/* *  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/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);}#elseint 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(&nr_files) >= files_stat.max_files)			goto over;	} 	f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);	if (f == NULL)		goto fail; 	percpu_counter_inc(&nr_files);	memset(f, 0, sizeof(*f));	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); 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 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_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);}