| /* |
| * 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/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); |
| |
| /* SLAB cache for file structures */ |
| static struct kmem_cache *filp_cachep __read_mostly; |
| |
| 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); |
| |
| 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 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, |
| void __user *buffer, size_t *lenp, loff_t *ppos) |
| { |
| files_stat.nr_files = get_nr_files(); |
| return proc_dointvec(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 NULL, if there are no more free file structures or |
| * we run out of memory. |
| * |
| * 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 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_positive(&nr_files) >= files_stat.max_files) |
| goto over; |
| } |
| |
| f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL); |
| if (f == NULL) |
| goto fail; |
| |
| percpu_counter_inc(&nr_files); |
| if (security_file_alloc(f)) |
| goto fail_sec; |
| |
| INIT_LIST_HEAD(&f->f_u.fu_list); |
| atomic_long_set(&f->f_count, 1); |
| rwlock_init(&f->f_owner.lock); |
| f->f_cred = get_cred(cred); |
| 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) { |
| 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); |
| |
| /** |
| * 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 vfsmount *mnt, struct dentry *dentry, |
| fmode_t mode, const struct file_operations *fop) |
| { |
| struct file *file; |
| |
| file = get_empty_filp(); |
| if (!file) |
| return NULL; |
| |
| init_file(file, mnt, dentry, mode, fop); |
| return file; |
| } |
| EXPORT_SYMBOL(alloc_file); |
| |
| /** |
| * init_file - initialize a 'struct file' |
| * @file: the already allocated 'struct file' to initialized |
| * @mnt: the vfsmount on which the file resides |
| * @dentry: the dentry representing this file |
| * @mode: the mode the file is opened with |
| * @fop: the 'struct file_operations' for this file |
| * |
| * Use this instead of setting the members directly. Doing so |
| * avoids making mistakes like forgetting the mntget() or |
| * forgetting to take a write on the mnt. |
| * |
| * Note: This is a crappy interface. It is here to make |
| * merging with the existing users of get_empty_filp() |
| * who have complex failure logic easier. All users |
| * of this should be moving to alloc_file(). |
| */ |
| int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry, |
| fmode_t mode, const struct file_operations *fop) |
| { |
| int error = 0; |
| file->f_path.dentry = dentry; |
| file->f_path.mnt = mntget(mnt); |
| file->f_mapping = 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(dentry->d_inode->i_mode)) { |
| file_take_write(file); |
| error = mnt_clone_write(mnt); |
| WARN_ON(error); |
| } |
| return error; |
| } |
| EXPORT_SYMBOL(init_file); |
| |
| void fput(struct file *file) |
| { |
| if (atomic_long_dec_and_test(&file->f_count)) |
| __fput(file); |
| } |
| |
| EXPORT_SYMBOL(fput); |
| |
| /** |
| * 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. |
| */ |
| 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); |
| } |
| EXPORT_SYMBOL_GPL(drop_file_write_access); |
| |
| /* __fput is called from task context when aio completion releases the last |
| * last use of a struct file *. Do not use otherwise. |
| */ |
| void __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 (unlikely(file->f_flags & FASYNC)) { |
| if (file->f_op && file->f_op->fasync) |
| file->f_op->fasync(-1, file, 0); |
| } |
| 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); |
| put_pid(file->f_owner.pid); |
| file_kill(file); |
| if (file->f_mode & FMODE_WRITE) |
| drop_file_write_access(file); |
| file->f_path.dentry = NULL; |
| file->f_path.mnt = NULL; |
| file_free(file); |
| dput(dentry); |
| mntput(mnt); |
| } |
| |
| struct file *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_long_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 *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_long_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_long_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 file *file; |
| |
| /* Check that no files are currently opened for writing. */ |
| file_list_lock(); |
| list_for_each_entry(file, &sb->s_files, 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; |
| } |
| |
| /** |
| * 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; |
| |
| retry: |
| file_list_lock(); |
| list_for_each_entry(f, &sb->s_files, f_u.fu_list) { |
| struct vfsmount *mnt; |
| if (!S_ISREG(f->f_path.dentry->d_inode->i_mode)) |
| continue; |
| if (!file_count(f)) |
| continue; |
| if (!(f->f_mode & FMODE_WRITE)) |
| continue; |
| f->f_mode &= ~FMODE_WRITE; |
| if (file_check_writeable(f) != 0) |
| continue; |
| file_release_write(f); |
| mnt = mntget(f->f_path.mnt); |
| file_list_unlock(); |
| /* |
| * This can sleep, so we can't hold |
| * the file_list_lock() spinlock. |
| */ |
| mnt_drop_write(mnt); |
| mntput(mnt); |
| goto retry; |
| } |
| file_list_unlock(); |
| } |
| |
| void __init files_init(unsigned long mempages) |
| { |
| int 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 = n; |
| if (files_stat.max_files < NR_FILE) |
| files_stat.max_files = NR_FILE; |
| files_defer_init(); |
| percpu_counter_init(&nr_files, 0); |
| } |