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Kernel: Simplify VMObject locking & page fault handlers

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This patch greatly simplifies VMObject locking by doing two things:

1. Giving VMObject an IntrusiveList of all its mapping Region objects.
2. Removing VMObject::m_paging_lock in favor of VMObject::m_lock

Before (1), VMObject::for_each_region() was forced to acquire the
global MM lock (since it worked by walking MemoryManager's list of
all regions and checking for regions that pointed to itself.)

With each VMObject having its own list of Regions, VMObject's own
m_lock is all we need.

Before (2), page fault handlers used a separate mutex for preventing
overlapping work. This design required multiple temporary unlocks
and was generally extremely hard to reason about.

Instead, page fault handlers now use VMObject's own m_lock as well.
This commit is contained in:
Andreas Kling 2021-07-23 02:40:16 +02:00
parent 64babcaa83
commit 082ed6f417
10 changed files with 116 additions and 155 deletions
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27
Kernel/VM/Region.h
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@ -15,10 +15,10 @@
#include <Kernel/Heap/SlabAllocator.h>
#include <Kernel/KString.h>
#include <Kernel/Sections.h>
#include <Kernel/UnixTypes.h>
#include <Kernel/VM/PageFaultResponse.h>
#include <Kernel/VM/PurgeablePageRanges.h>
#include <Kernel/VM/RangeAllocator.h>
#include <Kernel/VM/VMObject.h>
namespace Kernel {
@ -88,7 +88,7 @@ public:
bool is_user() const { return !is_kernel(); }
bool is_kernel() const { return vaddr().get() < 0x00800000 || vaddr().get() >= kernel_base; }
PageFaultResponse handle_fault(PageFault const&, ScopedSpinLock<RecursiveSpinLock>&);
PageFaultResponse handle_fault(PageFault const&);
OwnPtr<Region> clone(Process&);
@ -165,17 +165,8 @@ public:
return size() / PAGE_SIZE;
}
PhysicalPage const* physical_page(size_t index) const
{
VERIFY(index < page_count());
return vmobject().physical_pages()[first_page_index() + index];
}
RefPtr<PhysicalPage>& physical_page_slot(size_t index)
{
VERIFY(index < page_count());
return vmobject().physical_pages()[first_page_index() + index];
}
PhysicalPage const* physical_page(size_t index) const;
RefPtr<PhysicalPage>& physical_page_slot(size_t index);
size_t offset_in_vmobject() const
{
@ -242,8 +233,8 @@ private:
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, ScopedSpinLock<RecursiveSpinLock>&);
PageFaultResponse handle_zero_fault(size_t page_index, ScopedSpinLock<RecursiveSpinLock>&);
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);
@ -262,10 +253,12 @@ private:
bool m_mmap : 1 { false };
bool m_syscall_region : 1 { false };
WeakPtr<Process> m_owner;
IntrusiveListNode<Region> m_list_node;
IntrusiveListNode<Region> m_memory_manager_list_node;
IntrusiveListNode<Region> m_vmobject_list_node;
public:
using List = IntrusiveList<Region, RawPtr<Region>, &Region::m_list_node>;
using ListInMemoryManager = IntrusiveList<Region, RawPtr<Region>, &Region::m_memory_manager_list_node>;
using ListInVMObject = IntrusiveList<Region, RawPtr<Region>, &Region::m_vmobject_list_node>;
};
AK_ENUM_BITWISE_OPERATORS(Region::Access)