Commit 6e180327 authored by Al Viro's avatar Al Viro
Browse files

namei: move clearing LOOKUP_RCU towards rcu_read_unlock() 



try_to_unlazy()/try_to_unlazy_next() drop LOOKUP_RCU in the
very beginning and do rcu_read_unlock() only at the very end.
However, nothing done in between even looks at the flag in
question; might as well clear it at the same time we unlock.

Note that try_to_unlazy_next() used to call legitimize_mnt(),
which might drop/regain rcu_read_lock() in some cases.  This
is no longer true, so we really have rcu_read_lock() held
all along until the end.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 7e4745a0

fs/namei.c

+12 −9
Original line number Diff line number Diff line
@@ -665,6 +665,12 @@ static void drop_links(struct nameidata *nd) 
	}

}



static void leave_rcu(struct nameidata *nd)

{

	nd->flags &= ~LOOKUP_RCU;

	rcu_read_unlock();

}



static void terminate_walk(struct nameidata *nd)

{

	drop_links(nd);
@@ -678,8 +684,7 @@ static void terminate_walk(struct nameidata *nd) 
			nd->state &= ~ND_ROOT_GRABBED;

		}

	} else {

		nd->flags &= ~LOOKUP_RCU;

		rcu_read_unlock();

		leave_rcu(nd);

	}

	nd->depth = 0;

	nd->path.mnt = NULL;
@@ -765,14 +770,13 @@ static bool try_to_unlazy(struct nameidata *nd) 


	BUG_ON(!(nd->flags & LOOKUP_RCU));



	nd->flags &= ~LOOKUP_RCU;

	if (unlikely(!legitimize_links(nd)))

		goto out1;

	if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))

		goto out;

	if (unlikely(!legitimize_root(nd)))

		goto out;

	rcu_read_unlock();

	leave_rcu(nd);

	BUG_ON(nd->inode != parent->d_inode);

	return true;
@@ -780,7 +784,7 @@ static bool try_to_unlazy(struct nameidata *nd) 
	nd->path.mnt = NULL;

	nd->path.dentry = NULL;

out:

	rcu_read_unlock();

	leave_rcu(nd);

	return false;

}
@@ -802,7 +806,6 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi 
	int res;

	BUG_ON(!(nd->flags & LOOKUP_RCU));



	nd->flags &= ~LOOKUP_RCU;

	if (unlikely(!legitimize_links(nd)))

		goto out2;

	res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
@@ -831,7 +834,7 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi 
	 */

	if (unlikely(!legitimize_root(nd)))

		goto out_dput;

	rcu_read_unlock();

	leave_rcu(nd);

	return true;



out2:
@@ -839,10 +842,10 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi 
out1:

	nd->path.dentry = NULL;

out:

	rcu_read_unlock();

	leave_rcu(nd);

	return false;

out_dput:

	rcu_read_unlock();

	leave_rcu(nd);

	dput(dentry);

	return false;

}