linux/fs/notify/dnotify/dnotify.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Directory notifications for Linux.
 *
 * Copyright (C) 2000,2001,2002 Stephen Rothwell
 *
 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
 * dnotify was largly rewritten to use the new fsnotify infrastructure
 */
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/dnotify.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>

static int dir_notify_enable __read_mostly = …;
#ifdef CONFIG_SYSCTL
static struct ctl_table dnotify_sysctls[] = …;
static void __init dnotify_sysctl_init(void)
{ … }
#else
#define dnotify_sysctl_init …
#endif

static struct kmem_cache *dnotify_struct_cache __ro_after_init;
static struct kmem_cache *dnotify_mark_cache __ro_after_init;
static struct fsnotify_group *dnotify_group __ro_after_init;

/*
 * dnotify will attach one of these to each inode (i_fsnotify_marks) which
 * is being watched by dnotify.  If multiple userspace applications are watching
 * the same directory with dnotify their information is chained in dn
 */
struct dnotify_mark { … };

/*
 * When a process starts or stops watching an inode the set of events which
 * dnotify cares about for that inode may change.  This function runs the
 * list of everything receiving dnotify events about this directory and calculates
 * the set of all those events.  After it updates what dnotify is interested in
 * it calls the fsnotify function so it can update the set of all events relevant
 * to this inode.
 */
static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
{ … }

/*
 * Mains fsnotify call where events are delivered to dnotify.
 * Find the dnotify mark on the relevant inode, run the list of dnotify structs
 * on that mark and determine which of them has expressed interest in receiving
 * events of this type.  When found send the correct process and signal and
 * destroy the dnotify struct if it was not registered to receive multiple
 * events.
 */
static int dnotify_handle_event(struct fsnotify_mark *inode_mark, u32 mask,
				struct inode *inode, struct inode *dir,
				const struct qstr *name, u32 cookie)
{ … }

static void dnotify_free_mark(struct fsnotify_mark *fsn_mark)
{ … }

static const struct fsnotify_ops dnotify_fsnotify_ops = …;

/*
 * Called every time a file is closed.  Looks first for a dnotify mark on the
 * inode.  If one is found run all of the ->dn structures attached to that
 * mark for one relevant to this process closing the file and remove that
 * dnotify_struct.  If that was the last dnotify_struct also remove the
 * fsnotify_mark.
 */
void dnotify_flush(struct file *filp, fl_owner_t id)
{ … }

/* this conversion is done only at watch creation */
static __u32 convert_arg(unsigned int arg)
{ … }

/*
 * If multiple processes watch the same inode with dnotify there is only one
 * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct
 * onto that mark.  This function either attaches the new dnotify_struct onto
 * that list, or it |= the mask onto an existing dnofiy_struct.
 */
static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark,
		     fl_owner_t id, int fd, struct file *filp, __u32 mask)
{ … }

/*
 * When a process calls fcntl to attach a dnotify watch to a directory it ends
 * up here.  Allocate both a mark for fsnotify to add and a dnotify_struct to be
 * attached to the fsnotify_mark.
 */
int fcntl_dirnotify(int fd, struct file *filp, unsigned int arg)
{ … }

static int __init dnotify_init(void)
{ … }

module_init(…) …