1 files changed, 329 insertions, 0 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
new file mode 100644
index 000000000..3cea02778
--- /dev/null
+++ b/fs/file_table.c
@@ -0,0 +1,329 @@
+/*
+ *  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);
+	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(struct 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);
+}
+#else
+int proc_nr_files(struct 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);
+	mutex_init(&f->f_pos_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);
+}
+EXPORT_SYMBOL(get_empty_filp);
+
+/**
+ * alloc_file - allocate and initialize a 'struct file'
+ *
+ * @path: the (dentry, vfsmount) pair for the new file
+ * @mode: the mode with which the new file will be opened
+ * @fop: the 'struct file_operations' for the new file
+ */
+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;
+	if ((mode & FMODE_READ) &&
+	     likely(fop->read || fop->read_iter))
+		mode |= FMODE_CAN_READ;
+	if ((mode & FMODE_WRITE) &&
+	     likely(fop->write || fop->write_iter))
+		mode |= FMODE_CAN_WRITE;
+	file->f_mode = mode;
+	file->f_op = fop;
+	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+		i_readcount_inc(path->dentry->d_inode);
+	return file;
+}
+EXPORT_SYMBOL(alloc_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_file(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_WRITER) {
+		put_write_access(inode);
+		__mnt_drop_write(mnt);
+	}
+	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);
+	}
+}
+EXPORT_SYMBOL(put_filp);
+
+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);
+	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
+}