--- /dev/null
+/*
+ * 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);
+}
+
+/**
+ * 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);
+ }
+}
+
+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);
+}
Code Review / kvmfornfv.git / blobdiff