shadow collapse fix

3 files changed, 25 insertions, 38 deletions

diff --git a/kernel/vm/pagefault.c b/kernel/vm/pagefault.c
index 4be12cd..47b3312 100644
--- a/kernel/vm/pagefault.c
+++ b/kernel/vm/pagefault.c
@@ -53,11 +53,7 @@ void handle_pagefault(uintptr_t vaddr, uintptr_t cause)
     // NOT_YET_IMPLEMENTED("VM: handle_pagefault");
 
     // Check that the vaddr is valid
-    if (vaddr < USER_MEM_LOW) 
-    {
-        do_exit(EFAULT);
-    }
-    if (vaddr > USER_MEM_HIGH) 
+    if (vaddr < USER_MEM_LOW ||vaddr > USER_MEM_HIGH) 
     {
         do_exit(EFAULT);
     }
diff --git a/kernel/vm/shadow.c b/kernel/vm/shadow.c
index e0a8674..ca20ab0 100644
--- a/kernel/vm/shadow.c
+++ b/kernel/vm/shadow.c
@@ -119,58 +119,49 @@ void shadow_collapse(mobj_t *o)
     // NOT_YET_IMPLEMENTED("VM: shadow_collapse");
 
     mobj_shadow_t *so = MOBJ_TO_SO(o);
-    mobj_t *shadowed = so->shadowed;
-
-    if (shadowed->mo_type != MOBJ_SHADOW)
-    {
-        return;
-    }
-
-    dbg(DBG_PRINT, "shadow_collapse: refcount bottom: %d\n", so->bottom_mobj->mo_refcount);
-
-    while (shadowed && shadowed->mo_type == MOBJ_SHADOW)
+    mobj_t *next = so->shadowed;
+    while(next && next->mo_type==MOBJ_SHADOW)
     {
-        // mobj_shadow_t *so_shadowed = MOBJ_TO_SO(shadowed);
-        mobj_t *shadowed_shadowed = MOBJ_TO_SO(shadowed)->shadowed;
 
-        // if the refcount is not 1, then we can't collapse
-        if (shadowed_shadowed->mo_refcount != 1)
+        // check if the shadowed object is collapsable
+        if (next->mo_refcount != 1) 
         {
-            // continue down the shadow chain
-            shadowed = shadowed_shadowed;
+            // continue on the shadow chain
+            so = MOBJ_TO_SO(next);
+            next = MOBJ_TO_SO(next)->shadowed;
             continue;
         }
 
-        mobj_lock(shadowed_shadowed);
-        list_iterate(&shadowed_shadowed->mo_pframes, pf, pframe_t, pf_link)
+        // migrate the pframes from o's shadowed object to o
+        // mobj_lock(next); // lock before iterover
+        list_iterate(&next->mo_pframes, pf, pframe_t, pf_link)
         {
             pframe_t *pf_shadow = NULL;
-            mobj_find_pframe(shadowed_shadowed, pf->pf_pagenum, &pf_shadow);
+            mobj_lock(&so->mobj);
+            mobj_find_pframe(&so->mobj, pf->pf_pagenum, &pf_shadow);
+            mobj_unlock(&so->mobj);
             if (!pf_shadow)
             {
                 list_remove(&pf->pf_link);
-                // append to the list of pframes
-                list_insert_tail(&shadowed_shadowed->mo_pframes, &pf->pf_link);
+                // by migrate, just add to the list of pframes
+                list_insert_tail(&so->mobj.mo_pframes, &pf->pf_link);
             }
             else
             {
+                // if it exists, just release it
                 pframe_release(&pf_shadow);
             }
         }
 
-        // get the pointer to the shadowed object
-        mobj_shadow_t *so_shadowed_shadowed = MOBJ_TO_SO(shadowed_shadowed);
-        so->shadowed = shadowed_shadowed;
+        // update the pointer to the shadowed object
+        so->shadowed = MOBJ_TO_SO(next)->shadowed;
 
-        mobj_lock(so->shadowed);
+        // update the refcounts
         mobj_ref(so->shadowed);
-        mobj_unlock(so->shadowed);
-
-        // put the shadowed object
-        mobj_put(&shadowed);
+        mobj_put(&next);
 
-        // continue down the shadow chain
-        shadowed = shadowed_shadowed;
+        // update next
+        next = so->shadowed;
     }
 }
 
diff --git a/kernel/vm/vmmap.c b/kernel/vm/vmmap.c
index ad95d33..e301ac0 100644
--- a/kernel/vm/vmmap.c
+++ b/kernel/vm/vmmap.c
@@ -270,9 +270,9 @@ void vmmap_collapse(vmmap_t *map)
     {
         if (vma->vma_obj->mo_type == MOBJ_SHADOW)
         {
-            mobj_lock(vma->vma_obj);
+            // mobj_lock(vma->vma_obj);
             shadow_collapse(vma->vma_obj);
-            mobj_unlock(vma->vma_obj);
+            // mobj_unlock(vma->vma_obj);
         }
     }
 }