Revert "Kernel: Only update page tables for faulting region"

This reverts commit 1c5ffaae41be4e67f81b46c3bfdce7f54a1dc8e0.

This broke shared memory as used by OutOfProcessWebView. Let's do
a revert until we can figure out what went wrong.

Kernel/Memory/Region.cpp

@@ -220,18 +220,33 @@ bool Region::map_individual_page_impl(size_t page_index)
     return true;
 }
 
-bool Region::remap_individual_page(size_t page_index, ShouldFlushTLB should_flush_tlb)
+bool Region::do_remap_vmobject_page(size_t page_index, bool with_flush)
 {
-    VERIFY(m_page_directory);
+    if (!m_page_directory)
+        return true; // not an error, region may have not yet mapped it
+    if (!translate_vmobject_page(page_index))
+        return true; // not an error, region doesn't map this page
     SpinlockLocker page_lock(m_page_directory->get_lock());
     SpinlockLocker lock(s_mm_lock);
     VERIFY(physical_page(page_index));
     bool success = map_individual_page_impl(page_index);
-    if (should_flush_tlb == ShouldFlushTLB::Yes)
+    if (with_flush)
         MemoryManager::flush_tlb(m_page_directory, vaddr_from_page_index(page_index));
     return success;
 }
 
+bool Region::remap_vmobject_page(size_t page_index, bool with_flush)
+{
+    auto& vmobject = this->vmobject();
+    bool success = true;
+    SpinlockLocker lock(vmobject.m_lock);
+    vmobject.for_each_region([&](auto& region) {
+        if (!region.do_remap_vmobject_page(page_index, with_flush))
+            success = false;
+    });
+    return success;
+}
+
 void Region::unmap(ShouldDeallocateVirtualRange should_deallocate_range, ShouldFlushTLB should_flush_tlb)
 {
     if (!m_page_directory)
@@ -343,9 +358,10 @@ PageFaultResponse Region::handle_fault(PageFault const& fault)
 
         auto& page_slot = physical_page_slot(page_index_in_region);
         if (page_slot->is_lazy_committed_page()) {
+            auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region);
             VERIFY(m_vmobject->is_anonymous());
             page_slot = static_cast<AnonymousVMObject&>(*m_vmobject).allocate_committed_page({});
-            if (!remap_individual_page(page_index_in_region))
+            if (!remap_vmobject_page(page_index_in_vmobject))
                 return PageFaultResponse::OutOfMemory;
             return PageFaultResponse::Continue;
         }
@@ -372,12 +388,13 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
     VERIFY(vmobject().is_anonymous());
 
     auto& page_slot = physical_page_slot(page_index_in_region);
+    auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region);
 
     SpinlockLocker locker(vmobject().m_lock);
 
     if (!page_slot.is_null() && !page_slot->is_shared_zero_page() && !page_slot->is_lazy_committed_page()) {
         dbgln_if(PAGE_FAULT_DEBUG, "MM: zero_page() but page already present. Fine with me!");
-        if (!remap_individual_page(page_index_in_region))
+        if (!remap_vmobject_page(page_index_in_vmobject))
             return PageFaultResponse::OutOfMemory;
         return PageFaultResponse::Continue;
     }
@@ -400,7 +417,7 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
         dbgln_if(PAGE_FAULT_DEBUG, "      >> ALLOCATED {}", page_slot->paddr());
     }
 
-    if (!remap_individual_page(page_index_in_region)) {
+    if (!remap_vmobject_page(page_index_in_vmobject)) {
         dmesgln("MM: handle_zero_fault was unable to allocate a page table to map {}", page_slot);
         return PageFaultResponse::OutOfMemory;
     }
@@ -419,7 +436,7 @@ PageFaultResponse Region::handle_cow_fault(size_t page_index_in_region)
 
     auto page_index_in_vmobject = translate_to_vmobject_page(page_index_in_region);
     auto response = reinterpret_cast<AnonymousVMObject&>(vmobject()).handle_cow_fault(page_index_in_vmobject, vaddr().offset(page_index_in_region * PAGE_SIZE));
-    if (!remap_individual_page(page_index_in_region))
+    if (!remap_vmobject_page(page_index_in_vmobject))
         return PageFaultResponse::OutOfMemory;
     return response;
 }
@@ -440,7 +457,7 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
         SpinlockLocker locker(inode_vmobject.m_lock);
         if (!vmobject_physical_page_entry.is_null()) {
             dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else before reading, remapping.");
-            if (!remap_individual_page(page_index_in_region))
+            if (!remap_vmobject_page(page_index_in_vmobject))
                 return PageFaultResponse::OutOfMemory;
             return PageFaultResponse::Continue;
         }
@@ -475,7 +492,7 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
         // Someone else faulted in this page while we were reading from the inode.
         // No harm done (other than some duplicate work), remap the page here and return.
         dbgln_if(PAGE_FAULT_DEBUG, "handle_inode_fault: Page faulted in by someone else, remapping.");
-        if (!remap_individual_page(page_index_in_region))
+        if (!remap_vmobject_page(page_index_in_vmobject))
             return PageFaultResponse::OutOfMemory;
         return PageFaultResponse::Continue;
     }
@@ -494,7 +511,7 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
         MM.unquickmap_page();
     }
 
-    if (!remap_individual_page(page_index_in_region))
+    if (!remap_vmobject_page(page_index_in_vmobject))
         return PageFaultResponse::OutOfMemory;
 
     return PageFaultResponse::Continue;

Kernel/Memory/Region.h

@@ -196,7 +196,8 @@ public:
 private:
     Region(VirtualRange const&, NonnullRefPtr<VMObject>, size_t offset_in_vmobject, OwnPtr<KString>, Region::Access access, Cacheable, bool shared);
 
-    [[nodiscard]] bool remap_individual_page(size_t page_index, ShouldFlushTLB = ShouldFlushTLB::Yes);
+    [[nodiscard]] bool remap_vmobject_page(size_t page_index, bool with_flush = true);
+    [[nodiscard]] bool do_remap_vmobject_page(size_t page_index, bool with_flush = true);
 
     void set_access_bit(Access access, bool b)
     {