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

#include <linux/malloc.h>
#include <linux/smp_lock.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapctl.h>
#include <linux/blkdev.h> /* for blk_size */
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/shm.h>

#include <asm/pgtable.h>

unsigned int nr_swapfiles = 0;

struct swap_list_t swap_list = {-1, -1};

struct swap_info_struct swap_info[MAX_SWAPFILES];

#define SWAPFILE_CLUSTER 256

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
         * SWAPFILE_CLUSTER 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 = SWAPFILE_CLUSTER;
        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)
                goto out;

        type = SWP_TYPE(entry);
        if (type & SHM_SWP_TYPE)
                goto out;
        if (type >= nr_swapfiles)
                goto bad_nofile;
        p = & swap_info[type];
        if (!(p->flags & SWP_USED))
                goto bad_device;
        if (p->prio > swap_info[swap_list.next].prio)
                swap_list.next = swap_list.head;
        offset = SWP_OFFSET(entry);
        if (offset >= p->max)
                goto bad_offset;
        if (!p->swap_map[offset])
                goto bad_free;
        if (p->swap_map[offset] < SWAP_MAP_MAX) {
                if (!--p->swap_map[offset])
                {
                        if (offset < p->lowest_bit)
                                p->lowest_bit = offset;
                        if (offset > p->highest_bit)
                                p->highest_bit = offset;
                        nr_swap_pages++;
                }
        }
#ifdef DEBUG_SWAP
        printk("DebugVM: swap_free(entry %08lx, count now %d)\n",
               entry, p->swap_map[offset]);
#endif
out:
        return;

bad_nofile:
        printk("swap_free: Trying to free nonexistent swap-page\n");
        goto out;
bad_device:
        printk("swap_free: Trying to free swap from unused swap-device\n");
        goto out;
bad_offset:
        printk("swap_free: offset exceeds max\n");
        goto out;
bad_free:
        printk("swap_free: swap-space map bad (entry %08lx)\n",entry);
        goto out;
}

/*
 * The swap entry has been read in advance, and we return 1 to indicate
 * that the page has been used or is no longer needed.
 *
 * Always set the resulting pte to be nowrite (the same as COW pages
 * after one process has exited).  We don't know just how many PTEs will
 * share this swap entry, so be cautious and let do_wp_page work out
 * what to do if a write is requested later.
 */
static inline void 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;
        if (pte_present(pte)) {
                /* If this entry is swap-cached, then page must already
                   hold the right address for any copies in physical
                   memory */
                if (pte_page(pte) != page)
                        return;
                /* We will be removing the swap cache in a moment, so... */
                set_pte(dir, pte_mkdirty(pte));
                return;
        }
        if (pte_val(pte) != entry)
                return;
        set_pte(dir, pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
        swap_free(entry);
        atomic_inc(&mem_map[MAP_NR(page)].count);
        ++vma->vm_mm->rss;
}

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

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

static void 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) {
                unuse_pgd(vma, pgdir, start, end - start, entry, page);
                start = (start + PGDIR_SIZE) & PGDIR_MASK;
                pgdir++;
        }
}

static void 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;
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
                pgd_t * pgd = pgd_offset(mm, vma->vm_start);
                unuse_vma(vma, pgd, entry, page);
        }
        return;
}

/*
 * 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)
{
        struct swap_info_struct * si = &swap_info[type];
        struct task_struct *p;
        struct page *page_map;
        unsigned long entry, page;
        int i;

        while (1) {
                /*
                 * Find a swap page in use and read it in.
                 */
                for (i = 1; i < si->max ; i++) {
                        if (si->swap_map[i] > 0 && si->swap_map[i] != SWAP_MAP_BAD) {
                                goto found_entry;
                        }
                }
                break;

        found_entry:
                entry = SWP_ENTRY(type, i);

                /* Get a page for the entry, using the existing swap
                   cache page if there is one.  Otherwise, get a clean
                   page and read the swap into it. */
                page_map = read_swap_cache(entry);
                if (!page_map) {
                        /*
                         * Continue searching if the entry became unused.
                         */
                        if (si->swap_map[i] == 0)
                                continue;
                        return -ENOMEM;
                }
                page = page_address(page_map);
                read_lock(&tasklist_lock);
                for_each_task(p)
                        unuse_process(p->mm, entry, page);
                read_unlock(&tasklist_lock);
                shm_unuse(entry, page);
                /* Now get rid of the extra reference to the temporary
                   page we've been using. */
                if (PageSwapCache(page_map))
                        delete_from_swap_cache(page_map);
                __free_page(page_map);
                /*
                 * Check for and clear any overflowed swap map counts.
                 */
                if (si->swap_map[i] != 0) {
                        if (si->swap_map[i] != SWAP_MAP_MAX)
                                printk(KERN_ERR
                                        "try_to_unuse: entry %08lx count=%d\n",
                                        entry, si->swap_map[i]);
                        si->swap_map[i] = 0;
                        nr_swap_pages++;
                }
        }
        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 (!capable(CAP_SYS_ADMIN))
                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 == dentry)
                                break;
                        if (S_ISBLK(dentry->d_inode->i_mode) &&
                            p->swap_device == dentry->d_inode->i_rdev)
                                break;
                }
                prev = type;
        }
        err = -EINVAL;
        if (type < 0)
                goto out_dput;

        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) {
                /* 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_dput;
        }
        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);

        dentry = p->swap_file;
        p->swap_file = NULL;
        nr_swap_pages -= p->pages;
        p->swap_device = 0;
        vfree(p->swap_map);
        p->swap_map = NULL;
        vfree(p->swap_lockmap);
        p->swap_lockmap = NULL;
        p->flags = 0;
        err = 0;

out_dput:
        dput(dentry);
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) && ptr->swap_map) {
                        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 SWAP_MAP_BAD:
                                        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;
        union swap_header *swap_header = 0;
        int swap_header_version;
        int lock_map_size = PAGE_SIZE;
        int nr_good_pages = 0;
        unsigned long tmp_lock_map = 0;
        int swapfilesize;
        
        lock_kernel();
        if (!capable(CAP_SYS_ADMIN))
                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)) {
                kdev_t dev = swap_dentry->d_inode->i_rdev;

                p->swap_device = dev;
                set_blocksize(dev, 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;
                set_blocksize(dev, PAGE_SIZE);
                error = -ENODEV;
                if (!dev || (blk_size[MAJOR(dev)] &&
                             !blk_size[MAJOR(dev)][MINOR(dev)]))
                        goto bad_swap;
                error = -EBUSY;
                for (i = 0 ; i < nr_swapfiles ; i++) {
                        if (i == type)
                                continue;
                        if (dev == swap_info[i].swap_device)
                                goto bad_swap;
                }
                swapfilesize = 0;
                if (blk_size[MAJOR(dev)])
                        swapfilesize = blk_size[MAJOR(dev)][MINOR(dev)]
                                >> (PAGE_SHIFT - 10);
        } else if (S_ISREG(swap_dentry->d_inode->i_mode)) {
                error = -EBUSY;
                for (i = 0 ; i < nr_swapfiles ; i++) {
                        if (i == type || !swap_info[i].swap_file)
                                continue;
                        if (swap_dentry->d_inode == swap_info[i].swap_file->d_inode)
                                goto bad_swap;
                }
                swapfilesize = swap_dentry->d_inode->i_size  >> PAGE_SHIFT;
        } else
                goto bad_swap;

        swap_header = (void *) __get_free_page(GFP_USER);
        if (!swap_header) {
                printk("Unable to start swapping: out of memory :-)\n");
                error = -ENOMEM;
                goto bad_swap;
        }

        p->swap_lockmap = (char *) &tmp_lock_map;
        rw_swap_page_nocache(READ, SWP_ENTRY(type,0), (char *) swap_header);
        p->swap_lockmap = NULL;

        if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
                swap_header_version = 1;
        else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
                swap_header_version = 2;
        else {
                printk("Unable to find swap-space signature\n");
                error = -EINVAL;
                goto bad_swap;
        }
        
        switch (swap_header_version) {
        case 1:
                memset(((char *) swap_header)+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,(char *) swap_header)) {
                                if (!p->lowest_bit)
                                        p->lowest_bit = i;
                                p->highest_bit = i;
                                p->max = i+1;
                                j++;
                        }
                }
                nr_good_pages = j;
                p->swap_map = vmalloc(p->max * sizeof(short));
                if (!p->swap_map) {
                        error = -ENOMEM;                
                        goto bad_swap;
                }
                for (i = 1 ; i < p->max ; i++) {
                        if (test_bit(i,(char *) swap_header))
                                p->swap_map[i] = 0;
                        else
                                p->swap_map[i] = SWAP_MAP_BAD;
                }
                break;

        case 2:
                /* Check the swap header's sub-version and the size of
                   the swap file and bad block lists */
                if (swap_header->info.version != 1) {
                        printk(KERN_WARNING
                               "Unable to handle swap header version %d\n",
                               swap_header->info.version);
                        error = -EINVAL;
                        goto bad_swap;
                }

                p->lowest_bit  = 1;
                p->highest_bit = swap_header->info.last_page - 1;
                p->max         = swap_header->info.last_page;

                error = -EINVAL;
                if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
                        goto bad_swap;
                if (p->max >= SWP_OFFSET(SWP_ENTRY(0,~0UL)))
                        goto bad_swap;
                
                /* OK, set up the swap map and apply the bad block list */
                if (!(p->swap_map = vmalloc (p->max * sizeof(short)))) {
                        error = -ENOMEM;
                        goto bad_swap;
                }

                error = 0;
                memset(p->swap_map, 0, p->max * sizeof(short));
                for (i=0; i<swap_header->info.nr_badpages; i++) {
                        int page = swap_header->info.badpages[i];
                        if (page <= 0 || page >= swap_header->info.last_page)
                                error = -EINVAL;
                        else
                                p->swap_map[page] = SWAP_MAP_BAD;
                }
                nr_good_pages = swap_header->info.last_page -
                                swap_header->info.nr_badpages - 1;
                lock_map_size = (p->max + 7) / 8;
                if (error) 
                        goto bad_swap;
        }

        if (swapfilesize && p->max > swapfilesize) {
                printk(KERN_WARNING
                       "Swap area shorter than signature indicates\n");
                error = -EINVAL;
                goto bad_swap;
        }
        if (!nr_good_pages) {
                printk(KERN_WARNING "Empty swap-file\n");
                error = -EINVAL;
                goto bad_swap;
        }
        p->swap_map[0] = SWAP_MAP_BAD;
        if (!(p->swap_lockmap = vmalloc (lock_map_size))) {
                error = -ENOMEM;
                goto bad_swap;
        }
        memset(p->swap_lockmap,0,lock_map_size);
        p->flags = SWP_WRITEOK;
        p->pages = nr_good_pages;
        nr_swap_pages += nr_good_pages;
        printk(KERN_INFO "Adding Swap: %dk swap-space (priority %d)\n",
               nr_good_pages<<(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:
        if (p->swap_lockmap)
                vfree(p->swap_lockmap);
        if (p->swap_map)
                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;
        if (!(swap_flags & SWAP_FLAG_PREFER))
                ++least_priority;
out:
        if (swap_header)
                free_page((long) swap_header);
        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 SWAP_MAP_BAD:
                                        continue;
                                case 0:
                                        ++val->freeswap;
                                default:
                                        ++val->totalswap;
                        }
        }
        val->freeswap <<= PAGE_SHIFT;
        val->totalswap <<= PAGE_SHIFT;
        return;
}