| /* |
| * 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 |
| }; |
| |
| DEFINE_STATIC_LGLOCK(files_lglock); |
| |
| /* 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); |
| } |
| #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 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); |
| } |
| |
| INIT_LIST_HEAD(&f->f_u.fu_list); |
| 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 && file->f_op->fasync) |
| file->f_op->fasync(-1, file, 0); |
| } |
| ima_file_free(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 && |
| !(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 DEFINE_SPINLOCK(delayed_fput_lock); |
| static LIST_HEAD(delayed_fput_list); |
| static void delayed_fput(struct work_struct *unused) |
| { |
| LIST_HEAD(head); |
| spin_lock_irq(&delayed_fput_lock); |
| list_splice_init(&delayed_fput_list, &head); |
| spin_unlock_irq(&delayed_fput_lock); |
| while (!list_empty(&head)) { |
| struct file *f = list_first_entry(&head, struct file, f_u.fu_list); |
| list_del_init(&f->f_u.fu_list); |
| __fput(f); |
| } |
| } |
| |
| 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_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; |
| unsigned long flags; |
| |
| file_sb_list_del(file); |
| 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. free_ipc_ns()-> |
| * shm_destroy() can do this. Fall through to delayed |
| * fput to avoid leaking *file. |
| */ |
| } |
| spin_lock_irqsave(&delayed_fput_lock, flags); |
| list_add(&file->f_u.fu_list, &delayed_fput_list); |
| schedule_work(&delayed_fput_work); |
| spin_unlock_irqrestore(&delayed_fput_lock, flags); |
| } |
| } |
| |
| /* |
| * 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; |
| file_sb_list_del(file); |
| 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_sb_list_del(file); |
| file_free(file); |
| } |
| } |
| |
| static inline int file_list_cpu(struct file *file) |
| { |
| #ifdef CONFIG_SMP |
| return file->f_sb_list_cpu; |
| #else |
| return smp_processor_id(); |
| #endif |
| } |
| |
| /* helper for file_sb_list_add to reduce ifdefs */ |
| static inline void __file_sb_list_add(struct file *file, struct super_block *sb) |
| { |
| struct list_head *list; |
| #ifdef CONFIG_SMP |
| int cpu; |
| cpu = smp_processor_id(); |
| file->f_sb_list_cpu = cpu; |
| list = per_cpu_ptr(sb->s_files, cpu); |
| #else |
| list = &sb->s_files; |
| #endif |
| list_add(&file->f_u.fu_list, list); |
| } |
| |
| /** |
| * file_sb_list_add - add a file to the sb's file list |
| * @file: file to add |
| * @sb: sb to add it to |
| * |
| * Use this function to associate a file with the superblock of the inode it |
| * refers to. |
| */ |
| void file_sb_list_add(struct file *file, struct super_block *sb) |
| { |
| lg_local_lock(&files_lglock); |
| __file_sb_list_add(file, sb); |
| lg_local_unlock(&files_lglock); |
| } |
| |
| /** |
| * file_sb_list_del - remove a file from the sb's file list |
| * @file: file to remove |
| * @sb: sb to remove it from |
| * |
| * Use this function to remove a file from its superblock. |
| */ |
| void file_sb_list_del(struct file *file) |
| { |
| if (!list_empty(&file->f_u.fu_list)) { |
| lg_local_lock_cpu(&files_lglock, file_list_cpu(file)); |
| list_del_init(&file->f_u.fu_list); |
| lg_local_unlock_cpu(&files_lglock, file_list_cpu(file)); |
| } |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * These macros iterate all files on all CPUs for a given superblock. |
| * files_lglock must be held globally. |
| */ |
| #define do_file_list_for_each_entry(__sb, __file) \ |
| { \ |
| int i; \ |
| for_each_possible_cpu(i) { \ |
| struct list_head *list; \ |
| list = per_cpu_ptr((__sb)->s_files, i); \ |
| list_for_each_entry((__file), list, f_u.fu_list) |
| |
| #define while_file_list_for_each_entry \ |
| } \ |
| } |
| |
| #else |
| |
| #define do_file_list_for_each_entry(__sb, __file) \ |
| { \ |
| struct list_head *list; \ |
| list = &(sb)->s_files; \ |
| list_for_each_entry((__file), list, f_u.fu_list) |
| |
| #define while_file_list_for_each_entry \ |
| } |
| |
| #endif |
| |
| /** |
| * 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; |
| |
| lg_global_lock(&files_lglock); |
| do_file_list_for_each_entry(sb, f) { |
| if (!S_ISREG(file_inode(f)->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; |
| __mnt_drop_write(f->f_path.mnt); |
| file_release_write(f); |
| } while_file_list_for_each_entry; |
| lg_global_unlock(&files_lglock); |
| } |
| |
| 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(); |
| lg_lock_init(&files_lglock, "files_lglock"); |
| percpu_counter_init(&nr_files, 0); |
| } |