git: 4bddcc418971 - stable/13 - vfs: stabilize freevnodes_old

The branch stable/13 has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=4bddcc418971bf21fb5e760248045f8a222a9a80

commit 4bddcc418971bf21fb5e760248045f8a222a9a80
Author:     Mateusz Guzik <mjg@FreeBSD.org>
AuthorDate: 2023-09-16 15:41:12 +0000
Commit:     Mateusz Guzik <mjg@FreeBSD.org>
CommitDate: 2023-10-04 12:05:58 +0000

    vfs: stabilize freevnodes_old
    
    In face of parallel callers.
    
    (cherry picked from commit ef89b78bb1f60484cc743fa590d623ad896ca8e9)
---
 sys/kern/vfs_subr.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index b125438923bf..37554858173f 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1545,21 +1545,22 @@ vfs_freevnodes_dec(void)
 static u_long
 vnlru_read_freevnodes(void)
 {
-	long slop, rfreevnodes;
+	long slop, rfreevnodes, rfreevnodes_old;
 	int cpu;
 
 	rfreevnodes = atomic_load_long(&freevnodes);
+	rfreevnodes_old = atomic_load_long(&freevnodes_old);
 
-	if (rfreevnodes > freevnodes_old)
-		slop = rfreevnodes - freevnodes_old;
+	if (rfreevnodes > rfreevnodes_old)
+		slop = rfreevnodes - rfreevnodes_old;
 	else
-		slop = freevnodes_old - rfreevnodes;
+		slop = rfreevnodes_old - rfreevnodes;
 	if (slop < VNLRU_FREEVNODES_SLOP)
 		return (rfreevnodes >= 0 ? rfreevnodes : 0);
-	freevnodes_old = rfreevnodes;
 	CPU_FOREACH(cpu) {
-		freevnodes_old += cpuid_to_pcpu[cpu]->pc_vfs_freevnodes;
+		rfreevnodes += cpuid_to_pcpu[cpu]->pc_vfs_freevnodes;
 	}
+	atomic_store_long(&freevnodes_old, rfreevnodes);
 	return (freevnodes_old >= 0 ? freevnodes_old : 0);
 }