pmd_none(*dir))
                return 0;
        if (pmd_bad(*dir)) {
                printk("unuse_pmd: bad pmd (%08lx)\n", pmd_val(*dir));
                pmd_clear(dir);
                return 0;
        }
        pte = pte_offset(dir, address);
        offset += address & PMD_MASK;
        address &= ~PMD_MASK;
        end = address + size;
        if (end > PMD_SIZE)
                end = PMD_SIZE;
        do {
                if (unuse_pte(vma, offset+address-vma->vm_start, pte, entry, 
                                page))
                        return 1;
                address += PAGE_SIZE;
                pte++;
        } while (address < end);
        return 0;
}

static inline int unuse_pgd(struct vm_area_struct * vma, pgd_t *dir,
        unsigned long address, unsigned long size,
        unsigned long entry, unsigned long page)
{
        pmd_t * pmd;
        unsigned long offset, end;

        if (pgd_none(*dir))
                return 0;
        if (pgd_bad(*dir)) {
                printk("unuse_pgd: bad pgd (%08lx)\n", pgd_val(*dir));
                pgd_clear(dir);
                return 0;
        }
        pmd = pmd_offset(dir, address);
        offset = address & PGDIR_MASK;
        address &= ~PGDIR_MASK;
        end = address + size;
        if (end > PGDIR_SIZE)
                end = PGDIR_SIZE;
        do {
                if (unuse_pmd(vma, pmd, address, end - address, offset, entry,
                                 page))
                        return 1;
                address = (address + PMD_SIZE) & PMD_MASK;
                pmd++;
        } while (address < end);
        return 0;
}

static int unuse_vma(struct vm_area_struct * vma, pgd_t *pgdir,
                        unsigned long entry, unsigned long page)
{
        unsigned long start = vma->vm_start, end = vma->vm_end;

        while (start < end) {
                if (unuse_pgd(vma, pgdir, start, end - start, entry, page))
                        return 1;
                start = (start + PGDIR_SIZE) & PGDIR_MASK;
                pgdir++;
        }
        return 0;
}

static int unuse_process(struct mm_struct * mm, unsigned long entry, 
                        unsigned long page)
{
        struct vm_area_struct* vma;

        /*
         * Go through process' page directory.
         */
        if (!mm || mm == &init_mm)
                return 0;
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
                pgd_t * pgd = pgd_offset(mm, vma->vm_start);
                if (unuse_vma(vma, pgd, entry, page))
                        return 1;
        }
        return 0;
}

static unsigned long find_swap_entry(int type)
{
        struct swap_info_struct * p = &swap_info[type];
        int i;

        for (i = 1 ; i < p->max ; i++) {
                if (p->swap_map[i] > 0 && p->swap_map[i] != 0x80)
                        return SWP_ENTRY(type, i);
        }
        return 0;
}

/*
 * We completely avoid races by reading each swap page in advance,
 * and then search for the process using it.  All the necessary
 * page table adjustments can then be made atomically.
 */
static int try_to_unuse(unsigned int type)
{
        unsigned long page = 0;
        struct task_struct *p;
        unsigned long entry;

        /*
         * Find all swap entries in use ...
         */
        while ((entry = find_swap_entry(type)) != 0) {
                if (!page) {
                        page = __get_free_page(GFP_KERNEL);
                        if (!page)
                                return -ENOMEM;
                }

                /*
                 * Read in the page, and then free the swap page.
                 */
                read_swap_page(entry, (char *) page);

                read_lock(&tasklist_lock);
                for_each_task(p) {
                        if (unuse_process(p->mm, entry, page)) {
                                page = 0;
                                goto unlock;
                        }
                }
        unlock:
                read_unlock(&tasklist_lock);
                if (page) {
                        printk("try_to_unuse: didn't find entry %8lx\n",
                                entry);
                        swap_free(entry);
                }
        }

        if (page)
                free_page(page);
        return 0;
}

asmlinkage int sys_swapoff(const char * specialfile)
{
        struct swap_info_struct * p = NULL;
        struct dentry * dentry;
        struct file filp;
        int i, type, prev;
        int err = -EPERM;

        lock_kernel();
        if (!suser())
                goto out;

        dentry = namei(specialfile);
        err = PTR_ERR(dentry);
        if (IS_ERR(dentry))
                goto out;

        prev = -1;
        for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
                p = swap_info + type;
                if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
                        if (p->swap_file) {
                                if (p->swap_file == dentry)
                                  break;
                        } else {
                                if (S_ISBLK(dentry->d_inode->i_mode)
                                    && (p->swap_device == dentry->d_inode->i_rdev))
                                  break;
                        }
                }
                prev = type;
        }
        err = -EINVAL;
        if (type < 0){
                dput(dentry);
                goto out;
        }
        if (prev < 0) {
                swap_list.head = p->next;
        } else {
                swap_info[prev].next = p->next;
        }
        if (type == swap_list.next) {
                /* just pick something that's safe... */
                swap_list.next = swap_list.head;
        }
        p->flags = SWP_USED;
        err = try_to_unuse(type);
        if (err) {
                dput(dentry);
                /* re-insert swap space back into swap_list */
                for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
                        if (p->prio >= swap_info[i].prio)
                                break;
                p->next = i;
                if (prev < 0)
                        swap_list.head = swap_list.next = p - swap_info;
                else
                        swap_info[prev].next = p - swap_info;
                p->flags = SWP_WRITEOK;
                goto out;
        }
        if(p->swap_device){
                memset(&filp, 0, sizeof(filp));         
                filp.f_dentry = dentry;
                filp.f_mode = 3; /* read write */
                /* open it again to get fops */
                if( !blkdev_open(dentry->d_inode, &filp) &&
                   filp.f_op && filp.f_op->release){
                        filp.f_op->release(dentry->d_inode,&filp);
                        filp.f_op->release(dentry->d_inode,&filp);
                }
        }
        dput(dentry);

        nr_swap_pages -= p->pages;
        dput(p->swap_file);
        p->swap_file = NULL;
        p->swap_device = 0;
        vfree(p->swap_map);
        p->swap_map = NULL;
        free_page((long) p->swap_lockmap);
        p->swap_lockmap = NULL;
        p->flags = 0;
        err = 0;
out:
        unlock_kernel();
        return err;
}

int get_swaparea_info(char *buf)
{
        char * page = (char *) __get_free_page(GFP_KERNEL);
        struct swap_info_struct *ptr = swap_info;
        int i, j, len = 0, usedswap;

        if (!page)
                return -ENOMEM;

        len += sprintf(buf, "Filename\t\t\tType\t\tSize\tUsed\tPriority\n");
        for (i = 0 ; i < nr_swapfiles ; i++, ptr++) {
                if (ptr->flags & SWP_USED) {
                        char * path = d_path(ptr->swap_file, page, PAGE_SIZE);

                        len += sprintf(buf + len, "%-31s ", path);

                        if (!ptr->swap_device)
                                len += sprintf(buf + len, "file\t\t");
                        else
                                len += sprintf(buf + len, "partition\t");

                        usedswap = 0;
                        for (j = 0; j < ptr->max; ++j)
                                switch (ptr->swap_map[j]) {
                                        case 128:
                                        case 0:
                                                continue;
                                        default:
                                                usedswap++;
                                }
                        len += sprintf(buf + len, "%d\t%d\t%d\n", ptr->pages << (PAGE_SHIFT - 10), 
                                usedswap << (PAGE_SHIFT - 10), ptr->prio);
                }
        }
        free_page((unsigned long) page);
        return len;
}

/*
 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
 *
 * The swapon system call
 */
asmlinkage int sys_swapon(const char * specialfile, int swap_flags)
{
        struct swap_info_struct * p;
        struct dentry * swap_dentry;
        unsigned int type;
        int i, j, prev;
        int error = -EPERM;
        struct file filp;
        static int least_priority = 0;

        lock_kernel();
        if (!suser())
                goto out;
        memset(&filp, 0, sizeof(filp));
        p = swap_info;
        for (type = 0 ; type < nr_swapfiles ; type++,p++)
                if (!(p->flags & SWP_USED))
                        break;
        if (type >= MAX_SWAPFILES)
                goto out;
        if (type >= nr_swapfiles)
                nr_swapfiles = type+1;
        p->flags = SWP_USED;
        p->swap_file = NULL;
        p->swap_device = 0;
        p->swap_map = NULL;
        p->swap_lockmap = NULL;
        p->lowest_bit = 0;
        p->highest_bit = 0;
        p->cluster_nr = 0;
        p->max = 1;
        p->next = -1;
        if (swap_flags & SWAP_FLAG_PREFER) {
                p->prio =
                  (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
        } else {
                p->prio = --least_priority;
        }
        swap_dentry = namei(specialfile);
        error = PTR_ERR(swap_dentry);
        if (IS_ERR(swap_dentry))
                goto bad_swap_2;

        p->swap_file = swap_dentry;
        error = -EINVAL;

        if (S_ISBLK(swap_dentry->d_inode->i_mode)) {
                p->swap_device = swap_dentry->d_inode->i_rdev;
                set_blocksize(p->swap_device, PAGE_SIZE);
                
                filp.f_dentry = swap_dentry;
                filp.f_mode = 3; /* read write */
                error = blkdev_open(swap_dentry->d_inode, &filp);
                if (error)
                        goto bad_swap_2;
                error = -ENODEV;
                if (!p->swap_device ||
                    (blk_size[MAJOR(p->swap_device)] &&
                     !blk_size[MAJOR(p->swap_device)][MINOR(p->swap_device)]))
                        goto bad_swap;
                error = -EBUSY;
                for (i = 0 ; i < nr_swapfiles ; i++) {
                        if (i == type)
                                continue;
                        if (p->swap_device == swap_info[i].swap_device)
                                goto bad_swap;
                }
        } else if (!S_ISREG(swap_dentry->d_inode->i_mode))
                goto bad_swap;
        p->swap_lockmap = (unsigned char *) get_free_page(GFP_USER);
        if (!p->swap_lockmap) {
                printk("Unable to start swapping: out of memory :-)\n");
                error = -ENOMEM;
                goto bad_swap;
        }
        read_swap_page(SWP_ENTRY(type,0), (char *) p->swap_lockmap);
        if (memcmp("SWAP-SPACE",p->swap_lockmap+PAGE_SIZE-10,10)) {
                printk("Unable to find swap-space signature\n");
                error = -EINVAL;
                goto bad_swap;
        }
        memset(p->swap_lockmap+PAGE_SIZE-10,0,10);
        j = 0;
        p->lowest_bit = 0;
        p->highest_bit = 0;
        for (i = 1 ; i < 8*PAGE_SIZE ; i++) {
                if (test_bit(i,p->swap_lockmap)) {
                        if (!p->lowest_bit)
                                p->lowest_bit = i;
                        p->highest_bit = i;
                        p->max = i+1;
                        j++;
                }
        }
        if (!j) {
                printk("Empty swap-file\n");
                error = -EINVAL;
                goto bad_swap;
        }
        p->swap_map = (unsigned char *) vmalloc(p->max);
        if (!p->swap_map) {
                error = -ENOMEM;
                goto bad_swap;
        }
        for (i = 1 ; i < p->max ; i++) {
                if (test_bit(i,p->swap_lockmap))
                        p->swap_map[i] = 0;
                else
                        p->swap_map[i] = 0x80;
        }
        p->swap_map[0] = 0x80;
        memset(p->swap_lockmap,0,PAGE_SIZE);
        p->flags = SWP_WRITEOK;
        p->pages = j;
        nr_swap_pages += j;
        printk("Adding Swap: %dk swap-space (priority %d)\n",
               j<<(PAGE_SHIFT-10), p->prio);

        /* insert swap space into swap_list: */
        prev = -1;
        for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
                if (p->prio >= swap_info[i].prio) {
                        break;
                }
                prev = i;
        }
        p->next = i;
        if (prev < 0) {
                swap_list.head = swap_list.next = p - swap_info;
        } else {
                swap_info[prev].next = p - swap_info;
        }
        error = 0;
        goto out;
bad_swap:
        if(filp.f_op && filp.f_op->release)
                filp.f_op->release(filp.f_dentry->d_inode,&filp);
bad_swap_2:
        free_page((long) p->swap_lockmap);
        vfree(p->swap_map);
        dput(p->swap_file);
        p->swap_device = 0;
        p->swap_file = NULL;
        p->swap_map = NULL;
        p->swap_lockmap = NULL;
        p->flags = 0;
out:
        unlock_kernel();
        return error;
}

void si_swapinfo(struct sysinfo *val)
{
        unsigned int i, j;

        val->freeswap = val->totalswap = 0;
        for (i = 0; i < nr_swapfiles; i++) {
                if ((swap_info[i].flags & SWP_WRITEOK) != SWP_WRITEOK)
                        continue;
                for (j = 0; j < swap_info[i].max; ++j)
                        switch (swap_info[i].swap_map[j]) {
                                case 128:
                                        continue;
                                case 0:
                                        ++val->freeswap;
                                default:
                                        ++val->totalswap;
                        }
        }
        val->freeswap <<= PAGE_SHIFT;
        val->totalswap <<= PAGE_SHIFT;
        return;
}