/*
* 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/fdtable.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 <linux/ima.h>
#include <asm/atomic.h>
#include "internal.h"
/* sysctl tunables... */
struct files_stat_struct files_stat = {
.max_files = NR_FILE
};
/* public. Not pretty! */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
/* SLAB cache for file structures */
static struct kmem_cache *filp_cachep __read_mostly;
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);
put_cred(f->f_cred);
kmem_cache_free(filp_cachep, f);
}
static inline void file_free(struct file *f)
{
percpu_counter_dec(&nr_files);
file_check_state(f);
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,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
files_stat.nr_files = get_nr_files();
return proc_dointvec(table, write, buffer, lenp, ppos);
}
#else
int proc_nr_files(ctl_table *table, int write,
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.
*
* Be very careful using this. You are responsible for
* getting write access to any mount that you might assign
* to this filp, if it is opened for write. If this is not
* done, you will imbalance int the mount's writer count
* and a warning at __fput() time.
*/
struct file *get_empty_filp(void)
{
const struct cred *cred = current_cred();
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;
INIT_LIST_HEAD(&f->f_u.fu_list);
atomic_long_set(&f->f_count, 1);
rwlock_init(&f->f_owner.lock);
f->f_cred = get_cred(cred);
spin_lock_init(&f->f_lock);
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;
}
/**
* 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 path *path, fmode_t mode,
const struct file_operations *fop)
{
struct file *file;
file = get_empty_filp();
if (!file)
return NULL;
file->f_path = *path;
file->f_mapping = path->dentry->d_inode->i_mapping;
file->f_mode = mode;
file->f_op = fop;
/*
* These mounts don't really matter in practice
* for r/o bind mounts. They aren't userspace-
* visible. We do this for consistency, and so
* that we can do debugging checks at __fput()
*/
if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
file_take_write(file);
WARN_ON(mnt_clone_write(path->mnt));
}
ima_counts_get(file);
return file;
}
EXPORT_SYMBOL(alloc_file);
/**
* drop_file_write_access - give up ability to write to a file
* @file: the file to which we will stop writing
*
* This is a central place which will give up the ability
* to write to @file, along with access to write through
* its vfsmount.
*/
void drop_file_write_access(struct file *file)
{
struct vfsmount *mnt = file->f_path.mnt;
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
put_write_access(inode);
if (special_file(inode->i_mode))
return;
if (file_check_writeable(file) != 0)
return;
mnt_drop_write(mnt);
file_release_write(file);
}
EXPORT_SYMBOL_GPL(drop_file_write_access);
/* the real guts of fput() - releasing the last reference to file
*/
static void __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);
/*
* fsnotify_create_event may have taken one or more references on this
* file. If it did so it left one reference for us to drop to make sure
* its calls to fput could not prematurely destroy the file.
*/
if (atomic_long_read(&file->f_count))
return fput(file);
/*
* The function eventpoll_release() should be the first called
* in the file cleanup chain.
*/
eventpoll_release(file);
locks_remove_flock(file);
if (unlikely(file->f_flags & FASYNC)) {
if (file->f_op && file->f_op->fasync)
file->f_op->fasync(-1, file, 0);
}
if (file->f_op && file->f_op->release)
file->f_op->release(inode, file);
security_file_free(file);
ima_file_free(file);
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
cdev_put(inode->i_cdev);
fops_put(file->f_op);
put_pid(file->f_owner.pid);
file_kill(file);
if (file->f_mode & FMODE_WRITE)
drop_file_write_access(file);
file->f_path.dentry = NULL;
file->f_path.mnt = NULL;
file_free(file);
dput(dentry);
mntput(mnt);
}
void fput(struct file *file)
{
if (atomic_long_dec_and_test(&file->f_count))
__fput(file);
}
EXPORT_SYMBOL(fput);
struct file *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_long_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 *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_long_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_long_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;
}
/**
* mark_files_ro - mark all files read-only
* @sb: superblock in question
*
* All files are marked read-only. We don't care about pending
* delete files so this should be used in 'force' mode only.
*/
void mark_files_ro(struct super_block *sb)
{
struct file *f;
retry:
file_list_lock();
list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
struct vfsmount *mnt;
if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
continue;
if (!file_count(f))
continue;
if (!(f->f_mode & FMODE_WRITE))
continue;
spin_lock(&f->f_lock);
f->f_mode &= ~FMODE_WRITE;
spin_unlock(&f->f_lock);
if (file_check_writeable(f) != 0)
continue;
file_release_write(f);
mnt = mntget(f->f_path.mnt);
file_list_unlock();
/*
* This can sleep, so we can't hold
* the file_list_lock() spinlock.
*/
mnt_drop_write(mnt);
mntput(mnt);
goto retry;
}
file_list_unlock();
}
void __init files_init(unsigned long mempages)
{
int n;
filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
/*
* 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);
}
