WSL2-Linux-Kernel/fs/notify/vfsmount_mark.c

/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/writeback.h> /* for inode_lock */

#include <asm/atomic.h>

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

void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
{
	struct fsnotify_mark *mark, *lmark;
	struct hlist_node *pos, *n;
	LIST_HEAD(free_list);

	spin_lock(&mnt->mnt_root->d_lock);
	hlist_for_each_entry_safe(mark, pos, n, &mnt->mnt_fsnotify_marks, m.m_list) {
		list_add(&mark->m.free_m_list, &free_list);
		hlist_del_init(&mark->m.m_list);
		fsnotify_get_mark(mark);
	}
	spin_unlock(&mnt->mnt_root->d_lock);

	list_for_each_entry_safe(mark, lmark, &free_list, m.free_m_list) {
		fsnotify_destroy_mark(mark);
		fsnotify_put_mark(mark);
	}
}

/*
 * Recalculate the mask of events relevant to a given vfsmount locked.
 */
static void fsnotify_recalc_vfsmount_mask_locked(struct vfsmount *mnt)
{
	struct fsnotify_mark *mark;
	struct hlist_node *pos;
	__u32 new_mask = 0;

	assert_spin_locked(&mnt->mnt_root->d_lock);

	hlist_for_each_entry(mark, pos, &mnt->mnt_fsnotify_marks, m.m_list)
		new_mask |= mark->mask;
	mnt->mnt_fsnotify_mask = new_mask;
}

/*
 * Recalculate the mnt->mnt_fsnotify_mask, or the mask of all FS_* event types
 * any notifier is interested in hearing for this mount point
 */
void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt)
{
	spin_lock(&mnt->mnt_root->d_lock);
	fsnotify_recalc_vfsmount_mask_locked(mnt);
	spin_unlock(&mnt->mnt_root->d_lock);
}

void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
{
	struct vfsmount *mnt = mark->m.mnt;

	assert_spin_locked(&mark->lock);
	assert_spin_locked(&mark->group->mark_lock);

	spin_lock(&mnt->mnt_root->d_lock);

	hlist_del_init(&mark->m.m_list);
	mark->m.mnt = NULL;

	fsnotify_recalc_vfsmount_mask_locked(mnt);

	spin_unlock(&mnt->mnt_root->d_lock);
}

static struct fsnotify_mark *fsnotify_find_vfsmount_mark_locked(struct fsnotify_group *group,
								struct vfsmount *mnt)
{
	struct fsnotify_mark *mark;
	struct hlist_node *pos;

	assert_spin_locked(&mnt->mnt_root->d_lock);

	hlist_for_each_entry(mark, pos, &mnt->mnt_fsnotify_marks, m.m_list) {
		if (mark->group == group) {
			fsnotify_get_mark(mark);
			return mark;
		}
	}
	return NULL;
}

/*
 * given a group and vfsmount, find the mark associated with that combination.
 * if found take a reference to that mark and return it, else return NULL
 */
struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group,
						  struct vfsmount *mnt)
{
	struct fsnotify_mark *mark;

	spin_lock(&mnt->mnt_root->d_lock);
	mark = fsnotify_find_vfsmount_mark_locked(group, mnt);
	spin_unlock(&mnt->mnt_root->d_lock);

	return mark;
}

/*
 * Attach an initialized mark to a given group and vfsmount.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which groups.
 */
int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
			       struct fsnotify_group *group, struct vfsmount *mnt,
			       int allow_dups)
{
	struct fsnotify_mark *lmark = NULL;
	int ret = 0;

	mark->flags = FSNOTIFY_MARK_FLAG_VFSMOUNT;

	/*
	 * LOCKING ORDER!!!!
	 * mark->lock
	 * group->mark_lock
	 * mnt->mnt_root->d_lock
	 */
	assert_spin_locked(&mark->lock);
	assert_spin_locked(&group->mark_lock);

	spin_lock(&mnt->mnt_root->d_lock);

	if (!allow_dups)
		lmark = fsnotify_find_vfsmount_mark_locked(group, mnt);
	if (!lmark) {
		mark->m.mnt = mnt;

		hlist_add_head(&mark->m.m_list, &mnt->mnt_fsnotify_marks);

		fsnotify_recalc_vfsmount_mask_locked(mnt);
	} else {
		ret = -EEXIST;
	}

	spin_unlock(&mnt->mnt_root->d_lock);

	return ret;
}