kernel/slab: Change checks in FreeRawOrReturnCache to panic instead.

The function is largely useless if we cannot lock kernel space,
and the consumers may not expect it to silently "fail." Hence,
we now put the invocation of deferred_free in free_etc directly.

src/system/kernel/slab/MemoryManager.cpp

@@ -697,6 +697,11 @@ MemoryManager::FreeRawOrReturnCache(void* pages, uint32 flags)
 
 	T(FreeRawOrReturnCache(pages, flags));
 
+	if ((flags & CACHE_DONT_LOCK_KERNEL_SPACE) != 0) {
+		panic("cannot proceed without locking kernel space!");
+		return NULL;
+	}
+
 	// get the area
 	addr_t areaBase = _AreaBaseAddressForAddress((addr_t)pages);
 
@@ -705,14 +710,7 @@ MemoryManager::FreeRawOrReturnCache(void* pages, uint32 flags)
 	readLocker.Unlock();
 
 	if (area == NULL) {
-		// Probably a large allocation.
-		if ((flags & CACHE_DONT_LOCK_KERNEL_SPACE) != 0) {
-			// We cannot delete areas without locking the kernel address space,
-			// so defer the free until we can do that.
-			deferred_free(pages);
-			return NULL;
-		}
-
+		// Probably a large allocation. Look up the VM area.
 		VMAddressSpace* addressSpace = VMAddressSpace::Kernel();
 		addressSpace->ReadLock();
 		VMArea* area = addressSpace->LookupArea((addr_t)pages);
@@ -746,12 +744,6 @@ MemoryManager::FreeRawOrReturnCache(void* pages, uint32 flags)
 	size_t size = reference - (addr_t)pages + 1;
 	ASSERT((size % SLAB_CHUNK_SIZE_SMALL) == 0);
 
-	// Verify we can actually lock the kernel space before going further.
-	if ((flags & CACHE_DONT_LOCK_KERNEL_SPACE) != 0) {
-		deferred_free(pages);
-		return NULL;
-	}
-
 	// unmap the chunks
 	_UnmapChunk(area->vmArea, (addr_t)pages, size, flags);
 

src/system/kernel/slab/allocator.cpp

@@ -242,6 +242,11 @@ aligned_alloc(size_t alignment, size_t size)
 void
 free_etc(void *address, uint32 flags)
 {
+	if ((flags & CACHE_DONT_LOCK_KERNEL_SPACE) != 0) {
+		deferred_free(address);
+		return;
+	}
+
 	block_free(address, flags & CACHE_ALLOC_FLAGS);
 }