Before invoking vnode operations on cache vnodes, acquire the vnode

locks of those vnodes.  Probably, Coda should do the same lock sharing/
pass-through that is done for nullfs, but in the mean time this ensures
that locks are adequately held to prevent corruption of data structures
in the cache file system.

Assuming most operations came from the top layer of Coda and weren't
performed directly on the cache vnodes, in practice this corruption was
relatively unlikely as the Coda vnode locks were ensuring exclusive
access for most consumers.

This causes WITNESS to squeal like a pig immediately when Coda is used,
rather than waiting until file close; I noticed these problems because
of the lack of said squealing.

MFC after:	1 month

1 files changed, 9 insertions, 1 deletions

diff --git a/sys/fs/coda/coda_vnops.c b/sys/fs/coda/coda_vnops.c
index 6074938..8e1e49d 100644
--- a/sys/fs/coda/coda_vnops.c
+++ b/sys/fs/coda/coda_vnops.c
@@ -234,13 +234,16 @@ coda_open(struct vop_open_args *ap)
     }
 
     /* Open the cache file. */
+    vn_lock(vp, LK_EXCLUSIVE);
     error = VOP_OPEN(vp, flag, cred, td, NULL); 
     if (error) {
+	VOP_UNLOCK(vp, 0);
     	printf("coda_open: VOP_OPEN on container failed %d\n", error);
 	return (error);
     } else {
 	(*vpp)->v_object = vp->v_object;
     }
+    VOP_UNLOCK(vp, 0);
 /* grab (above) does this when it calls newvnode unless it's in the cache*/
 
     return(error);
@@ -270,8 +273,9 @@ coda_close(struct vop_close_args *ap)
     }
 
     if (cp->c_ovp) {
+	vn_lock(cp->c_ovp, LK_EXCLUSIVE);
 	VOP_CLOSE(cp->c_ovp, flag, cred, td); /* Do errors matter here? */
-	vrele(cp->c_ovp);
+	vput(cp->c_ovp);
     }
 #ifdef CODA_VERBOSE
     else printf("coda_close: NO container vp %p/cp %p\n", vp, cp);
@@ -354,6 +358,7 @@ coda_rdwr(struct vnode *vp, struct uio *uiop, enum uio_rw rw, int ioflag,
     /* Have UFS handle the call. */
     CODADEBUG(CODA_RDWR, myprintf(("indirect rdwr: fid = %s, refcnt = %d\n",
 			     coda_f2s(&cp->c_fid), CTOV(cp)->v_usecount)); )
+    vn_lock(cfvp, LK_EXCLUSIVE);
     if (rw == UIO_READ) {
 	error = VOP_READ(cfvp, uiop, ioflag, cred);
     } else {
@@ -367,6 +372,7 @@ coda_rdwr(struct vnode *vp, struct uio *uiop, enum uio_rw rw, int ioflag,
 	    }
 	}
     }
+    VOP_UNLOCK(cfvp, 0);
 
     if (error)
 	MARK_INT_FAIL(CODA_RDWR_STATS);
@@ -1457,8 +1463,10 @@ coda_readdir(struct vop_readdir_args *ap)
 	
 	/* Have UFS handle the call. */
 	CODADEBUG(CODA_READDIR, myprintf(("indirect readdir: fid = %s, refcnt = %d\n", coda_f2s(&cp->c_fid), vp->v_usecount)); )
+	vn_lock(cp->c_ovp, LK_EXCLUSIVE);
 	error = VOP_READDIR(cp->c_ovp, uiop, cred, eofflag, ncookies,
 			       cookies);
+	VOP_UNLOCK(cp->c_ovp, 0);
 	
 	if (error)
 	    MARK_INT_FAIL(CODA_READDIR_STATS);