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![Eric Paris](/assets/img/avatar_default.png)
Currently reading the inode->i_fsnotify_marks or vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the read and the write side. This patch protects the read side of those lists with a new single srcu. Signed-off-by: Eric Paris <eparis@redhat.com>
307 lines
8.7 KiB
C
307 lines
8.7 KiB
C
/*
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* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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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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* 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(&dcache_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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list_for_each_entry(alias, &inode->i_dentry, 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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list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
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if (!child->d_inode)
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continue;
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spin_lock(&child->d_lock);
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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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}
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spin_unlock(&dcache_lock);
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}
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/* Notify this dentry's parent about a child's events. */
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void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask)
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{
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struct dentry *parent;
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struct inode *p_inode;
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bool send = false;
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bool should_update_children = false;
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if (!dentry)
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dentry = file->f_path.dentry;
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if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
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return;
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spin_lock(&dentry->d_lock);
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parent = dentry->d_parent;
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p_inode = parent->d_inode;
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if (fsnotify_inode_watches_children(p_inode)) {
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if (p_inode->i_fsnotify_mask & mask) {
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dget(parent);
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send = true;
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}
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} else {
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/*
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* The parent doesn't care about events on it's children but
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* at least one child thought it did. We need to run all the
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* children and update their d_flags to let them know p_inode
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* doesn't care about them any more.
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*/
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dget(parent);
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should_update_children = true;
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}
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spin_unlock(&dentry->d_lock);
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if (send) {
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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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if (file)
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fsnotify(p_inode, mask, file, FSNOTIFY_EVENT_FILE,
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dentry->d_name.name, 0);
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else
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fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
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dentry->d_name.name, 0);
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dput(parent);
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}
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if (unlikely(should_update_children)) {
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__fsnotify_update_child_dentry_flags(p_inode);
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dput(parent);
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}
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}
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EXPORT_SYMBOL_GPL(__fsnotify_parent);
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void __fsnotify_flush_ignored_mask(struct inode *inode, void *data, int data_is)
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{
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struct fsnotify_mark *mark;
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struct hlist_node *node;
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int idx;
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idx = srcu_read_lock(&fsnotify_mark_srcu);
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if (!hlist_empty(&inode->i_fsnotify_marks)) {
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hlist_for_each_entry_rcu(mark, node, &inode->i_fsnotify_marks, i.i_list) {
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if (!(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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if (data_is == FSNOTIFY_EVENT_FILE) {
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struct vfsmount *mnt;
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mnt = ((struct file *)data)->f_path.mnt;
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if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
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hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
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if (!(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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}
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srcu_read_unlock(&fsnotify_mark_srcu, idx);
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}
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static int send_to_group(struct fsnotify_group *group, struct inode *to_tell,
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struct vfsmount *mnt, __u32 mask, void *data,
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int data_is, u32 cookie, const unsigned char *file_name,
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struct fsnotify_event **event)
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{
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pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_is=%d"
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" cookie=%d event=%p\n", __func__, group, to_tell, mnt,
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mask, data, data_is, cookie, *event);
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if (!group->ops->should_send_event(group, to_tell, mnt, mask,
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data, data_is))
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return 0;
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if (!*event) {
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*event = fsnotify_create_event(to_tell, mask, data,
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data_is, file_name,
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cookie, GFP_KERNEL);
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if (!*event)
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return -ENOMEM;
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}
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return group->ops->handle_event(group, *event);
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}
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static bool needed_by_vfsmount(__u32 test_mask, struct vfsmount *mnt)
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{
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if (!mnt)
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return false;
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return (test_mask & mnt->mnt_fsnotify_mask);
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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, void *data, int data_is,
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const unsigned char *file_name, u32 cookie)
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{
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struct fsnotify_mark *mark;
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struct fsnotify_group *group;
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struct fsnotify_event *event = NULL;
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struct hlist_node *node;
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struct vfsmount *mnt = NULL;
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int idx, ret = 0;
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/* global tests shouldn't care about events on child only the specific event */
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__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
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/* if no fsnotify listeners, nothing to do */
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if (list_empty(&fsnotify_inode_groups) &&
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list_empty(&fsnotify_vfsmount_groups))
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return 0;
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if (mask & FS_MODIFY)
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__fsnotify_flush_ignored_mask(to_tell, data, data_is);
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/* if none of the directed listeners or vfsmount listeners care */
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if (!(test_mask & fsnotify_inode_mask) &&
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!(test_mask & fsnotify_vfsmount_mask))
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return 0;
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if (data_is == FSNOTIFY_EVENT_FILE)
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mnt = ((struct file *)data)->f_path.mnt;
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/* if this inode's directed listeners don't care and nothing on the vfsmount
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* listeners list cares, nothing to do */
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if (!(test_mask & to_tell->i_fsnotify_mask) &&
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!needed_by_vfsmount(test_mask, mnt))
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return 0;
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idx = srcu_read_lock(&fsnotify_mark_srcu);
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if (test_mask & to_tell->i_fsnotify_mask) {
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hlist_for_each_entry_rcu(mark, node, &to_tell->i_fsnotify_marks, i.i_list) {
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pr_debug("%s: inode_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
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__func__, mark, mark->mask, mark->ignored_mask);
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if (test_mask & mark->mask & ~mark->ignored_mask) {
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group = mark->group;
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if (!group)
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continue;
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ret = send_to_group(group, to_tell, NULL, mask,
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data, data_is, cookie, file_name,
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&event);
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if (ret)
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goto out;
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}
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}
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}
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if (mnt && (test_mask & mnt->mnt_fsnotify_mask)) {
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hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
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pr_debug("%s: mnt_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
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__func__, mark, mark->mask, mark->ignored_mask);
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if (test_mask & mark->mask & ~mark->ignored_mask) {
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group = mark->group;
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if (!group)
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continue;
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ret = send_to_group(group, to_tell, mnt, mask,
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data, data_is, cookie, file_name,
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&event);
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if (ret)
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goto out;
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}
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}
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}
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out:
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srcu_read_unlock(&fsnotify_mark_srcu, idx);
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/*
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* fsnotify_create_event() took a reference so the event can't be cleaned
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* up while we are still trying to add it to lists, drop that one.
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*/
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if (event)
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fsnotify_put_event(event);
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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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BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
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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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return 0;
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}
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core_initcall(fsnotify_init);
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