From e17e01bd0e4a528fff69bff8faf7045d4d619aae Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjguzik@gmail.com>
Date: Mon, 28 Dec 2020 08:46:02 +0100
Subject: [PATCH] cache: refactor dot handling

Tested by:	pho
---
 sys/kern/vfs_cache.c | 51 ++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index d5e5e6e3d01..22a5b54b280 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -3746,6 +3746,7 @@ _Static_assert((CACHE_FPL_SUPPORTED_CN_FLAGS & CACHE_FPL_INTERNAL_CN_FLAGS) == 0
     "supported and internal flags overlap");
 
 static bool cache_fplookup_is_mp(struct cache_fpl *fpl);
+static int cache_fplookup_cross_mount(struct cache_fpl *fpl);
 
 static bool
 cache_fpl_islastcn(struct nameidata *ndp)
@@ -4392,6 +4393,7 @@ cache_fplookup_noentry(struct cache_fpl *fpl)
 static int __noinline
 cache_fplookup_dot(struct cache_fpl *fpl)
 {
+	int error;
 
 	MPASS(!seqc_in_modify(fpl->dvp_seqc));
 	/*
@@ -4401,6 +4403,12 @@ cache_fplookup_dot(struct cache_fpl *fpl)
 	 */
 	fpl->tvp = fpl->dvp;
 	fpl->tvp_seqc = fpl->dvp_seqc;
+	if (cache_fplookup_is_mp(fpl)) {
+		error = cache_fplookup_cross_mount(fpl);
+		if (__predict_false(error != 0)) {
+			return (error);
+		}
+	}
 
 	counter_u64_add(dothits, 1);
 	SDT_PROBE3(vfs, namecache, lookup, hit, fpl->dvp, ".", fpl->dvp);
@@ -4421,6 +4429,8 @@ cache_fplookup_dotdot(struct cache_fpl *fpl)
 	cnp = fpl->cnp;
 	dvp = fpl->dvp;
 
+	MPASS(cache_fpl_isdotdot(cnp));
+
 	/*
 	 * XXX this is racy the same way regular lookup is
 	 */
@@ -4520,14 +4530,22 @@ cache_fplookup_next(struct cache_fpl *fpl)
 	struct vnode *dvp, *tvp;
 	u_char nc_flag;
 	uint32_t hash;
+	int error;
 
 	cnp = fpl->cnp;
 	dvp = fpl->dvp;
 
-	if (__predict_false(cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.')) {
-		return (cache_fplookup_dot(fpl));
+	if (__predict_false(cnp->cn_nameptr[0] == '.')) {
+		if (cnp->cn_namelen == 1) {
+			return (cache_fplookup_dot(fpl));
+		}
+		if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
+			return (cache_fplookup_dotdot(fpl));
+		}
 	}
 
+	MPASS(!cache_fpl_isdotdot(cnp));
+
 	hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
 
 	CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
@@ -4560,6 +4578,13 @@ cache_fplookup_next(struct cache_fpl *fpl)
 		return (cache_fpl_partial(fpl));
 	}
 
+	if (cache_fplookup_is_mp(fpl)) {
+		error = cache_fplookup_cross_mount(fpl);
+		if (__predict_false(error != 0)) {
+			return (error);
+		}
+	}
+
 	counter_u64_add(numposhits, 1);
 	SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, tvp);
 	return (0);
@@ -4973,25 +4998,9 @@ cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
 			break;
 		}
 
-		if (__predict_false(cache_fpl_isdotdot(cnp))) {
-			error = cache_fplookup_dotdot(fpl);
-			if (__predict_false(cache_fpl_terminated(fpl))) {
-				break;
-			}
-		} else {
-			error = cache_fplookup_next(fpl);
-			if (__predict_false(cache_fpl_terminated(fpl))) {
-				break;
-			}
-
-			VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
-
-			if (cache_fplookup_is_mp(fpl)) {
-				error = cache_fplookup_cross_mount(fpl);
-				if (__predict_false(error != 0)) {
-					break;
-				}
-			}
+		error = cache_fplookup_next(fpl);
+		if (__predict_false(cache_fpl_terminated(fpl))) {
+			break;
 		}
 
 		VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
-- 
2.45.0