LU-5422 obdclass: Fix null pointer derefs in lu_cache_shrink()

When lu_cache_shrink() is called on a machine with no Lustre targets
mounted, the following null pointer dereference may happen:

  BUG: unable to handle kernel NULL pointer dereference at (null)
  IP: [<ffffffffa0aed076>] lu_cache_shrink+0x156/0x310 [obdclass]

This is a regression introduced recently by 8701e7e.  lu_sites must be
initialized before the lu_sites shrinker is registered.  And, it
cannot be re-initialized every time when an lu_site is initialized.

Change-Id: Ieebd2ff1bcde4096037658a22956355283122182
Signed-off-by: Li Wei <wei.g.li@intel.com>
Reviewed-on: http://review.whamcloud.com/11244
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/obdclass/lu_object.c b/lustre/obdclass/lu_object.c
index cc43d7c..d880ba4 100644 (file)
--- a/lustre/obdclass/lu_object.c
+++ b/lustre/obdclass/lu_object.c
@@ -1098,8 +1098,6 @@ int lu_site_init(struct lu_site *s, struct lu_device *top)
        int i;
        ENTRY;
 
-       INIT_LIST_HEAD(&lu_sites);
-
        memset(s, 0, sizeof *s);
        mutex_init(&s->ls_purge_mutex);
        bits = lu_htable_order(top);
@@ -2112,6 +2110,7 @@ int lu_global_init(void)
 
        INIT_LIST_HEAD(&lu_device_types);
        INIT_LIST_HEAD(&lu_context_remembered);
+       INIT_LIST_HEAD(&lu_sites);
 
         result = lu_ref_global_init();
         if (result != 0)