/* *  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/lglock.h>#include <linux/percpu_counter.h>#include <linux/percpu.h>#include <linux/hardirq.h>#include <linux/task_work.h>#include <linux/ima.h> #include <linux/atomic.h> #include "internal.h" /* sysctl tunables... */struct files_stat_struct files_stat = {	.max_files = NR_FILE}; /* SLAB cache for file structures */static struct kmem_cache *filp_cachep __read_mostly; static struct percpu_counter nr_files __cacheline_aligned_in_smp; static 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 long get_nr_files(void){	return percpu_counter_read_positive(&nr_files);} /* * Return the maximum number of open files in the system */unsigned long 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_doulongvec_minmax(table, write, buffer, lenp, ppos);}#elseint 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 an error pointer if some error happend e.g. we over file * structures limit, run out of memory or operation is not permitted. * * 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 long old_max;	struct file *f;	int error; 	/*	 * 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 (unlikely(!f))		return ERR_PTR(-ENOMEM); 	percpu_counter_inc(&nr_files);	f->f_cred = get_cred(cred);	error = security_file_alloc(f);	if (unlikely(error)) {		file_free(f);		return ERR_PTR(error);	} 	atomic_long_set(&f->f_count, 1);	rwlock_init(&f->f_owner.lock);	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) {		pr_info("VFS: file-max limit %lu reached\n", get_max_files());		old_max = get_nr_files();	}	return ERR_PTR(-ENFILE);} /** * 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 (IS_ERR(file))		return file; 	file->f_path = *path;	file->f_inode = path->dentry->d_inode;	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));	}	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)		i_readcount_inc(path->dentry->d_inode);	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. */static 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);} /* 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 = file->f_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 (unlikely(file->f_flags & FASYNC)) {		if (file->f_op->fasync)			file->f_op->fasync(-1, file, 0);	}	ima_file_free(file);	if (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 &&		     !(file->f_mode & FMODE_PATH))) {		cdev_put(inode->i_cdev);	}	fops_put(file->f_op);	put_pid(file->f_owner.pid);	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)		i_readcount_dec(inode);	if (file->f_mode & FMODE_WRITE)		drop_file_write_access(file);	file->f_path.dentry = NULL;	file->f_path.mnt = NULL;	file->f_inode = NULL;	file_free(file);	dput(dentry);	mntput(mnt);} static LLIST_HEAD(delayed_fput_list);static void delayed_fput(struct work_struct *unused){	struct llist_node *node = llist_del_all(&delayed_fput_list);	struct llist_node *next; 	for (; node; node = next) {		next = llist_next(node);		__fput(llist_entry(node, struct file, f_u.fu_llist));	}} static void ____fput(struct callback_head *work){	__fput(container_of(work, struct file, f_u.fu_rcuhead));} /* * If kernel thread really needs to have the final fput() it has done * to complete, call this.  The only user right now is the boot - we * *do* need to make sure our writes to binaries on initramfs has * not left us with opened struct file waiting for __fput() - execve() * won't work without that.  Please, don't add more callers without * very good reasons; in particular, never call that with locks * held and never call that from a thread that might need to do * some work on any kind of umount. */void flush_delayed_fput(void){	delayed_fput(NULL);} static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput); void fput(struct file *file){	if (atomic_long_dec_and_test(&file->f_count)) {		struct task_struct *task = current; 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {			init_task_work(&file->f_u.fu_rcuhead, ____fput);			if (!task_work_add(task, &file->f_u.fu_rcuhead, true))				return;			/*			 * After this task has run exit_task_work(),			 * task_work_add() will fail.  Fall through to delayed			 * fput to avoid leaking *file.			 */		} 		if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))			schedule_delayed_work(&delayed_fput_work, 1);	}} /* * synchronous analog of fput(); for kernel threads that might be needed * in some umount() (and thus can't use flush_delayed_fput() without * risking deadlocks), need to wait for completion of __fput() and know * for this specific struct file it won't involve anything that would * need them.  Use only if you really need it - at the very least, * don't blindly convert fput() by kernel thread to that. */void __fput_sync(struct file *file){	if (atomic_long_dec_and_test(&file->f_count)) {		struct task_struct *task = current;		BUG_ON(!(task->flags & PF_KTHREAD));		__fput(file);	}} EXPORT_SYMBOL(fput); void put_filp(struct file *file){	if (atomic_long_dec_and_test(&file->f_count)) {		security_file_free(file);		file_free(file);	}} void __init files_init(unsigned long mempages){ 	unsigned long 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 = max_t(unsigned long, n, NR_FILE);	files_defer_init();	percpu_counter_init(&nr_files, 0);}