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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 30 Jun 2009 10:07:33 +0000 (UTC)
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Subject: svn commit: r195187 - head/sys/ufs/ffs
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Author: kib
Date: Tue Jun 30 10:07:33 2009
New Revision: 195187
URL: http://svn.freebsd.org/changeset/base/195187

Log:
  For SU mounts, softdep_fsync() might drop vnode lock, allowing other
  threads to put dirty buffers on the vnode bufobj list. For regular files
  and synchronous fsync requests, check for the condition and restart the
  fsync vop if a new dirty buffer arrived.
  
  Tested by:	pho
  Approved by:	re (kensmith)
  MFC after:	1 month

Modified:
  head/sys/ufs/ffs/ffs_vnops.c

Modified: head/sys/ufs/ffs/ffs_vnops.c
==============================================================================
--- head/sys/ufs/ffs/ffs_vnops.c	Tue Jun 30 10:07:00 2009	(r195186)
+++ head/sys/ufs/ffs/ffs_vnops.c	Tue Jun 30 10:07:33 2009	(r195187)
@@ -180,15 +180,36 @@ struct vop_vector ffs_fifoops2 = {
 static int
 ffs_fsync(struct vop_fsync_args *ap)
 {
+	struct vnode *vp;
+	struct bufobj *bo;
 	int error;
 
-	error = ffs_syncvnode(ap->a_vp, ap->a_waitfor);
+	vp = ap->a_vp;
+	bo = &vp->v_bufobj;
+retry:
+	error = ffs_syncvnode(vp, ap->a_waitfor);
 	if (error)
 		return (error);
 	if (ap->a_waitfor == MNT_WAIT &&
-	    (ap->a_vp->v_mount->mnt_flag & MNT_SOFTDEP))
-                error = softdep_fsync(ap->a_vp);
-	return (error);
+	    (vp->v_mount->mnt_flag & MNT_SOFTDEP)) {
+		error = softdep_fsync(vp);
+		if (error)
+			return (error);
+
+		/*
+		 * The softdep_fsync() function may drop vp lock,
+		 * allowing for dirty buffers to reappear on the
+		 * bo_dirty list. Recheck and resync as needed.
+		 */
+		BO_LOCK(bo);
+		if (vp->v_type == VREG && (bo->bo_numoutput > 0 ||
+		    bo->bo_dirty.bv_cnt > 0)) {
+			BO_UNLOCK(bo);
+			goto retry;
+		}
+		BO_UNLOCK(bo);
+	}
+	return (0);
 }
 
 int