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0eeca28300
inotify is intended to correct the deficiencies of dnotify, particularly its inability to scale and its terrible user interface: * dnotify requires the opening of one fd per each directory that you intend to watch. This quickly results in too many open files and pins removable media, preventing unmount. * dnotify is directory-based. You only learn about changes to directories. Sure, a change to a file in a directory affects the directory, but you are then forced to keep a cache of stat structures. * dnotify's interface to user-space is awful. Signals? inotify provides a more usable, simple, powerful solution to file change notification: * inotify's interface is a system call that returns a fd, not SIGIO. You get a single fd, which is select()-able. * inotify has an event that says "the filesystem that the item you were watching is on was unmounted." * inotify can watch directories or files. Inotify is currently used by Beagle (a desktop search infrastructure), Gamin (a FAM replacement), and other projects. See Documentation/filesystems/inotify.txt. Signed-off-by: Robert Love <rml@novell.com> Cc: John McCutchan <ttb@tentacle.dhs.org> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
262 lines
5.9 KiB
C
262 lines
5.9 KiB
C
/*
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* linux/fs/file_table.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
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*/
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/smp_lock.h>
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#include <linux/fs.h>
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#include <linux/security.h>
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#include <linux/eventpoll.h>
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#include <linux/mount.h>
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#include <linux/cdev.h>
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#include <linux/fsnotify.h>
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/* sysctl tunables... */
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struct files_stat_struct files_stat = {
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.max_files = NR_FILE
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};
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EXPORT_SYMBOL(files_stat); /* Needed by unix.o */
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/* public. Not pretty! */
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__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
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static DEFINE_SPINLOCK(filp_count_lock);
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/* slab constructors and destructors are called from arbitrary
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* context and must be fully threaded - use a local spinlock
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* to protect files_stat.nr_files
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*/
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void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags)
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{
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if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
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SLAB_CTOR_CONSTRUCTOR) {
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unsigned long flags;
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spin_lock_irqsave(&filp_count_lock, flags);
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files_stat.nr_files++;
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spin_unlock_irqrestore(&filp_count_lock, flags);
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}
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}
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void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
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{
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unsigned long flags;
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spin_lock_irqsave(&filp_count_lock, flags);
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files_stat.nr_files--;
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spin_unlock_irqrestore(&filp_count_lock, flags);
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}
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static inline void file_free(struct file *f)
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{
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kmem_cache_free(filp_cachep, f);
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}
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/* Find an unused file structure and return a pointer to it.
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* Returns NULL, if there are no more free file structures or
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* we run out of memory.
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*/
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struct file *get_empty_filp(void)
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{
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static int old_max;
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struct file * f;
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/*
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* Privileged users can go above max_files
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*/
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if (files_stat.nr_files >= files_stat.max_files &&
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!capable(CAP_SYS_ADMIN))
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goto over;
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f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
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if (f == NULL)
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goto fail;
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memset(f, 0, sizeof(*f));
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if (security_file_alloc(f))
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goto fail_sec;
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eventpoll_init_file(f);
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atomic_set(&f->f_count, 1);
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f->f_uid = current->fsuid;
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f->f_gid = current->fsgid;
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rwlock_init(&f->f_owner.lock);
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/* f->f_version: 0 */
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INIT_LIST_HEAD(&f->f_list);
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f->f_maxcount = INT_MAX;
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return f;
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over:
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/* Ran out of filps - report that */
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if (files_stat.nr_files > old_max) {
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printk(KERN_INFO "VFS: file-max limit %d reached\n",
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files_stat.max_files);
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old_max = files_stat.nr_files;
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}
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goto fail;
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fail_sec:
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file_free(f);
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fail:
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return NULL;
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}
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EXPORT_SYMBOL(get_empty_filp);
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void fastcall fput(struct file *file)
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{
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if (atomic_dec_and_test(&file->f_count))
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__fput(file);
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}
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EXPORT_SYMBOL(fput);
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/* __fput is called from task context when aio completion releases the last
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* last use of a struct file *. Do not use otherwise.
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*/
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void fastcall __fput(struct file *file)
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{
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struct dentry *dentry = file->f_dentry;
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struct vfsmount *mnt = file->f_vfsmnt;
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struct inode *inode = dentry->d_inode;
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might_sleep();
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fsnotify_close(file);
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/*
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* The function eventpoll_release() should be the first called
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* in the file cleanup chain.
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*/
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eventpoll_release(file);
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locks_remove_flock(file);
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if (file->f_op && file->f_op->release)
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file->f_op->release(inode, file);
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security_file_free(file);
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if (unlikely(inode->i_cdev != NULL))
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cdev_put(inode->i_cdev);
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fops_put(file->f_op);
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if (file->f_mode & FMODE_WRITE)
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put_write_access(inode);
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file_kill(file);
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file->f_dentry = NULL;
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file->f_vfsmnt = NULL;
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file_free(file);
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dput(dentry);
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mntput(mnt);
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}
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struct file fastcall *fget(unsigned int fd)
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{
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struct file *file;
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struct files_struct *files = current->files;
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spin_lock(&files->file_lock);
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file = fcheck_files(files, fd);
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if (file)
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get_file(file);
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spin_unlock(&files->file_lock);
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return file;
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}
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EXPORT_SYMBOL(fget);
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/*
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* Lightweight file lookup - no refcnt increment if fd table isn't shared.
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* You can use this only if it is guranteed that the current task already
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* holds a refcnt to that file. That check has to be done at fget() only
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* and a flag is returned to be passed to the corresponding fput_light().
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* There must not be a cloning between an fget_light/fput_light pair.
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*/
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struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
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{
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struct file *file;
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struct files_struct *files = current->files;
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*fput_needed = 0;
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if (likely((atomic_read(&files->count) == 1))) {
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file = fcheck_files(files, fd);
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} else {
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spin_lock(&files->file_lock);
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file = fcheck_files(files, fd);
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if (file) {
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get_file(file);
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*fput_needed = 1;
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}
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spin_unlock(&files->file_lock);
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}
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return file;
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}
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void put_filp(struct file *file)
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{
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if (atomic_dec_and_test(&file->f_count)) {
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security_file_free(file);
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file_kill(file);
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file_free(file);
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}
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}
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void file_move(struct file *file, struct list_head *list)
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{
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if (!list)
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return;
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file_list_lock();
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list_move(&file->f_list, list);
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file_list_unlock();
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}
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void file_kill(struct file *file)
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{
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if (!list_empty(&file->f_list)) {
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file_list_lock();
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list_del_init(&file->f_list);
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file_list_unlock();
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}
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}
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int fs_may_remount_ro(struct super_block *sb)
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{
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struct list_head *p;
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/* Check that no files are currently opened for writing. */
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file_list_lock();
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list_for_each(p, &sb->s_files) {
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struct file *file = list_entry(p, struct file, f_list);
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struct inode *inode = file->f_dentry->d_inode;
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/* File with pending delete? */
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if (inode->i_nlink == 0)
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goto too_bad;
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/* Writeable file? */
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if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
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goto too_bad;
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}
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file_list_unlock();
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return 1; /* Tis' cool bro. */
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too_bad:
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file_list_unlock();
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return 0;
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}
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void __init files_init(unsigned long mempages)
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{
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int n;
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/* One file with associated inode and dcache is very roughly 1K.
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* Per default don't use more than 10% of our memory for files.
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*/
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n = (mempages * (PAGE_SIZE / 1024)) / 10;
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files_stat.max_files = n;
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if (files_stat.max_files < NR_FILE)
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files_stat.max_files = NR_FILE;
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}
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