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);
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