svn commit: r299946 - in head/sys/cddl/contrib/opensolaris/uts/common/fs: . zfs

[Andriy Gapon]

Author: avg
Date: Mon May 16 15:13:16 2016
New Revision: 299946
URL: https://svnweb.freebsd.org/changeset/base/299946

Log:
  gfs_lookup_dot() does not have to acquire any locks
  
  In fact, that was dangerous.  For example, zfsctl_snapshot_reclaim()
  calls gfs_dir_lookup() on ".." path and that ends up calling
  gfs_lookup_dot() which violated locking order by acquiring the parent's
  directory vnode lock after the child's vnode lock.
  
  Also, the previous behavior was inconsistent as gfs_dir_lookup()
  returned a locked vnode for . and .. lookups, but not for any other.
  
  Now gfs_lookup_dot() just references a resulting vnode and the locking
  is done in its consumers, where necessary.
  Note that we do not enable shared locking support for any gfs / zfsctl
  vnodes.
  
  This commit partially reverts r273641.
  
  MFC after:	5 weeks

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/gfs.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/gfs.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/gfs.c	Mon May 16 15:03:52 2016	(r299945)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/gfs.c	Mon May 16 15:13:16 2016	(r299946)
@@ -442,19 +442,9 @@ gfs_lookup_dot(vnode_t **vpp, vnode_t *d
 		*vpp = dvp;
 		return (0);
 	} else if (strcmp(nm, "..") == 0) {
-		if (pvp == NULL) {
-			ASSERT(dvp->v_flag & VROOT);
-			VN_HOLD(dvp);
-			*vpp = dvp;
-			ASSERT_VOP_ELOCKED(dvp, "gfs_lookup_dot: non-locked dvp");
-		} else {
-			ltype = VOP_ISLOCKED(dvp);
-			VOP_UNLOCK(dvp, 0);
-			VN_HOLD(pvp);
-			*vpp = pvp;
-			vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY);
-			vn_lock(dvp, ltype | LK_RETRY);
-		}
+		ASSERT(pvp != NULL);
+		VN_HOLD(pvp);
+		*vpp = pvp;
 		return (0);
 	}
 

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c	Mon May 16 15:03:52 2016	(r299945)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c	Mon May 16 15:13:16 2016	(r299946)
@@ -987,6 +987,11 @@ zfsctl_snapdir_lookup(ap)
 
 	ZFS_ENTER(zfsvfs);
 	if (gfs_lookup_dot(vpp, dvp, zfsvfs->z_ctldir, nm) == 0) {
+		if (nm[0] == '.' && nm[1] == '.' && nm[2] =='\0') {
+			VOP_UNLOCK(dvp, 0);
+			VERIFY0(vn_lock(*vpp, LK_EXCLUSIVE));
+			VERIFY0(vn_lock(dvp, LK_EXCLUSIVE));
+		}
 		ZFS_EXIT(zfsvfs);
 		return (0);
 	}
@@ -1151,6 +1156,11 @@ zfsctl_shares_lookup(ap)
 	strlcpy(nm, cnp->cn_nameptr, cnp->cn_namelen + 1);
 
 	if (gfs_lookup_dot(vpp, dvp, zfsvfs->z_ctldir, nm) == 0) {
+		if (nm[0] == '.' && nm[1] == '.' && nm[2] =='\0') {
+			VOP_UNLOCK(dvp, 0);
+			VERIFY0(vn_lock(*vpp, LK_EXCLUSIVE));
+			VERIFY0(vn_lock(dvp, LK_EXCLUSIVE));
+		}
 		ZFS_EXIT(zfsvfs);
 		return (0);
 	}
@@ -1488,7 +1498,6 @@ zfsctl_snapshot_reclaim(ap)
 
 	VERIFY(gfs_dir_lookup(vp, "..", &dvp, cr, 0, NULL, NULL) == 0);
 	sdp = dvp->v_data;
-	VOP_UNLOCK(dvp, 0);
 	/* this may already have been unmounted */
 	if (sdp == NULL) {
 		VN_RELE(dvp);