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/*

 *  linux/fs/file_table.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 */

#include <linux/config.h>

#include <linux/stddef.h>

#include <linux/fs.h>

#include <linux/string.h>

#include <linux/mm.h>

/*

 * first_file points to a doubly linked list of all file structures in

 *            the system.

 * nr_files   holds the length of this list.

 */

struct file * first_file = NULL;

int nr_files = 0;

int max_files = NR_FILE;

/*

 * Insert a new file structure at the head of the list of available ones.

 */

static inline void insert_file_free(struct file *file)

{

        struct file *next, *prev;

        next = first_file;

        first_file = file;

        file->f_count = 0;

        prev = next->f_prev;

        file->f_next = next;

        next->f_prev = file;

        file->f_prev = prev;

        prev->f_next = file;

}

/*

 * Remove a file structure from the list of available ones.

 */

static inline void remove_file_free(struct file *file)

{

        struct file *next, *prev;

        next = file->f_next;

        prev = file->f_prev;

        file->f_next = file->f_prev = NULL;

        if (first_file == file)

                first_file = next;

        next->f_prev = prev;

        prev->f_next = next;

}

/*

 * Insert a file structure at the end of the list of available ones.

 */

static inline void put_last_free(struct file *file)

{

        struct file *next, *prev;

        next = first_file;

        file->f_next = next;

        prev = next->f_prev;

        next->f_prev = file;

        file->f_prev = prev;

        prev->f_next = file;

}

/*

 * Allocate a new memory page for file structures and

 * insert the new structures into the global list.

 * Returns 0, if there is no more memory, 1 otherwise.

 */

static int grow_files(void)

{

        struct file * file;

        int i;

        /*

         * We don't have to clear the page because we only look into

         * f_count, f_prev and f_next and they get initialized in

         * insert_file_free.  The rest of the file structure is cleared

         * by get_empty_filp before it is returned.

         */

        file = (struct file *) __get_free_page(GFP_KERNEL);

        if (!file)

                return 0;

        nr_files += i = PAGE_SIZE/sizeof(struct file);

        if (!first_file)

                file->f_count = 0,

                file->f_next = file->f_prev = first_file = file++,

                i--;

        for (; i ; i--)

                insert_file_free(file++);

        return 1;

}

unsigned long file_table_init(unsigned long start, unsigned long end)

{

        return start;

}

/*

 * Find an unused file structure and return a pointer to it.

 * Returns NULL, if there are no more free file structures or

 * we run out of memory.

 */

struct file * get_empty_filp(void)

{

        int i;

        int max = max_files;

        struct file * f;

        /*

         * Reserve a few files for the super-user..

         */

        if (current->euid)

                max -= 10;

        /* if the return is taken, we are in deep trouble */

        if (!first_file && !grow_files())

                return NULL;

        do {

                for (f = first_file, i=0; i < nr_files; i++, f = f->f_next)

                        if (!f->f_count) {

                                /* The f_next pointer is followed by the f_prev pointer */

                                memset(f, 0, offsetof(struct file, f_next));

                                memset(&f->f_prev + 1, 0, sizeof(*f) - sizeof(f->f_prev) - offsetof(struct file, f_prev));

                                f->f_count = 1;

                                f->f_version = ++event;

                                first_file = f->f_next;

                                return f;

                        }

        } while (nr_files < max && grow_files());

        return NULL;

}

#ifdef CONFIG_QUOTA

void add_dquot_ref(kdev_t dev, short type)

{

        struct file *filp;

        int cnt;

        for (filp = first_file, cnt = 0; cnt < nr_files; cnt++, filp = filp->f_next) {

                if (!filp->f_count || !filp->f_inode || filp->f_inode->i_dev != dev)

                        continue;

                if (filp->f_mode & FMODE_WRITE && filp->f_inode->i_sb->dq_op) {

                        filp->f_inode->i_sb->dq_op->initialize(filp->f_inode, type);

                        filp->f_inode->i_flags |= S_WRITE;

                }

        }

}

void reset_dquot_ptrs(kdev_t dev, short type)

{

        struct file *filp;

        int cnt;

        for (filp = first_file, cnt = 0; cnt < nr_files; cnt++, filp = filp->f_next) {

                if (!filp->f_count || !filp->f_inode || filp->f_inode->i_dev != dev)

                        continue;

                if (IS_WRITABLE(filp->f_inode)) {

                        filp->f_inode->i_dquot[type] = NODQUOT;

                        filp->f_inode->i_flags &= ~S_WRITE;

                }

        }

}

#endif