git: 7220a10b5b34 - main - cache: predict on no spurious slashes in cache_fpl_handle_root

[Mateusz Guzik]

The branch main has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=7220a10b5b343f0528612c62072f80458076a061

commit 7220a10b5b343f0528612c62072f80458076a061
Author:     Mateusz Guzik <mjg at FreeBSD.org>
AuthorDate: 2021-01-01 02:25:19 +0000
Commit:     Mateusz Guzik <mjg at FreeBSD.org>
CommitDate: 2021-01-03 06:50:06 +0000

    cache: predict on no spurious slashes in cache_fpl_handle_root
    
    This is a step towards speculatively not handling them.
---
 sys/kern/vfs_cache.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index b4882079790d..396969bb10ec 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -3623,9 +3623,15 @@ cache_fpl_handle_root(struct cache_fpl *fpl)
 	ndp = fpl->ndp;
 	cnp = fpl->cnp;
 
-	while (*(cnp->cn_nameptr) == '/') {
-		cnp->cn_nameptr++;
-		ndp->ni_pathlen--;
+	MPASS(*(cnp->cn_nameptr) == '/');
+	cnp->cn_nameptr++;
+	ndp->ni_pathlen--;
+
+	if (__predict_false(*(cnp->cn_nameptr) == '/')) {
+		do {
+			cnp->cn_nameptr++;
+			ndp->ni_pathlen--;
+		} while (*(cnp->cn_nameptr) == '/');
 	}
 
 	return (ndp->ni_rootdir);