git: 09f925b57aeb - main - nullfs: Slightly reduce contention by reducing concurrent sections

The branch main has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=09f925b57aeb171318a9d54df500bf22b4cdd986

commit 09f925b57aeb171318a9d54df500bf22b4cdd986
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2025-10-06 13:22:13 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2025-10-06 15:21:45 +0000

    nullfs: Slightly reduce contention by reducing concurrent sections
    
    In null_lock_prep_with_smr(), initialize 'lvp' outside of the
    SMR-protected section.
    
    In null_lock(), if after locking the lower vnode we notice that we have
    been reclaimed, we have to unlock the lower vnode and then relock our
    own now that the lock isn't shared anymore.  Call VOP_UNLOCK() on the
    lower vnode as soon as this condition is known.
    
    This applies comments from D38761, one of which was missed and the other
    added too late.
    
    Reviewed by:    kib
    MFC with:       641a58239520 ("nullfs: avoid the interlock in null_lock with smr")
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D52935
---
 sys/fs/nullfs/null_vnops.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c
index 375b6aa27531..ec8a6b10b13f 100644
--- a/sys/fs/nullfs/null_vnops.c
+++ b/sys/fs/nullfs/null_vnops.c
@@ -788,10 +788,10 @@ null_lock_prep_with_smr(struct vop_lock1_args *ap)
 	struct null_node *nn;
 	struct vnode *lvp;
 
-	vfs_smr_enter();
-
 	lvp = NULL;
 
+	vfs_smr_enter();
+
 	nn = VTONULL_SMR(ap->a_vp);
 	if (__predict_true(nn != NULL)) {
 		lvp = nn->null_lowervp;
@@ -855,6 +855,8 @@ null_lock(struct vop_lock1_args *ap)
 	 * case by reacquiring correct lock in requested mode.
 	 */
 	if (VTONULL(ap->a_vp) == NULL && error == 0) {
+		VOP_UNLOCK(lvp);
+
 		flags = ap->a_flags;
 		ap->a_flags &= ~LK_TYPE_MASK;
 		switch (flags & LK_TYPE_MASK) {
@@ -869,7 +871,6 @@ null_lock(struct vop_lock1_args *ap)
 			panic("Unsupported lock request %d\n",
 			    flags);
 		}
-		VOP_UNLOCK(lvp);
 		error = vop_stdlock(ap);
 	}
 	vdrop(lvp);