From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Running my yearly branch profiling code, it detected a 100% wrong branch
condition in name.c for lookup_fast(). The code in question has:
status = d_revalidate(dentry, nd->flags);
if (likely(status > 0))
return dentry;
if (unlazy_child(nd, dentry, seq))
return ERR_PTR(-ECHILD);
if (unlikely(status == -ECHILD))
/* we'd been told to redo it in non-rcu mode */
status = d_revalidate(dentry, nd->flags);
If the status of the d_revalidate() is greater than zero, then the function
finishes. Otherwise, if it is an "unlazy_child" it returns with -ECHILD.
After the above two checks, the status is compared to -ECHILD, as that is
what is returned if the original d_revalidate() needed to be done in a
non-rcu mode.
Especially this path is called in a condition of:
if (nd->flags & LOOKUP_RCU) {
And most of the d_revalidate() functions have:
if (flags & LOOKUP_RCU)
return -ECHILD;
It appears that that is the only case that this if statement is triggered
on two of my machines, running in production.
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
diff --git a/fs/namei.c b/fs/namei.c
index d4a6dd772303..8dd734efae9b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1495,7 +1495,7 @@ static struct dentry *lookup_fast(struct nameidata *nd,
return dentry;
if (unlazy_child(nd, dentry, seq))
return ERR_PTR(-ECHILD);
- if (unlikely(status == -ECHILD))
+ if (likely(status == -ECHILD))
/* we'd been told to redo it in non-rcu mode */
status = d_revalidate(dentry, nd->flags);
} else {
