From 7ab7d4f0197fd2c2abc76ad22e90665847ed47cd Mon Sep 17 00:00:00 2001
From: kib <kib@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Wed, 18 May 2016 11:58:16 +0000
Subject: [PATCH] MFC r299412: Add vfs_hash_ref(9) function, which finds a
 vnode by the hash value and returns it referenced.

git-svn-id: svn://svn.freebsd.org/base/stable/10@300140 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/kern/vfs_hash.c | 30 ++++++++++++++++++++++++++++++
 sys/sys/vnode.h     |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/sys/kern/vfs_hash.c b/sys/kern/vfs_hash.c
index b7029236d..d2fbbd697 100644
--- a/sys/kern/vfs_hash.c
+++ b/sys/kern/vfs_hash.c
@@ -102,6 +102,36 @@ vfs_hash_get(const struct mount *mp, u_int hash, int flags, struct thread *td,
 	}
 }
 
+void
+vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
+    struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
+{
+	struct vnode *vp;
+
+	while (1) {
+		mtx_lock(&vfs_hash_mtx);
+		LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
+			if (vp->v_hash != hash)
+				continue;
+			if (vp->v_mount != mp)
+				continue;
+			if (fn != NULL && fn(vp, arg))
+				continue;
+			vhold(vp);
+			mtx_unlock(&vfs_hash_mtx);
+			vref(vp);
+			vdrop(vp);
+			*vpp = vp;
+			return;
+		}
+		if (vp == NULL) {
+			mtx_unlock(&vfs_hash_mtx);
+			*vpp = NULL;
+			return;
+		}
+	}
+}
+
 void
 vfs_hash_remove(struct vnode *vp)
 {
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index ea75d73a0..d3d79aba7 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -849,6 +849,8 @@ int vfs_hash_get(const struct mount *mp, u_int hash, int flags,
 u_int vfs_hash_index(struct vnode *vp);
 int vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td,
     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg);
+void vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
+    struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg);
 void vfs_hash_rehash(struct vnode *vp, u_int hash);
 void vfs_hash_remove(struct vnode *vp);
 
-- 
2.45.0