Author: avg
Date: Sat Apr 3 08:53:53 2010
New Revision: 206130
URL: http://svn.freebsd.org/changeset/base/206130
Log:
g_vfs_open: allow only one mount per device vnode
In other words, deny multiple read-only mounts of the same device.
Shared read-only mounts should theoretically be possible, but,
unfortunately, can not be implemented correctly using current
buffer cache code/interface and results in an eventual system crash.
Also, using nullfs seems to be a more efficient way to achieve the same
goal.
This gets us back to where we were before GEOM and where other BSDs are.
Submitted by: pjd (idea for checking for shared mounting)
Discussed with: phk, pjd
Silence from: fs@, geom@
MFC after: 2 weeks
Modified:
head/sys/geom/geom_vfs.c
Modified: head/sys/geom/geom_vfs.c
==============================================================================
--- head/sys/geom/geom_vfs.c Sat Apr 3 08:39:00 2010 (r206129)
+++ head/sys/geom/geom_vfs.c Sat Apr 3 08:53:53 2010 (r206130)
@@ -161,6 +161,10 @@ g_vfs_open(struct vnode *vp, struct g_co
g_topology_assert();
*cpp = NULL;
+ bo = &vp->v_bufobj;
+ if (bo->bo_private != vp)
+ return (EBUSY);
+
pp = g_dev_getprovider(vp->v_rdev);
if (pp == NULL)
return (ENOENT);
@@ -176,7 +180,7 @@ g_vfs_open(struct vnode *vp, struct g_co
vnode_create_vobject(vp, pp->mediasize, curthread);
VFS_UNLOCK_GIANT(vfslocked);
*cpp = cp;
- bo = &vp->v_bufobj;
+ cp->private = vp;
bo->bo_ops = g_vfs_bufops;
bo->bo_private = cp;
bo->bo_bsize = pp->sectorsize;
@@ -196,5 +200,6 @@ g_vfs_close(struct g_consumer *cp)
gp = cp->geom;
bo = gp->softc;
bufobj_invalbuf(bo, V_SAVE, 0, 0);
+ bo->bo_private = cp->private;
g_wither_geom_close(gp, ENXIO);
}
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