usb: gadget: f_mtp: Avoid race between mtp_read and mtp_function_disable

[GitHub/exynos8895/android_kernel_samsung_universal8895.git] / fs / notify / inode_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/mutex.h>
#include <linux/spinlock.h>

#include <linux/atomic.h>

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

#include "../internal.h"

/*
 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
 * any notifier is interested in hearing for this inode.
 */
void fsnotify_recalc_inode_mask(struct inode *inode)
{
	spin_lock(&inode->i_lock);
	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
	spin_unlock(&inode->i_lock);

	__fsnotify_update_child_dentry_flags(inode);
}

void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
	struct inode *inode = mark->inode;

	BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
	assert_spin_locked(&mark->lock);

	spin_lock(&inode->i_lock);

	hlist_del_init_rcu(&mark->obj_list);
	mark->inode = NULL;

	/*
	 * this mark is now off the inode->i_fsnotify_marks list and we
	 * hold the inode->i_lock, so this is the perfect time to update the
	 * inode->i_fsnotify_mask
	 */
	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
	spin_unlock(&inode->i_lock);
}

/*
 * Given a group clear all of the inode marks associated with that group.
 */
void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
{
	fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
}

/*
 * given a group and inode, 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_inode_mark(struct fsnotify_group *group,
					       struct inode *inode)
{
	struct fsnotify_mark *mark;

	spin_lock(&inode->i_lock);
	mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
	spin_unlock(&inode->i_lock);

	return mark;
}

/*
 * If we are setting a mark mask on an inode mark we should pin the inode
 * in memory.
 */
void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
					 __u32 mask)
{
	struct inode *inode;

	assert_spin_locked(&mark->lock);

	if (mask &&
	    mark->inode &&
	    !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
		mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
		inode = igrab(mark->inode);
		/*
		 * we shouldn't be able to get here if the inode wasn't
		 * already safely held in memory.  But bug in case it
		 * ever is wrong.
		 */
		BUG_ON(!inode);
	}
}

/*
 * Attach an initialized mark to a given inode.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which group and for which inodes.  These
 * marks are ordered according to priority, highest number first, and then by
 * the group's location in memory.
 */
int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
			    struct fsnotify_group *group, struct inode *inode,
			    int allow_dups)
{
	int ret;

	mark->flags |= FSNOTIFY_MARK_FLAG_INODE;

	BUG_ON(!mutex_is_locked(&group->mark_mutex));
	assert_spin_locked(&mark->lock);

	spin_lock(&inode->i_lock);
	mark->inode = inode;
	ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
				     allow_dups);
	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
	spin_unlock(&inode->i_lock);

	return ret;
}

/**
 * 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.
 */
void fsnotify_unmount_inodes(struct super_block *sb)
{
	struct inode *inode, *next_i, *need_iput = NULL;

	spin_lock(&sb->s_inode_list_lock);
	list_for_each_entry_safe(inode, next_i, &sb->s_inodes, i_sb_list) {
		struct inode *need_iput_tmp;

		/*
		 * 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 MS_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.
		 */
		if (!atomic_read(&inode->i_count)) {
			spin_unlock(&inode->i_lock);
			continue;
		}

		need_iput_tmp = need_iput;
		need_iput = NULL;

		/* In case fsnotify_inode_delete() drops a reference. */
		if (inode != need_iput_tmp)
			__iget(inode);
		else
			need_iput_tmp = NULL;
		spin_unlock(&inode->i_lock);

		/* In case the dropping of a reference would nuke next_i. */
		while (&next_i->i_sb_list != &sb->s_inodes) {
			spin_lock(&next_i->i_lock);
			if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
						atomic_read(&next_i->i_count)) {
				__iget(next_i);
				need_iput = next_i;
				spin_unlock(&next_i->i_lock);
				break;
			}
			spin_unlock(&next_i->i_lock);
			next_i = list_entry(next_i->i_sb_list.next,
						struct inode, i_sb_list);
		}

		/*
		 * We can safely drop s_inode_list_lock here because either
		 * we actually hold references on both inode and next_i or
		 * end of list.  Also no new inodes will be added since the
		 * umount has begun.
		 */
		spin_unlock(&sb->s_inode_list_lock);

		if (need_iput_tmp)
			iput(need_iput_tmp);

		/* for each watch, send FS_UNMOUNT and then remove it */
		fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);

		fsnotify_inode_delete(inode);

		iput(inode);

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