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/*

 *  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/fs.h>

#include <linux/security.h>

#include <linux/eventpoll.h>

#include <linux/rcupdate.h>

#include <linux/mount.h>

#include <linux/capability.h>

#include <linux/cdev.h>

#include <linux/fsnotify.h>

#include <linux/sysctl.h>

#include <linux/percpu_counter.h>

#include <asm/atomic.h>

/* sysctl tunables... */

struct files_stat_struct files_stat = {

        .max_files = NR_FILE

};

/* public. Not pretty! */

__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);

static struct percpu_counter nr_files __cacheline_aligned_in_smp;

static inline void file_free_rcu(struct rcu_head *head)

{

        struct file *f =  container_of(head, struct file, f_u.fu_rcuhead);

        kmem_cache_free(filp_cachep, f);

}

static inline void file_free(struct file *f)

{

        percpu_counter_dec(&nr_files);

        call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);

}

/*

 * Return the total number of open files in the system

 */

static int get_nr_files(void)

{

        return percpu_counter_read_positive(&nr_files);

}

/*

 * Return the maximum number of open files in the system

 */

int get_max_files(void)

{

        return files_stat.max_files;

}

EXPORT_SYMBOL_GPL(get_max_files);

/*

 * Handle nr_files sysctl

 */

#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)

int proc_nr_files(ctl_table *table, int write, struct file *filp,

                     void __user *buffer, size_t *lenp, loff_t *ppos)

{

        files_stat.nr_files = get_nr_files();

        return proc_dointvec(table, write, filp, buffer, lenp, ppos);

}

#else

int proc_nr_files(ctl_table *table, int write, struct file *filp,

                     void __user *buffer, size_t *lenp, loff_t *ppos)

{

        return -ENOSYS;

}

#endif

/* 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)

{

        struct task_struct *tsk;

        static int old_max;

        struct file * f;

        /*

         * Privileged users can go above max_files

         */

        if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {

                /*

                 * percpu_counters are inaccurate.  Do an expensive check before

                 * we go and fail.

                 */

                if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)

                        goto over;

        }

        f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);

        if (f == NULL)

                goto fail;

        percpu_counter_inc(&nr_files);

        if (security_file_alloc(f))

                goto fail_sec;

        tsk = current;

        INIT_LIST_HEAD(&f->f_u.fu_list);

        atomic_set(&f->f_count, 1);

        rwlock_init(&f->f_owner.lock);

        f->f_uid = tsk->fsuid;

        f->f_gid = tsk->fsgid;

        eventpoll_init_file(f);

        /* f->f_version: 0 */

        return f;

over:

        /* Ran out of filps - report that */

        if (get_nr_files() > old_max) {

                printk(KERN_INFO "VFS: file-max limit %d reached\n",

                                        get_max_files());

                old_max = get_nr_files();

        }

        goto fail;

fail_sec:

        file_free(f);

fail:

        return NULL;

}

EXPORT_SYMBOL(get_empty_filp);

/**

 * alloc_file - allocate and initialize a 'struct file'

 * @mnt: the vfsmount on which the file will reside

 * @dentry: the dentry representing the new file

 * @mode: the mode with which the new file will be opened

 * @fop: the 'struct file_operations' for the new file

 *

 * Use this instead of get_empty_filp() to get a new

 * 'struct file'.  Do so because of the same initialization

 * pitfalls reasons listed for init_file().  This is a

 * preferred interface to using init_file().

 *

 * If all the callers of init_file() are eliminated, its

 * code should be moved into this function.

 */

struct file *alloc_file(struct vfsmount *mnt, struct dentry *dentry,

                mode_t mode, const struct file_operations *fop)

{

        struct file *file;

        struct path;

        file = get_empty_filp();

        if (!file)

                return NULL;

        init_file(file, mnt, dentry, mode, fop);

        return file;

}

EXPORT_SYMBOL(alloc_file);

/**

 * init_file - initialize a 'struct file'

 * @file: the already allocated 'struct file' to initialized

 * @mnt: the vfsmount on which the file resides

 * @dentry: the dentry representing this file

 * @mode: the mode the file is opened with

 * @fop: the 'struct file_operations' for this file

 *

 * Use this instead of setting the members directly.  Doing so

 * avoids making mistakes like forgetting the mntget() or

 * forgetting to take a write on the mnt.

 *

 * Note: This is a crappy interface.  It is here to make

 * merging with the existing users of get_empty_filp()

 * who have complex failure logic easier.  All users

 * of this should be moving to alloc_file().

 */

int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry,

           mode_t mode, const struct file_operations *fop)

{

        int error = 0;

        file->f_path.dentry = dentry;

        file->f_path.mnt = mntget(mnt);

        file->f_mapping = dentry->d_inode->i_mapping;

        file->f_mode = mode;

        file->f_op = fop;

        return error;

}

EXPORT_SYMBOL(init_file);

void fastcall fput(struct file *file)

{

        if (atomic_dec_and_test(&file->f_count))

                __fput(file);

}

EXPORT_SYMBOL(fput);

/* __fput is called from task context when aio completion releases the last

 * last use of a struct file *.  Do not use otherwise.

 */

void fastcall __fput(struct file *file)

{

        struct dentry *dentry = file->f_path.dentry;

        struct vfsmount *mnt = file->f_path.mnt;

        struct inode *inode = dentry->d_inode;

        might_sleep();

        fsnotify_close(file);

        /*

         * The function eventpoll_release() should be the first called

         * in the file cleanup chain.

         */

        eventpoll_release(file);

        locks_remove_flock(file);

        if (file->f_op && file->f_op->release)

                file->f_op->release(inode, file);

        security_file_free(file);

        if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))

                cdev_put(inode->i_cdev);

        fops_put(file->f_op);

        if (file->f_mode & FMODE_WRITE)

                put_write_access(inode);

        put_pid(file->f_owner.pid);

        file_kill(file);

        file->f_path.dentry = NULL;

        file->f_path.mnt = NULL;

        file_free(file);

        dput(dentry);

        mntput(mnt);

}

struct file fastcall *fget(unsigned int fd)

{

        struct file *file;

        struct files_struct *files = current->files;

        rcu_read_lock();

        file = fcheck_files(files, fd);

        if (file) {

                if (!atomic_inc_not_zero(&file->f_count)) {

                        /* File object ref couldn't be taken */

                        rcu_read_unlock();

                        return NULL;

                }

        }

        rcu_read_unlock();

        return file;

}

EXPORT_SYMBOL(fget);

/*

 * Lightweight file lookup - no refcnt increment if fd table isn't shared.

 * You can use this only if it is guranteed that the current task already

 * holds a refcnt to that file. That check has to be done at fget() only

 * and a flag is returned to be passed to the corresponding fput_light().

 * There must not be a cloning between an fget_light/fput_light pair.

 */

struct file fastcall *fget_light(unsigned int fd, int *fput_needed)

{

        struct file *file;

        struct files_struct *files = current->files;

        *fput_needed = 0;

        if (likely((atomic_read(&files->count) == 1))) {

                file = fcheck_files(files, fd);

        } else {

                rcu_read_lock();

                file = fcheck_files(files, fd);

                if (file) {

                        if (atomic_inc_not_zero(&file->f_count))

                                *fput_needed = 1;

                        else

                                /* Didn't get the reference, someone's freed */

                                file = NULL;

                }

                rcu_read_unlock();

        }

        return file;

}

void put_filp(struct file *file)

{

        if (atomic_dec_and_test(&file->f_count)) {

                security_file_free(file);

                file_kill(file);

                file_free(file);

        }

}

void file_move(struct file *file, struct list_head *list)

{

        if (!list)

                return;

        file_list_lock();

        list_move(&file->f_u.fu_list, list);

        file_list_unlock();

}

void file_kill(struct file *file)

{

        if (!list_empty(&file->f_u.fu_list)) {

                file_list_lock();

                list_del_init(&file->f_u.fu_list);

                file_list_unlock();

        }

}

int fs_may_remount_ro(struct super_block *sb)

{

        struct file *file;

        /* Check that no files are currently opened for writing. */

        file_list_lock();

        list_for_each_entry(file, &sb->s_files, f_u.fu_list) {

                struct inode *inode = file->f_path.dentry->d_inode;

                /* File with pending delete? */

                if (inode->i_nlink == 0)

                        goto too_bad;

                /* Writeable 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;

        files_defer_init();

        percpu_counter_init(&nr_files, 0);

}