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![Amir Goldstein](/assets/img/avatar_default.png)
Dirent events are going to be supported in two flavors: 1. Directory fid info + mask that includes the specific event types (e.g. FAN_CREATE) and an optional FAN_ONDIR flag. 2. Directory fid info + name + mask that includes only FAN_DIR_MODIFY. To request the second event flavor, user needs to set the event type FAN_DIR_MODIFY in the mark mask. The first flavor is supported since kernel v5.1 for groups initialized with flag FAN_REPORT_FID. It is intended to be used for watching directories in "batch mode" - the watcher is notified when directory is changed and re-scans the directory content in response. This event flavor is stored more compactly in the event queue, so it is optimal for workloads with frequent directory changes. The second event flavor is intended to be used for watching large directories, where the cost of re-scan of the directory on every change is considered too high. The watcher getting the event with the directory fid and entry name is expected to call fstatat(2) to query the content of the entry after the change. Legacy inotify events are reported with name and event mask (e.g. "foo", FAN_CREATE | FAN_ONDIR). That can lead users to the conclusion that there is *currently* an entry "foo" that is a sub-directory, when in fact "foo" may be negative or non-dir by the time user gets the event. To make it clear that the current state of the named entry is unknown, when reporting an event with name info, fanotify obfuscates the specific event types (e.g. create,delete,rename) and uses a common event type - FAN_DIR_MODIFY to describe the change. This should make it harder for users to make wrong assumptions and write buggy filesystem monitors. At this point, name info reporting is not yet implemented, so trying to set FAN_DIR_MODIFY in mark mask will return -EINVAL. Link: https://lore.kernel.org/r/20200319151022.31456-12-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
397 lines
11 KiB
C
397 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*/
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#include <linux/dcache.h>
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/srcu.h>
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#include <linux/fsnotify_backend.h>
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#include "fsnotify.h"
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/*
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* Clear all of the marks on an inode when it is being evicted from core
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*/
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void __fsnotify_inode_delete(struct inode *inode)
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{
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fsnotify_clear_marks_by_inode(inode);
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}
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EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
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void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
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{
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fsnotify_clear_marks_by_mount(mnt);
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}
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/**
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* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
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* @sb: superblock being unmounted.
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*
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* Called during unmount with no locks held, so needs to be safe against
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* concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
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*/
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static void fsnotify_unmount_inodes(struct super_block *sb)
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{
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struct inode *inode, *iput_inode = NULL;
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spin_lock(&sb->s_inode_list_lock);
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list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
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/*
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* We cannot __iget() an inode in state I_FREEING,
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* I_WILL_FREE, or I_NEW which is fine because by that point
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* the inode cannot have any associated watches.
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*/
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spin_lock(&inode->i_lock);
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if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
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spin_unlock(&inode->i_lock);
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continue;
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}
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/*
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* If i_count is zero, the inode cannot have any watches and
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* doing an __iget/iput with SB_ACTIVE clear would actually
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* evict all inodes with zero i_count from icache which is
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* unnecessarily violent and may in fact be illegal to do.
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* However, we should have been called /after/ evict_inodes
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* removed all zero refcount inodes, in any case. Test to
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* be sure.
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*/
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if (!atomic_read(&inode->i_count)) {
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spin_unlock(&inode->i_lock);
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continue;
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}
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__iget(inode);
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spin_unlock(&inode->i_lock);
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spin_unlock(&sb->s_inode_list_lock);
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if (iput_inode)
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iput(iput_inode);
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/* for each watch, send FS_UNMOUNT and then remove it */
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fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
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fsnotify_inode_delete(inode);
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iput_inode = inode;
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cond_resched();
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spin_lock(&sb->s_inode_list_lock);
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}
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spin_unlock(&sb->s_inode_list_lock);
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if (iput_inode)
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iput(iput_inode);
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/* Wait for outstanding inode references from connectors */
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wait_var_event(&sb->s_fsnotify_inode_refs,
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!atomic_long_read(&sb->s_fsnotify_inode_refs));
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}
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void fsnotify_sb_delete(struct super_block *sb)
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{
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fsnotify_unmount_inodes(sb);
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fsnotify_clear_marks_by_sb(sb);
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}
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/*
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* Given an inode, first check if we care what happens to our children. Inotify
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* and dnotify both tell their parents about events. If we care about any event
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* on a child we run all of our children and set a dentry flag saying that the
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* parent cares. Thus when an event happens on a child it can quickly tell if
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* if there is a need to find a parent and send the event to the parent.
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*/
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void __fsnotify_update_child_dentry_flags(struct inode *inode)
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{
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struct dentry *alias;
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int watched;
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if (!S_ISDIR(inode->i_mode))
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return;
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/* determine if the children should tell inode about their events */
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watched = fsnotify_inode_watches_children(inode);
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spin_lock(&inode->i_lock);
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/* run all of the dentries associated with this inode. Since this is a
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* directory, there damn well better only be one item on this list */
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hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
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struct dentry *child;
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/* run all of the children of the original inode and fix their
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* d_flags to indicate parental interest (their parent is the
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* original inode) */
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spin_lock(&alias->d_lock);
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list_for_each_entry(child, &alias->d_subdirs, d_child) {
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if (!child->d_inode)
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continue;
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spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
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if (watched)
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child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
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else
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child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
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spin_unlock(&child->d_lock);
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}
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spin_unlock(&alias->d_lock);
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}
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spin_unlock(&inode->i_lock);
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}
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/* Notify this dentry's parent about a child's events. */
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int fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
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int data_type)
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{
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struct dentry *parent;
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struct inode *p_inode;
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int ret = 0;
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if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
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return 0;
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parent = dget_parent(dentry);
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p_inode = parent->d_inode;
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if (unlikely(!fsnotify_inode_watches_children(p_inode))) {
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__fsnotify_update_child_dentry_flags(p_inode);
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} else if (p_inode->i_fsnotify_mask & mask & ALL_FSNOTIFY_EVENTS) {
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struct name_snapshot name;
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/* we are notifying a parent so come up with the new mask which
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* specifies these are events which came from a child. */
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mask |= FS_EVENT_ON_CHILD;
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take_dentry_name_snapshot(&name, dentry);
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ret = fsnotify(p_inode, mask, data, data_type, &name.name, 0);
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release_dentry_name_snapshot(&name);
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}
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dput(parent);
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return ret;
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}
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EXPORT_SYMBOL_GPL(fsnotify_parent);
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static int send_to_group(struct inode *to_tell,
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__u32 mask, const void *data,
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int data_is, u32 cookie,
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const struct qstr *file_name,
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struct fsnotify_iter_info *iter_info)
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{
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struct fsnotify_group *group = NULL;
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__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
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__u32 marks_mask = 0;
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__u32 marks_ignored_mask = 0;
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struct fsnotify_mark *mark;
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int type;
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if (WARN_ON(!iter_info->report_mask))
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return 0;
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/* clear ignored on inode modification */
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if (mask & FS_MODIFY) {
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fsnotify_foreach_obj_type(type) {
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if (!fsnotify_iter_should_report_type(iter_info, type))
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continue;
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mark = iter_info->marks[type];
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if (mark &&
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!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
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mark->ignored_mask = 0;
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}
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}
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fsnotify_foreach_obj_type(type) {
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if (!fsnotify_iter_should_report_type(iter_info, type))
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continue;
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mark = iter_info->marks[type];
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/* does the object mark tell us to do something? */
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if (mark) {
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group = mark->group;
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marks_mask |= mark->mask;
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marks_ignored_mask |= mark->ignored_mask;
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}
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}
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pr_debug("%s: group=%p to_tell=%p mask=%x marks_mask=%x marks_ignored_mask=%x"
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" data=%p data_is=%d cookie=%d\n",
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__func__, group, to_tell, mask, marks_mask, marks_ignored_mask,
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data, data_is, cookie);
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if (!(test_mask & marks_mask & ~marks_ignored_mask))
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return 0;
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return group->ops->handle_event(group, to_tell, mask, data, data_is,
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file_name, cookie, iter_info);
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}
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static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
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{
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struct fsnotify_mark_connector *conn;
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struct hlist_node *node = NULL;
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conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
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if (conn)
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node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
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return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
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}
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static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
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{
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struct hlist_node *node = NULL;
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if (mark)
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node = srcu_dereference(mark->obj_list.next,
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&fsnotify_mark_srcu);
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return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
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}
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/*
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* iter_info is a multi head priority queue of marks.
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* Pick a subset of marks from queue heads, all with the
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* same group and set the report_mask for selected subset.
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* Returns the report_mask of the selected subset.
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*/
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static unsigned int fsnotify_iter_select_report_types(
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struct fsnotify_iter_info *iter_info)
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{
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struct fsnotify_group *max_prio_group = NULL;
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struct fsnotify_mark *mark;
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int type;
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/* Choose max prio group among groups of all queue heads */
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fsnotify_foreach_obj_type(type) {
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mark = iter_info->marks[type];
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if (mark &&
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fsnotify_compare_groups(max_prio_group, mark->group) > 0)
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max_prio_group = mark->group;
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}
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if (!max_prio_group)
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return 0;
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/* Set the report mask for marks from same group as max prio group */
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iter_info->report_mask = 0;
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fsnotify_foreach_obj_type(type) {
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mark = iter_info->marks[type];
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if (mark &&
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fsnotify_compare_groups(max_prio_group, mark->group) == 0)
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fsnotify_iter_set_report_type(iter_info, type);
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}
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return iter_info->report_mask;
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}
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/*
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* Pop from iter_info multi head queue, the marks that were iterated in the
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* current iteration step.
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*/
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static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
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{
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int type;
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fsnotify_foreach_obj_type(type) {
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if (fsnotify_iter_should_report_type(iter_info, type))
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iter_info->marks[type] =
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fsnotify_next_mark(iter_info->marks[type]);
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}
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}
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/*
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* This is the main call to fsnotify. The VFS calls into hook specific functions
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* in linux/fsnotify.h. Those functions then in turn call here. Here will call
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* out to all of the registered fsnotify_group. Those groups can then use the
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* notification event in whatever means they feel necessary.
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*/
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int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
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const struct qstr *file_name, u32 cookie)
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{
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const struct path *path = fsnotify_data_path(data, data_is);
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struct fsnotify_iter_info iter_info = {};
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struct super_block *sb = to_tell->i_sb;
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struct mount *mnt = NULL;
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__u32 mnt_or_sb_mask = sb->s_fsnotify_mask;
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int ret = 0;
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__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
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if (path) {
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mnt = real_mount(path->mnt);
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mnt_or_sb_mask |= mnt->mnt_fsnotify_mask;
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}
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/* An event "on child" is not intended for a mount/sb mark */
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if (mask & FS_EVENT_ON_CHILD)
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mnt_or_sb_mask = 0;
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/*
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* Optimization: srcu_read_lock() has a memory barrier which can
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* be expensive. It protects walking the *_fsnotify_marks lists.
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* However, if we do not walk the lists, we do not have to do
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* SRCU because we have no references to any objects and do not
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* need SRCU to keep them "alive".
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*/
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if (!to_tell->i_fsnotify_marks && !sb->s_fsnotify_marks &&
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(!mnt || !mnt->mnt_fsnotify_marks))
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return 0;
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/*
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* if this is a modify event we may need to clear the ignored masks
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* otherwise return if neither the inode nor the vfsmount/sb care about
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* this type of event.
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*/
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if (!(mask & FS_MODIFY) &&
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!(test_mask & (to_tell->i_fsnotify_mask | mnt_or_sb_mask)))
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return 0;
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iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
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iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
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fsnotify_first_mark(&to_tell->i_fsnotify_marks);
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iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
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fsnotify_first_mark(&sb->s_fsnotify_marks);
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if (mnt) {
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iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
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fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
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}
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/*
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* We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
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* ignore masks are properly reflected for mount/sb mark notifications.
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* That's why this traversal is so complicated...
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*/
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while (fsnotify_iter_select_report_types(&iter_info)) {
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ret = send_to_group(to_tell, mask, data, data_is, cookie,
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file_name, &iter_info);
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if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
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goto out;
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fsnotify_iter_next(&iter_info);
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}
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ret = 0;
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out:
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srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(fsnotify);
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static __init int fsnotify_init(void)
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{
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int ret;
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BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 26);
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ret = init_srcu_struct(&fsnotify_mark_srcu);
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if (ret)
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panic("initializing fsnotify_mark_srcu");
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fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
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SLAB_PANIC);
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return 0;
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}
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core_initcall(fsnotify_init);
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