Kernel: Make purgeable memory a VMObject level concept (again)

This patch changes the semantics of purgeable memory.

- AnonymousVMObject now has a "purgeable" flag. It can only be set when
  constructing the object. (Previously, all anonymous memory was
  effectively purgeable.)

- AnonymousVMObject now has a "volatile" flag. It covers the entire
  range of physical pages. (Previously, we tracked ranges of volatile
  pages, effectively making it a page-level concept.)

- Non-volatile objects maintain a physical page reservation via the
  committed pages mechanism, to ensure full coverage for page faults.

- When an object is made volatile, it relinquishes any unused committed
  pages immediately. If later made non-volatile again, we then attempt
  to make a new committed pages reservation. If this fails, we return
  ENOMEM to userspace.

mmap() now creates purgeable objects if passed the MAP_PURGEABLE option
together with MAP_ANONYMOUS. anon_create() memory is always purgeable.

1 files changed, 3 insertions, 14 deletions

diff --git a/Kernel/VM/Region.h b/Kernel/VM/Region.h
index 34e76802bc..af680e6185 100644
--- a/Kernel/VM/Region.h
+++ b/Kernel/VM/Region.h
@@ -17,7 +17,6 @@
 #include <Kernel/Sections.h>
 #include <Kernel/UnixTypes.h>
 #include <Kernel/VM/PageFaultResponse.h>
-#include <Kernel/VM/PurgeablePageRanges.h>
 #include <Kernel/VM/RangeAllocator.h>
 
 namespace Kernel {
@@ -28,8 +27,7 @@ enum class ShouldFlushTLB {
 };
 
 class Region final
-    : public Weakable<Region>
-    , public PurgeablePageRanges {
+    : public Weakable<Region> {
     friend class MemoryManager;
 
     MAKE_SLAB_ALLOCATED(Region)
@@ -201,15 +199,11 @@ public:
 
     void remap();
 
-    bool remap_vmobject_page_range(size_t page_index, size_t page_count);
-
-    bool is_volatile(VirtualAddress vaddr, size_t size) const;
     enum class SetVolatileError {
         Success = 0,
         NotPurgeable,
         OutOfMemory
     };
-    SetVolatileError set_volatile(VirtualAddress vaddr, size_t size, bool is_volatile, bool& was_purged);
 
     RefPtr<Process> get_owner();
 
@@ -219,7 +213,8 @@ public:
 private:
     Region(Range const&, NonnullRefPtr<VMObject>, size_t offset_in_vmobject, OwnPtr<KString>, Region::Access access, Cacheable, bool shared);
 
-    bool do_remap_vmobject_page_range(size_t page_index, size_t page_count);
+    bool remap_vmobject_page(size_t page_index, bool with_flush = true);
+    bool do_remap_vmobject_page(size_t page_index, bool with_flush = true);
 
     void set_access_bit(Access access, bool b)
     {
@@ -229,18 +224,12 @@ private:
             m_access &= ~access;
     }
 
-    bool do_remap_vmobject_page(size_t index, bool with_flush = true);
-    bool remap_vmobject_page(size_t index, bool with_flush = true);
-
     PageFaultResponse handle_cow_fault(size_t page_index);
     PageFaultResponse handle_inode_fault(size_t page_index);
     PageFaultResponse handle_zero_fault(size_t page_index);
 
     bool map_individual_page_impl(size_t page_index);
 
-    void register_purgeable_page_ranges();
-    void unregister_purgeable_page_ranges();
-
     RefPtr<PageDirectory> m_page_directory;
     Range m_range;
     size_t m_offset_in_vmobject { 0 };