When closing the last reference to an unlinked file, it is freed

by the inactive routine. Because the freeing causes the filesystem
to be modified, the close must be held up during periods when the
filesystem is suspended.

For snapshots to be consistent across crashes, they must write
blocks that they copy and claim those written blocks in their
on-disk block pointers before the old blocks that they referenced
can be allowed to be written.

Close a loophole that allowed unwritten blocks to be skipped when
doing ffs_sync with a request to wait for all I/O activity to be
completed.

1 files changed, 15 insertions, 6 deletions

diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index 7d48fdb..02c3eaf 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -952,7 +952,7 @@ ffs_sync(mp, waitfor, cred, p)
 	struct ucred *cred;
 	struct proc *p;
 {
-	struct vnode *nvp, *vp;
+	struct vnode *nvp, *vp, *devvp;
 	struct inode *ip;
 	struct ufsmount *ump = VFSTOUFS(mp);
 	struct fs *fs;
@@ -1026,12 +1026,21 @@ loop:
 #ifdef QUOTA
 	qsync(mp);
 #endif
-	if (waitfor != MNT_LAZY) {
-		vn_lock(ump->um_devvp, LK_EXCLUSIVE | LK_RETRY, p);
-		if ((error = VOP_FSYNC(ump->um_devvp, cred, waitfor, p)) != 0)
+	devvp = ump->um_devvp;
+	mtx_lock(&devvp->v_interlock);
+	if (waitfor != MNT_LAZY &&
+	    (devvp->v_numoutput > 0 || TAILQ_FIRST(&devvp->v_dirtyblkhd))) {
+		mtx_unlock(&devvp->v_interlock);
+		vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY, p);
+		if ((error = VOP_FSYNC(devvp, cred, waitfor, p)) != 0)
 			allerror = error;
-		VOP_UNLOCK(ump->um_devvp, 0, p);
-	}
+		VOP_UNLOCK(devvp, 0, p);
+		if (waitfor == MNT_WAIT) {
+			mtx_lock(&mntvnode_mtx);
+			goto loop;
+		}
+	} else
+		mtx_unlock(&devvp->v_interlock);
 	/*
 	 * Write back modified superblock.
 	 */