/*
 *  linux/fs/file_table.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
 */

#include <linux/string.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/iobuf.h>
#include <linux/fs.h>
#include <linux/security.h>

/* sysctl tunables... */
struct files_stat_struct files_stat = {0, 0, NR_FILE};

/* Here the new files go */
static LIST_HEAD(anon_list);
/* And here the free ones sit */
static LIST_HEAD(free_list);
/* public *and* exported. Not pretty! */
spinlock_t files_lock = SPIN_LOCK_UNLOCKED;

/* 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.
 *
 * SMP-safe.
 */
struct file * get_empty_filp(void)
{
        static int old_max = 0;
        struct file * f;

        file_list_lock();
        if (files_stat.nr_free_files > NR_RESERVED_FILES) {
        used_one:
                f = list_entry(free_list.next, struct file, f_list);
                list_del(&f->f_list);
                files_stat.nr_free_files--;
        new_one:
                memset(f, 0, sizeof(*f));
                if (security_ops->file_alloc_security(f)) {
                        list_add(&f->f_list, &free_list);
                        files_stat.nr_free_files++;
                        file_list_unlock();
                        return NULL;
                }
                atomic_set(&f->f_count,1);
                f->f_version = ++event;
                f->f_uid = current->fsuid;
                f->f_gid = current->fsgid;
                f->f_owner.lock = RW_LOCK_UNLOCKED;
                list_add(&f->f_list, &anon_list);
                file_list_unlock();
                return f;
        }
        /*
         * Use a reserved one if we're the superuser
         */
        if (files_stat.nr_free_files && !current->euid)
                goto used_one;
        /*
         * Allocate a new one if we're below the limit.
         */
        if (files_stat.nr_files < files_stat.max_files) {
                file_list_unlock();
                f = kmem_cache_alloc(filp_cachep, SLAB_KERNEL);
                file_list_lock();
                if (f) {
                        files_stat.nr_files++;
                        goto new_one;
                }
                /* Big problems... */
                printk(KERN_WARNING "VFS: filp allocation failed\n");

        } else if (files_stat.max_files > old_max) {
                printk(KERN_INFO "VFS: file-max limit %d reached\n", files_stat.max_files);
                old_max = files_stat.max_files;
        }
        file_list_unlock();
        return NULL;
}

/*
 * Clear and initialize a (private) struct file for the given dentry,
 * and call the open function (if any).  The caller must verify that
 * inode->i_fop is not NULL.
 */
int init_private_file(struct file *filp, struct dentry *dentry, int mode)
{
        memset(filp, 0, sizeof(*filp));
        filp->f_mode   = mode;
        atomic_set(&filp->f_count, 1);
        filp->f_dentry = dentry;
        filp->f_uid    = current->fsuid;
        filp->f_gid    = current->fsgid;
        filp->f_op     = dentry->d_inode->i_fop;
        if (filp->f_op->open)
                return filp->f_op->open(dentry->d_inode, filp);
        else
                return 0;
}

void fput(struct file * file)
{
        if (atomic_dec_and_test(&file->f_count))
                __fput(file);
}

/* __fput is called from task context when aio completion releases the last
 * last use of a struct file *.  Do not use otherwise.
 */
void __fput(struct file * file)
{
        struct dentry * dentry = file->f_dentry;
        struct vfsmount * mnt = file->f_vfsmnt;
        struct inode * inode = dentry->d_inode;

        locks_remove_flock(file);

        if (file->f_op && file->f_op->release)
                file->f_op->release(inode, file);
        security_ops->file_free_security(file);
        fops_put(file->f_op);
        if (file->f_mode & FMODE_WRITE)
                put_write_access(inode);
        file_list_lock();
        file->f_dentry = NULL;
        file->f_vfsmnt = NULL;
        list_del(&file->f_list);
        list_add(&file->f_list, &free_list);
        files_stat.nr_free_files++;
        file_list_unlock();
        dput(dentry);
        mntput(mnt);
}

struct file * fget(unsigned int fd)
{
        struct file * file;
        struct files_struct *files = current->files;

        read_lock(&files->file_lock);
        file = fcheck(fd);
        if (file)
                get_file(file);
        read_unlock(&files->file_lock);
        return file;
}

/* Here. put_filp() is SMP-safe now. */

void put_filp(struct file *file)
{
        if(atomic_dec_and_test(&file->f_count)) {
                security_ops->file_free_security(file);
                file_list_lock();
                list_del(&file->f_list);
                list_add(&file->f_list, &free_list);
                files_stat.nr_free_files++;
                file_list_unlock();
        }
}

void file_move(struct file *file, struct list_head *list)
{
        if (!list)
                return;
        file_list_lock();
        list_del(&file->f_list);
        list_add(&file->f_list, list);
        file_list_unlock();
}

int fs_may_remount_ro(struct super_block *sb)
{
        struct list_head *p;

        /* Check that no files are currently opened for writing. */
        file_list_lock();
        list_for_each(p, &sb->s_files) {
                struct file *file = list_entry(p, struct file, f_list);
                struct inode *inode = file->f_dentry->d_inode;

                /* File with pending delete? */
                if (inode->i_nlink == 0)
                        goto too_bad;

                /* Writable file? */
                if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
                        goto too_bad;
        }
        file_list_unlock();
        return 1; /* Tis' cool bro. */
too_bad:
        file_list_unlock();
        return 0;
}

void __init files_init(unsigned long mempages)
{ 
        int n; 
        /* One file with associated inode and dcache is very roughly 1K. 
         * Per default don't use more than 10% of our memory for files. 
         */ 

        n = (mempages * (PAGE_SIZE / 1024)) / 10;
        files_stat.max_files = n; 
        if (files_stat.max_files < NR_FILE)
                files_stat.max_files = NR_FILE;
}