From 6e180327153071281dbbf6a16759e49862debdca Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 6 Jul 2022 12:40:31 -0400 Subject: 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: Al Viro --- fs/namei.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index e864d5b9eeac..4b7a2147c207 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -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 @@ out1: 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 @@ out2: 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; } -- cgit v1.2.3