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zfsctl: fix several problems with reference counts

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* Remove excessive references on a snapshot mountpoint vnode.
  zfsctl_snapdir_lookup() called VN_HOLD() on a vnode returned from
  zfsctl_snapshot_mknode() and the latter also had a call to VN_HOLD()
  on the same vnode.
  On top of that gfs_dir_create() already returns the vnode with the
  use count of 1 (set in getnewvnode).
  So there was 3 references on the vnode.

* mount_snapshot() should keep a reference to a covered vnode.
  That reference is owned by the mountpoint (mounted snapshot filesystem).

* Remove cryptic manipulations of a covered vnode in zfs_umount().
  FreeBSD dounmount() already does the right thing and releases the covered
  vnode.

PR:		207464
Reported by:	dustinwenz@ebureau.com
Tested by:	Howard Powell <hpowell@lighthouseinstruments.com>
MFC after:	3 weeks
This commit is contained in:
Andriy Gapon 2016-05-16 06:24:04 +00:00
parent 7d4ce67a76
commit 3055925d42
3 changed files with 1 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
View File

@ -229,7 +229,7 @@ mount_snapshot(kthread_t *td, vnode_t **vpp, const char *fstype, char *fspath,
vfs_event_signal(NULL, VQ_MOUNT, 0);
if (VFS_ROOT(mp, LK_EXCLUSIVE, &mvp))
panic("mount: lost mount");
vput(vp);
VOP_UNLOCK(vp, 0);
vfs_unbusy(mp);
*vpp = mvp;
return (0);

2
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
View File

@ -1076,7 +1076,6 @@ zfsctl_snapdir_lookup(ap)
sep->se_name = kmem_alloc(strlen(nm) + 1, KM_SLEEP);
(void) strcpy(sep->se_name, nm);
*vpp = sep->se_root = zfsctl_snapshot_mknode(dvp, dmu_objset_id(snap));
VN_HOLD(*vpp);
avl_insert(&sdp->sd_snaps, sep, where);
dmu_objset_rele(snap, FTAG);
@ -1454,7 +1453,6 @@ zfsctl_snapshot_mknode(vnode_t *pvp, uint64_t objset)
vp = gfs_dir_create(sizeof (zfsctl_node_t), pvp, pvp->v_vfsp,
&zfsctl_ops_snapshot, NULL, NULL, MAXNAMELEN, NULL, NULL);
VN_HOLD(vp);
zcp = vp->v_data;
zcp->zc_id = objset;
VOP_UNLOCK(vp, 0);

6
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
View File

@ -2005,12 +2005,6 @@ zfs_umount(vfs_t *vfsp, int fflag)
*/
if (zfsvfs->z_ctldir != NULL)
zfsctl_destroy(zfsvfs);
if (zfsvfs->z_issnap) {
vnode_t *svp = vfsp->mnt_vnodecovered;
if (svp->v_count >= 2)
VN_RELE(svp);
}
zfs_freevfs(vfsp);
return (0);