path: root/fs/notify/fsnotify.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 */

#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/srcu.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

/*
 * Clear all of the marks on an inode when it is being evicted from core
 */
void __fsnotify_inode_delete(struct inode *inode)
{
	fsnotify_clear_marks_by_inode(inode);
}
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);

void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{
	fsnotify_clear_marks_by_mount(mnt);
}

/**
 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 * @sb: superblock being unmounted.
 *
 * Called during unmount with no locks held, so needs to be safe against
 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
 */
static void fsnotify_unmount_inodes(struct super_block *sb)
{
	struct inode *inode, *iput_inode = NULL;

	spin_lock(&sb->s_inode_list_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
		/*
		 * We cannot __iget() an inode in state I_FREEING,
		 * I_WILL_FREE, or I_NEW which is fine because by that point
		 * the inode cannot have any associated watches.
		 */
		spin_lock(&inode->i_lock);
		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
			spin_unlock(&inode->i_lock);
			continue;
		}

		/*
		 * If i_count is zero, the inode cannot have any watches and
		 * doing an __iget/iput with SB_ACTIVE clear would actually
		 * evict all inodes with zero i_count from icache which is
		 * unnecessarily violent and may in fact be illegal to do.
		 * However, we should have been called /after/ evict_inodes
		 * removed all zero refcount inodes, in any case.  Test to
		 * be sure.
		 */
		if (!atomic_read(&inode->i_count)) {
			spin_unlock(&inode->i_lock);
			continue;
		}

		__iget(inode);
		spin_unlock(&inode->i_lock);
		spin_unlock(&sb->s_inode_list_lock);

		if (iput_inode)
			iput(iput_inode);

		/* for each watch, send FS_UNMOUNT and then remove it */
		fsnotify_inode(inode, FS_UNMOUNT);

		fsnotify_inode_delete(inode);

		iput_inode = inode;

		cond_resched();
		spin_lock(&sb->s_inode_list_lock);
	}
	spin_unlock(&sb->s_inode_list_lock);

	if (iput_inode)
		iput(iput_inode);
	/* Wait for outstanding inode references from connectors */
	wait_var_event(&sb->s_fsnotify_inode_refs,
		       !atomic_long_read(&sb->s_fsnotify_inode_refs));
}

void fsnotify_sb_delete(struct super_block *sb)
{
	fsnotify_unmount_inodes(sb);
	fsnotify_clear_marks_by_sb(sb);
}

/*
 * Given an inode, first check if we care what happens to our children.  Inotify
 * and dnotify both tell their parents about events.  If we care about any event
 * on a child we run all of our children and set a dentry flag saying that the
 * parent cares.  Thus when an event happens on a child it can quickly tell if
 * if there is a need to find a parent and send the event to the parent.
 */
void __fsnotify_update_child_dentry_flags(struct inode *inode)
{
	struct dentry *alias;
	int watched;

	if (!S_ISDIR(inode->i_mode))
		return;

	/* determine if the children should tell inode about their events */
	watched = fsnotify_inode_watches_children(inode);

	spin_lock(&inode->i_lock);
	/* run all of the dentries associated with this inode.  Since this is a
	 * directory, there damn well better only be one item on this list */
	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
		struct dentry *child;

		/* run all of the children of the original inode and fix their
		 * d_flags to indicate parental interest (their parent is the
		 * original inode) */
		spin_lock(&alias->d_lock);
		list_for_each_entry(child, &alias->d_subdirs, d_child) {
			if (!child->d_inode)
				continue;

			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
			if (watched)
				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
			else
				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
			spin_unlock(&child->d_lock);
		}
		spin_unlock(&alias->d_lock);
	}
	spin_unlock(&inode->i_lock);
}

/* Are inode/sb/mount interested in parent and name info with this event? */
static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
					__u32 mask)
{
	__u32 marks_mask = 0;

	/* We only send parent/name to inode/sb/mount for events on non-dir */
	if (mask & FS_ISDIR)
		return false;

	/*
	 * All events that are possible on child can also may be reported with
	 * parent/name info to inode/sb/mount.  Otherwise, a watching parent
	 * could result in events reported with unexpected name info to sb/mount.
	 */
	BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);

	/* Did either inode/sb/mount subscribe for events with parent/name? */
	marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
	marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
	if (mnt)
		marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);

	/* Did they subscribe for this event with parent/name info? */
	return mask & marks_mask;
}

/*
 * Notify this dentry's parent about a child's events with child name info
 * if parent is watching or if inode/sb/mount are interested in events with
 * parent and name info.
 *
 * Notify only the child without name info if parent is not watching and
 * inode/sb/mount are not interested in events with parent and name info.
 */
int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
		      int data_type)
{
	const struct path *path = fsnotify_data_path(data, data_type);
	struct mount *mnt = path ? real_mount(path->mnt) : NULL;
	struct inode *inode = d_inode(dentry);
	struct dentry *parent;
	bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
	bool parent_needed, parent_interested;
	__u32 p_mask;
	struct inode *p_inode = NULL;
	struct name_snapshot name;
	struct qstr *file_name = NULL;
	int ret = 0;

	/*
	 * Do inode/sb/mount care about parent and name info on non-dir?
	 * Do they care about any event at all?
	 */
	if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
	    (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
		return 0;

	parent = NULL;
	parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
	if (!parent_watched && !parent_needed)
		goto notify;

	/* Does parent inode care about events on children? */
	parent = dget_parent(dentry);
	p_inode = parent->d_inode;
	p_mask = fsnotify_inode_watches_children(p_inode);
	if (unlikely(parent_watched && !p_mask))
		__fsnotify_update_child_dentry_flags(p_inode);

	/*
	 * Include parent/name in notification either if some notification
	 * groups require parent info or the parent is interested in this event.
	 */
	parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
	if (parent_needed || parent_interested) {
		/* When notifying parent, child should be passed as data */
		WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));

		/* Notify both parent and child with child name info */
		take_dentry_name_snapshot(&name, dentry);
		file_name = &name.name;
		if (parent_interested)
			mask |= FS_EVENT_ON_CHILD;
	}

notify:
	ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);

	if (file_name)
		release_dentry_name_snapshot(&name);
	dput(parent);

	return ret;
}
EXPORT_SYMBOL_GPL(__fsnotify_parent);

static int fsnotify_handle_inode_event(struct fsnotify_group *group,
				       struct fsnotify_mark *inode_mark,
				       u32 mask, const void *data, int data_type,
				       struct inode *dir, const struct qstr *name,
				       u32 cookie)
{
	const struct path *path = fsnotify_data_path(data, data_type);
	struct inode *inode = fsnotify_data_inode(data, data_type);
	const struct fsnotify_ops *ops = group->ops;

	if (WARN_ON_ONCE(!ops->handle_inode_event))
		return 0;

	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
	    path && d_unlinked