Commit ff17fa56 authored by Al Viro's avatar Al Viro
Browse files

d_invalidate(): unhash immediately 



Once that is done, we can just hunt mountpoints down one by one;
no new mountpoints can be added from now on, so we don't need
anything tricky in finish() callback, etc.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 60cc43fc

fs/dcache.c

+16 −46
Original line number Diff line number Diff line
@@ -1542,78 +1542,48 @@ void shrink_dcache_for_umount(struct super_block *sb) 
	}

}



struct detach_data {

	struct select_data select;

	struct dentry *mountpoint;

};

static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)

static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)

{

	struct detach_data *data = _data;



	struct dentry **victim = _data;

	if (d_mountpoint(dentry)) {

		__dget_dlock(dentry);

		data->mountpoint = dentry;

		*victim = dentry;

		return D_WALK_QUIT;

	}



	return select_collect(&data->select, dentry);

}



static void check_and_drop(void *_data)

{

	struct detach_data *data = _data;



	if (!data->mountpoint && list_empty(&data->select.dispose))

		__d_drop(data->select.start);

	return D_WALK_CONTINUE;

}



/**

 * d_invalidate - detach submounts, prune dcache, and drop

 * @dentry: dentry to invalidate (aka detach, prune and drop)

 *

 * no dcache lock.

 *

 * The final d_drop is done as an atomic operation relative to

 * rename_lock ensuring there are no races with d_set_mounted.  This

 * ensures there are no unhashed dentries on the path to a mountpoint.

 */

void d_invalidate(struct dentry *dentry)

{

	/*

	 * If it's already been dropped, return OK.

	 */

	bool had_submounts = false;

	spin_lock(&dentry->d_lock);

	if (d_unhashed(dentry)) {

		spin_unlock(&dentry->d_lock);

		return;

	}

	__d_drop(dentry);

	spin_unlock(&dentry->d_lock);



	/* Negative dentries can be dropped without further checks */

	if (!dentry->d_inode) {

		d_drop(dentry);

	if (!dentry->d_inode)

		return;

	}



	shrink_dcache_parent(dentry);

	for (;;) {

		struct detach_data data;



		data.mountpoint = NULL;

		INIT_LIST_HEAD(&data.select.dispose);

		data.select.start = dentry;

		data.select.found = 0;



		d_walk(dentry, &data, detach_and_collect, check_and_drop);



		if (!list_empty(&data.select.dispose))

			shrink_dentry_list(&data.select.dispose);

		else if (!data.mountpoint)

		struct dentry *victim = NULL;

		d_walk(dentry, &victim, find_submount, NULL);

		if (!victim) {

			if (had_submounts)

				shrink_dcache_parent(dentry);

			return;



		if (data.mountpoint) {

			detach_mounts(data.mountpoint);

			dput(data.mountpoint);

		}

		had_submounts = true;

		detach_mounts(victim);

		dput(victim);

	}

}

EXPORT_SYMBOL(d_invalidate);