linux-kernel - [PATCH] namei: Remove unlikely annotation for revalidate check in lookup

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Date:   Mon, 6 Feb 2017 17:17:35 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH] namei: Remove unlikely annotation for revalidate check in
 lookup_fast()

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

The likely/unlikely profiler showed that the unlikely around the
dentry->d_flags & DCACHE_OP_REVALIDATE was wrong 95% of the time. Adding
trace_printk()s, it revealed that the dentry ops had hooks to:

 kernfs_dop_revalidate
 pid_revalidate
 proc_sys_revalidate
 tid_fd_revalidate

As tools today now access files that have these operations often, it's best
just to remove the annotation, as it is more dependent on use cases and not
normal mode of operation if it will be true or not.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 fs/namei.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index ad74877..23ce3e8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1599,7 +1599,7 @@ static int lookup_fast(struct nameidata *nd,
 		dentry = __d_lookup(parent, &nd->last);
 		if (unlikely(!dentry))
 			return 0;
-		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
+		if (dentry->d_flags & DCACHE_OP_REVALIDATE)
 			status = d_revalidate(dentry, nd->flags);
 	}
 	if (unlikely(status <= 0)) {
-- 
2.9.3