From 555d8f2859d5276ef2fcc1e6c0c0cef6887f4d86 Mon Sep 17 00:00:00 2001
From: Rick Macklem <rmacklem@FreeBSD.org>
Date: Mon, 1 Jul 2019 20:41:43 +0000
Subject: [PATCH] Factor out the code that does a VOP_SETATTR(size) from
 vn_truncate().

This patch factors the code in vn_truncate() that does the actual
VOP_SETATTR() of size into a separate function called vn_truncate_locked().
This will allow the NFS server and the patch that adds a
copy_file_range(2) syscall to call this function instead of duplicating
the code and carrying over changes, such as the recent r347151.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D20808
---
 sys/kern/vfs_vnops.c | 34 ++++++++++++++++++++++++----------
 sys/sys/vnode.h      |  2 ++
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index c510ea618bdd..5d54ba986408 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -1289,7 +1289,6 @@ static int
 vn_truncate(struct file *fp, off_t length, struct ucred *active_cred,
     struct thread *td)
 {
-	struct vattr vattr;
 	struct mount *mp;
 	struct vnode *vp;
 	void *rl_cookie;
@@ -1316,15 +1315,8 @@ vn_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 	if (error)
 		goto out;
 #endif
-	error = VOP_ADD_WRITECOUNT(vp, 1);
-	if (error == 0) {
-		VATTR_NULL(&vattr);
-		vattr.va_size = length;
-		if ((fp->f_flag & O_FSYNC) != 0)
-			vattr.va_vaflags |= VA_SYNC;
-		error = VOP_SETATTR(vp, &vattr, fp->f_cred);
-		VOP_ADD_WRITECOUNT_CHECKED(vp, -1);
-	}
+	error = vn_truncate_locked(vp, length, (fp->f_flag & O_FSYNC) != 0,
+	    fp->f_cred);
 out:
 	VOP_UNLOCK(vp, 0);
 	vn_finished_write(mp);
@@ -1333,6 +1325,28 @@ vn_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 	return (error);
 }
 
+/*
+ * Truncate a file that is already locked.
+ */
+int
+vn_truncate_locked(struct vnode *vp, off_t length, bool sync,
+    struct ucred *cred)
+{
+	struct vattr vattr;
+	int error;
+
+	error = VOP_ADD_WRITECOUNT(vp, 1);
+	if (error == 0) {
+		VATTR_NULL(&vattr);
+		vattr.va_size = length;
+		if (sync)
+			vattr.va_vaflags |= VA_SYNC;
+		error = VOP_SETATTR(vp, &vattr, cred);
+		VOP_ADD_WRITECOUNT_CHECKED(vp, -1);
+	}
+	return (error);
+}
+
 /*
  * File table vnode stat routine.
  */
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index cfde146f6765..92615c781bb0 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -695,6 +695,8 @@ int	vn_stat(struct vnode *vp, struct stat *sb, struct ucred *active_cred,
 int	vn_start_write(struct vnode *vp, struct mount **mpp, int flags);
 int	vn_start_secondary_write(struct vnode *vp, struct mount **mpp,
 	    int flags);
+int	vn_truncate_locked(struct vnode *vp, off_t length, bool sync,
+	    struct ucred *cred);
 int	vn_writechk(struct vnode *vp);
 int	vn_extattr_get(struct vnode *vp, int ioflg, int attrnamespace,
 	    const char *attrname, int *buflen, char *buf, struct thread *td);