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Date:      Sat, 28 Aug 2010 08:57:15 +0000 (UTC)
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r211930 - in head/sys: kern sys
Message-ID:  <201008280857.o7S8vFVx024826@svn.freebsd.org>
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Author: pjd
Date: Sat Aug 28 08:57:15 2010
New Revision: 211930
URL: http://svn.freebsd.org/changeset/base/211930

Log:
  There is a bug in vfs_allocate_syncvnode() failure handling in mount code.
  Actually it is hard to properly handle such a failure, especially in MNT_UPDATE
  case. The only reason for the vfs_allocate_syncvnode() function to fail is
  getnewvnode() failure. Fortunately it is impossible for current implementation
  of getnewvnode() to fail, so we can assert this and make
  vfs_allocate_syncvnode() void. This in turn free us from handling its failures
  in the mount code.
  
  Reviewed by:	kib
  MFC after:	1 month

Modified:
  head/sys/kern/vfs_mount.c
  head/sys/kern/vfs_subr.c
  head/sys/sys/mount.h

Modified: head/sys/kern/vfs_mount.c
==============================================================================
--- head/sys/kern/vfs_mount.c	Sat Aug 28 08:39:37 2010	(r211929)
+++ head/sys/kern/vfs_mount.c	Sat Aug 28 08:57:15 2010	(r211930)
@@ -1036,7 +1036,7 @@ vfs_domount(
 		MNT_IUNLOCK(mp);
 		if ((mp->mnt_flag & MNT_RDONLY) == 0) {
 			if (mp->mnt_syncer == NULL)
-				error = vfs_allocate_syncvnode(mp);
+				vfs_allocate_syncvnode(mp);
 		} else {
 			if (mp->mnt_syncer != NULL)
 				vrele(mp->mnt_syncer);
@@ -1078,10 +1078,8 @@ vfs_domount(
 		mountcheckdirs(vp, newdp);
 		vrele(newdp);
 		if ((mp->mnt_flag & MNT_RDONLY) == 0)
-			error = vfs_allocate_syncvnode(mp);
+			vfs_allocate_syncvnode(mp);
 		vfs_unbusy(mp);
-		if (error)
-			vrele(vp);
 	} else {
 		vfs_unbusy(mp);
 		vfs_mount_destroy(mp);
@@ -1311,7 +1309,7 @@ dounmount(mp, flags, td)
 		mp->mnt_kern_flag &= ~MNTK_NOINSMNTQ;
 		if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL) {
 			MNT_IUNLOCK(mp);
-			(void) vfs_allocate_syncvnode(mp);
+			vfs_allocate_syncvnode(mp);
 			MNT_ILOCK(mp);
 		}
 		mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Sat Aug 28 08:39:37 2010	(r211929)
+++ head/sys/kern/vfs_subr.c	Sat Aug 28 08:57:15 2010	(r211930)
@@ -3365,7 +3365,7 @@ static struct vop_vector sync_vnodeops =
 /*
  * Create a new filesystem syncer vnode for the specified mount point.
  */
-int
+void
 vfs_allocate_syncvnode(struct mount *mp)
 {
 	struct vnode *vp;
@@ -3374,16 +3374,15 @@ vfs_allocate_syncvnode(struct mount *mp)
 	int error;
 
 	/* Allocate a new vnode */
-	if ((error = getnewvnode("syncer", mp, &sync_vnodeops, &vp)) != 0) {
-		mp->mnt_syncer = NULL;
-		return (error);
-	}
+	error = getnewvnode("syncer", mp, &sync_vnodeops, &vp);
+	if (error != 0)
+		panic("vfs_allocate_syncvnode: getnewvnode() failed");
 	vp->v_type = VNON;
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	vp->v_vflag |= VV_FORCEINSMQ;
 	error = insmntque(vp, mp);
 	if (error != 0)
-		panic("vfs_allocate_syncvnode: insmntque failed");
+		panic("vfs_allocate_syncvnode: insmntque() failed");
 	vp->v_vflag &= ~VV_FORCEINSMQ;
 	VOP_UNLOCK(vp, 0);
 	/*
@@ -3411,7 +3410,6 @@ vfs_allocate_syncvnode(struct mount *mp)
 	mtx_unlock(&sync_mtx);
 	BO_UNLOCK(bo);
 	mp->mnt_syncer = vp;
-	return (0);
 }
 
 /*

Modified: head/sys/sys/mount.h
==============================================================================
--- head/sys/sys/mount.h	Sat Aug 28 08:39:37 2010	(r211929)
+++ head/sys/sys/mount.h	Sat Aug 28 08:57:15 2010	(r211930)
@@ -730,7 +730,7 @@ void	vfs_msync(struct mount *, int);
 int	vfs_busy(struct mount *, int);
 int	vfs_export			 /* process mount export info */
 	    (struct mount *, struct export_args *);
-int	vfs_allocate_syncvnode(struct mount *);
+void	vfs_allocate_syncvnode(struct mount *);
 int	vfs_donmount(struct thread *td, int fsflags, struct uio *fsoptions);
 void	vfs_getnewfsid(struct mount *);
 struct cdev *vfs_getrootfsid(struct mount *);

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