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.

Kernel/CMakeLists.txt

@@ -264,7 +264,6 @@ set(KERNEL_SOURCES
     VM/PhysicalZone.cpp
     VM/PrivateInodeVMObject.cpp
     VM/ProcessPagingScope.cpp
-    VM/PurgeablePageRanges.cpp
     VM/Range.cpp
     VM/RangeAllocator.cpp
     VM/Region.cpp

Kernel/FileSystem/AnonymousFile.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/FileSystem/File.h>
+#include <Kernel/VM/AnonymousVMObject.h>
 
 namespace Kernel {
 

Kernel/ProcessSpecificExposed.cpp

@@ -456,7 +456,7 @@ private:
                 region_object.add("syscall", region->is_syscall_region());
                 region_object.add("purgeable", region->vmobject().is_anonymous());
                 if (region->vmobject().is_anonymous()) {
-                    region_object.add("volatile", static_cast<const AnonymousVMObject&>(region->vmobject()).is_any_volatile());
+                    region_object.add("volatile", static_cast<AnonymousVMObject const&>(region->vmobject()).is_volatile());
                 }
                 region_object.add("cacheable", region->is_cacheable());
                 region_object.add("address", region->vaddr().get());

Kernel/Syscalls/anon_create.cpp

@@ -29,7 +29,7 @@ KResultOr<FlatPtr> Process::sys$anon_create(size_t size, int options)
     if (new_fd < 0)
         return new_fd;
 
-    auto vmobject = AnonymousVMObject::try_create_with_size(size, AllocationStrategy::Reserve);
+    auto vmobject = AnonymousVMObject::try_create_purgeable_with_size(size, AllocationStrategy::Reserve);
     if (!vmobject)
         return ENOMEM;
 

Kernel/Syscalls/mmap.cpp

@@ -12,6 +12,7 @@
 #include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
+#include <Kernel/VM/AnonymousVMObject.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/PageDirectory.h>
 #include <Kernel/VM/PrivateInodeVMObject.h>
@@ -217,7 +218,14 @@ KResultOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> u
 
     if (map_anonymous) {
         auto strategy = map_noreserve ? AllocationStrategy::None : AllocationStrategy::Reserve;
-        auto region_or_error = space().allocate_region(range.value(), {}, prot, strategy);
+        RefPtr<AnonymousVMObject> vmobject;
+        if (flags & MAP_PURGEABLE)
+            vmobject = AnonymousVMObject::try_create_purgeable_with_size(page_round_up(size), strategy);
+        else
+            vmobject = AnonymousVMObject::try_create_with_size(page_round_up(size), strategy);
+        if (!vmobject)
+            return ENOMEM;
+        auto region_or_error = space().allocate_region_with_vmobject(range.value(), vmobject.release_nonnull(), 0, {}, prot, map_shared);
         if (region_or_error.is_error())
             return region_or_error.error().error();
         region = region_or_error.value();
@@ -465,23 +473,17 @@ KResultOr<FlatPtr> Process::sys$madvise(Userspace<void*> address, size_t size, i
     if (set_volatile || set_nonvolatile) {
         if (!region->vmobject().is_anonymous())
             return EPERM;
+        auto& vmobject = static_cast<AnonymousVMObject&>(region->vmobject());
         bool was_purged = false;
-        switch (region->set_volatile(VirtualAddress(address), size, set_volatile, was_purged)) {
+        auto result = vmobject.set_volatile(set_volatile, was_purged);
-        case Region::SetVolatileError::Success:
+        if (result.is_error())
-            break;
+            return result.error();
-        case Region::SetVolatileError::NotPurgeable:
+        return was_purged ? 1 : 0;
-            return EPERM;
-        case Region::SetVolatileError::OutOfMemory:
-            return ENOMEM;
-        }
-        if (set_nonvolatile)
-            return was_purged ? 1 : 0;
-        return 0;
     }
     if (advice & MADV_GET_VOLATILE) {
         if (!region->vmobject().is_anonymous())
             return EPERM;
-        return region->is_volatile(VirtualAddress(address), size) ? 0 : 1;
+        return static_cast<AnonymousVMObject&>(region->vmobject()).is_volatile() ? 0 : 1;
     }
     return EINVAL;
 }
@@ -668,5 +670,4 @@ KResultOr<FlatPtr> Process::sys$msyscall(Userspace<void*> address)
     region->set_syscall_region(true);
     return 0;
 }
-
 }

Kernel/Syscalls/purge.cpp

@@ -19,7 +19,7 @@ KResultOr<FlatPtr> Process::sys$purge(int mode)
     REQUIRE_NO_PROMISES;
     if (!is_superuser())
         return EPERM;
-    int purged_page_count = 0;
+    size_t purged_page_count = 0;
     if (mode & PURGE_ALL_VOLATILE) {
         NonnullRefPtrVector<AnonymousVMObject> vmobjects;
         {

Kernel/UnixTypes.h

@@ -92,6 +92,7 @@ enum {
 #define MAP_STACK 0x40
 #define MAP_NORESERVE 0x80
 #define MAP_RANDOMIZED 0x100
+#define MAP_PURGEABLE 0x200
 
 #define PROT_READ 0x1
 #define PROT_WRITE 0x2

Kernel/VM/AnonymousVMObject.cpp

@@ -22,16 +22,17 @@ RefPtr<VMObject> AnonymousVMObject::try_clone()
     // commit the number of pages that we need to potentially allocate
     // so that the parent is still guaranteed to be able to have all
     // non-volatile memory available.
-    size_t need_cow_pages = 0;
+    size_t new_cow_pages_needed = 0;
 
-    // We definitely need to commit non-volatile areas
+    if (is_volatile()) {
-    for_each_nonvolatile_range([&](VolatilePageRange const& nonvolatile_range) {
+        // NOTE: If this object is currently volatile, we don't own any committed pages.
-        need_cow_pages += nonvolatile_range.count;
+    } else {
-    });
+        new_cow_pages_needed = page_count();
+    }
 
-    dbgln_if(COMMIT_DEBUG, "Cloning {:p}, need {} committed cow pages", this, need_cow_pages);
+    dbgln_if(COMMIT_DEBUG, "Cloning {:p}, need {} committed cow pages", this, new_cow_pages_needed);
 
-    if (!MM.commit_user_physical_pages(need_cow_pages))
+    if (!MM.commit_user_physical_pages(new_cow_pages_needed))
         return {};
 
     // Create or replace the committed cow pages. When cloning a previously
@@ -40,10 +41,10 @@ RefPtr<VMObject> AnonymousVMObject::try_clone()
     // one would keep the one it still has. This ensures that the original
     // one and this one, as well as the clone have sufficient resources
     // to cow all pages as needed
-    m_shared_committed_cow_pages = try_create<CommittedCowPages>(need_cow_pages);
+    m_shared_committed_cow_pages = try_create<CommittedCowPages>(new_cow_pages_needed);
 
     if (!m_shared_committed_cow_pages) {
-        MM.uncommit_user_physical_pages(need_cow_pages);
+        MM.uncommit_user_physical_pages(new_cow_pages_needed);
         return {};
     }
 
@@ -65,6 +66,20 @@ RefPtr<AnonymousVMObject> AnonymousVMObject::try_create_with_size(size_t size, A
     return adopt_ref_if_nonnull(new (nothrow) AnonymousVMObject(size, commit));
 }
 
+RefPtr<AnonymousVMObject> AnonymousVMObject::try_create_purgeable_with_size(size_t size, AllocationStrategy commit)
+{
+    if (commit == AllocationStrategy::Reserve || commit == AllocationStrategy::AllocateNow) {
+        // We need to attempt to commit before actually creating the object
+        if (!MM.commit_user_physical_pages(ceil_div(size, static_cast<size_t>(PAGE_SIZE))))
+            return {};
+    }
+    auto vmobject = adopt_ref_if_nonnull(new (nothrow) AnonymousVMObject(size, commit));
+    if (!vmobject)
+        return {};
+    vmobject->m_purgeable = true;
+    return vmobject;
+}
+
 RefPtr<AnonymousVMObject> AnonymousVMObject::try_create_with_physical_pages(Span<NonnullRefPtr<PhysicalPage>> physical_pages)
 {
     return adopt_ref_if_nonnull(new (nothrow) AnonymousVMObject(physical_pages));
@@ -81,7 +96,6 @@ RefPtr<AnonymousVMObject> AnonymousVMObject::try_create_for_physical_range(Physi
 
 AnonymousVMObject::AnonymousVMObject(size_t size, AllocationStrategy strategy)
     : VMObject(size)
-    , m_volatile_ranges_cache({ 0, page_count() })
     , m_unused_committed_pages(strategy == AllocationStrategy::Reserve ? page_count() : 0)
 {
     if (strategy == AllocationStrategy::AllocateNow) {
@@ -97,7 +111,6 @@ AnonymousVMObject::AnonymousVMObject(size_t size, AllocationStrategy strategy)
 
 AnonymousVMObject::AnonymousVMObject(PhysicalAddress paddr, size_t size)
     : VMObject(size)
-    , m_volatile_ranges_cache({ 0, page_count() })
 {
     VERIFY(paddr.page_base() == paddr);
     for (size_t i = 0; i < page_count(); ++i)
@@ -106,7 +119,6 @@ AnonymousVMObject::AnonymousVMObject(PhysicalAddress paddr, size_t size)
 
 AnonymousVMObject::AnonymousVMObject(Span<NonnullRefPtr<PhysicalPage>> physical_pages)
     : VMObject(physical_pages.size() * PAGE_SIZE)
-    , m_volatile_ranges_cache({ 0, page_count() })
 {
     for (size_t i = 0; i < physical_pages.size(); ++i) {
         m_physical_pages[i] = physical_pages[i];
@@ -115,9 +127,6 @@ AnonymousVMObject::AnonymousVMObject(Span<NonnullRefPtr<PhysicalPage>> physical_
 
 AnonymousVMObject::AnonymousVMObject(AnonymousVMObject const& other)
     : VMObject(other)
-    , m_volatile_ranges_cache({ 0, page_count() }) // do *not* clone this
-    , m_volatile_ranges_cache_dirty(true)          // do *not* clone this
-    , m_purgeable_ranges()                         // do *not* clone this
     , m_unused_committed_pages(other.m_unused_committed_pages)
     , m_cow_map()                                                      // do *not* clone this
     , m_shared_committed_cow_pages(other.m_shared_committed_cow_pages) // share the pool
@@ -152,217 +161,94 @@ AnonymousVMObject::~AnonymousVMObject()
         MM.uncommit_user_physical_pages(m_unused_committed_pages);
 }
 
-int AnonymousVMObject::purge()
+size_t AnonymousVMObject::purge()
-{
-    int purged_page_count = 0;
-    ScopedSpinLock lock(m_lock);
-    for_each_volatile_range([&](auto const& range) {
-        int purged_in_range = 0;
-        auto range_end = range.base + range.count;
-        for (size_t i = range.base; i < range_end; i++) {
-            auto& phys_page = m_physical_pages[i];
-            if (phys_page && !phys_page->is_shared_zero_page()) {
-                VERIFY(!phys_page->is_lazy_committed_page());
-                ++purged_in_range;
-            }
-            phys_page = MM.shared_zero_page();
-        }
-
-        if (purged_in_range > 0) {
-            purged_page_count += purged_in_range;
-            set_was_purged(range);
-            for_each_region([&](auto& region) {
-                if (auto owner = region.get_owner()) {
-                    // we need to hold a reference the process here (if there is one) as we may not own this region
-                    dmesgln("Purged {} pages from region {} owned by {} at {} - {}",
-                        purged_in_range,
-                        region.name(),
-                        *owner,
-                        region.vaddr_from_page_index(range.base),
-                        region.vaddr_from_page_index(range.base + range.count));
-                } else {
-                    dmesgln("Purged {} pages from region {} (no ownership) at {} - {}",
-                        purged_in_range,
-                        region.name(),
-                        region.vaddr_from_page_index(range.base),
-                        region.vaddr_from_page_index(range.base + range.count));
-                }
-                region.remap_vmobject_page_range(range.base, range.count);
-            });
-        }
-    });
-    return purged_page_count;
-}
-
-void AnonymousVMObject::set_was_purged(VolatilePageRange const& range)
-{
-    VERIFY(m_lock.is_locked());
-    for (auto* purgeable_ranges : m_purgeable_ranges)
-        purgeable_ranges->set_was_purged(range);
-}
-
-void AnonymousVMObject::register_purgeable_page_ranges(PurgeablePageRanges& purgeable_page_ranges)
 {
     ScopedSpinLock lock(m_lock);
-    purgeable_page_ranges.set_vmobject(this);
-    VERIFY(!m_purgeable_ranges.contains_slow(&purgeable_page_ranges));
-    m_purgeable_ranges.append(&purgeable_page_ranges);
-}
 
-void AnonymousVMObject::unregister_purgeable_page_ranges(PurgeablePageRanges& purgeable_page_ranges)
+    if (!is_purgeable() || !is_volatile())
-{
+        return 0;
-    ScopedSpinLock lock(m_lock);
+
-    for (size_t i = 0; i < m_purgeable_ranges.size(); i++) {
+    size_t total_pages_purged = 0;
-        if (m_purgeable_ranges[i] != &purgeable_page_ranges)
+
+    for (auto& page : m_physical_pages) {
+        VERIFY(page);
+        if (page->is_shared_zero_page())
             continue;
-        purgeable_page_ranges.set_vmobject(nullptr);
+        page = MM.shared_zero_page();
-        m_purgeable_ranges.remove(i);
+        ++total_pages_purged;
-        return;
     }
-    VERIFY_NOT_REACHED();
-}
 
-bool AnonymousVMObject::is_any_volatile() const
+    m_was_purged = true;
-{
-    ScopedSpinLock lock(m_lock);
-    for (auto& volatile_ranges : m_purgeable_ranges) {
-        ScopedSpinLock lock(volatile_ranges->m_volatile_ranges_lock);
-        if (!volatile_ranges->is_empty())
-            return true;
-    }
-    return false;
-}
 
-size_t AnonymousVMObject::remove_lazy_commit_pages(VolatilePageRange const& range)
+    for_each_region([](Region& region) {
-{
+        region.remap();
-    VERIFY(m_lock.is_locked());
-
-    size_t removed_count = 0;
-    auto range_end = range.base + range.count;
-    for (size_t i = range.base; i < range_end; i++) {
-        auto& phys_page = m_physical_pages[i];
-        if (phys_page && phys_page->is_lazy_committed_page()) {
-            phys_page = MM.shared_zero_page();
-            removed_count++;
-            VERIFY(m_unused_committed_pages > 0);
-            if (--m_unused_committed_pages == 0)
-                break;
-        }
-    }
-    return removed_count;
-}
-
-void AnonymousVMObject::update_volatile_cache()
-{
-    VERIFY(m_lock.is_locked());
-    VERIFY(m_volatile_ranges_cache_dirty);
-
-    m_volatile_ranges_cache.clear();
-    for_each_nonvolatile_range([&](VolatilePageRange const& range) {
-        m_volatile_ranges_cache.add_unchecked(range);
     });
 
-    m_volatile_ranges_cache_dirty = false;
+    return total_pages_purged;
 }
 
-void AnonymousVMObject::range_made_volatile(VolatilePageRange const& range)
+KResult AnonymousVMObject::set_volatile(bool is_volatile, bool& was_purged)
 {
-    VERIFY(m_lock.is_locked());
+    VERIFY(is_purgeable());
 
-    if (m_unused_committed_pages == 0)
+    ScopedSpinLock locker(m_lock);
-        return;
 
-    // We need to check this range for any pages that are marked for
+    was_purged = m_was_purged;
-    // lazy committed allocation and turn them into shared zero pages
+    if (m_volatile == is_volatile)
-    // and also adjust the m_unused_committed_pages for each such page.
+        return KSuccess;
-    // Take into account all the other views as well.
+
-    size_t uncommit_page_count = 0;
+    if (is_volatile) {
-    for_each_volatile_range([&](auto const& r) {
+        // When a VMObject is made volatile, it gives up all of its committed memory.
-        auto intersected = range.intersected(r);
+        // Any physical pages already allocated remain in the VMObject for now, but the kernel is free to take them at any moment.
-        if (!intersected.is_empty()) {
+        for (auto& page : m_physical_pages) {
-            uncommit_page_count += remove_lazy_commit_pages(intersected);
+            if (page && page->is_lazy_committed_page())
-            if (m_unused_committed_pages == 0)
+                page = MM.shared_zero_page();
-                return IterationDecision::Break;
         }
-        return IterationDecision::Continue;
-    });
 
-    // Return those committed pages back to the system
+        if (m_unused_committed_pages) {
-    if (uncommit_page_count > 0) {
+            MM.uncommit_user_physical_pages(m_unused_committed_pages);
-        dbgln_if(COMMIT_DEBUG, "Uncommit {} lazy-commit pages from {:p}", uncommit_page_count, this);
+            m_unused_committed_pages = 0;
-        MM.uncommit_user_physical_pages(uncommit_page_count);
-    }
-
-    m_volatile_ranges_cache_dirty = true;
-}
-
-void AnonymousVMObject::range_made_nonvolatile(VolatilePageRange const&)
-{
-    VERIFY(m_lock.is_locked());
-    m_volatile_ranges_cache_dirty = true;
-}
-
-size_t AnonymousVMObject::count_needed_commit_pages_for_nonvolatile_range(VolatilePageRange const& range)
-{
-    VERIFY(m_lock.is_locked());
-    VERIFY(!range.is_empty());
-
-    size_t need_commit_pages = 0;
-    auto range_end = range.base + range.count;
-    for (size_t page_index = range.base; page_index < range_end; page_index++) {
-        // COW pages are accounted for in m_shared_committed_cow_pages
-        if (!m_cow_map.is_null() && m_cow_map.get(page_index))
-            continue;
-        auto& phys_page = m_physical_pages[page_index];
-        if (phys_page && phys_page->is_shared_zero_page())
-            need_commit_pages++;
-    }
-    return need_commit_pages;
-}
-
-size_t AnonymousVMObject::mark_committed_pages_for_nonvolatile_range(VolatilePageRange const& range, size_t mark_total)
-{
-    VERIFY(m_lock.is_locked());
-    VERIFY(!range.is_empty());
-    VERIFY(mark_total > 0);
-
-    size_t pages_updated = 0;
-    auto range_end = range.base + range.count;
-    for (size_t page_index = range.base; page_index < range_end; page_index++) {
-        // COW pages are accounted for in m_shared_committed_cow_pages
-        if (!m_cow_map.is_null() && m_cow_map.get(page_index))
-            continue;
-        auto& phys_page = m_physical_pages[page_index];
-        if (phys_page && phys_page->is_shared_zero_page()) {
-            phys_page = MM.lazy_committed_page();
-            if (++pages_updated == mark_total)
-                break;
         }
+
+        m_volatile = true;
+        m_was_purged = false;
+        return KSuccess;
+    }
+    // When a VMObject is made non-volatile, we try to commit however many pages are not currently available.
+    // If that fails, we return false to indicate that memory allocation failed.
+    size_t committed_pages_needed = 0;
+    for (auto& page : m_physical_pages) {
+        VERIFY(page);
+        if (page->is_shared_zero_page())
+            ++committed_pages_needed;
     }
 
-    dbgln_if(COMMIT_DEBUG, "Added {} lazy-commit pages to {:p}", pages_updated, this);
+    if (!committed_pages_needed) {
+        m_volatile = false;
+        return KSuccess;
+    }
 
-    m_unused_committed_pages += pages_updated;
+    if (!MM.commit_user_physical_pages(committed_pages_needed))
-    return pages_updated;
+        return ENOMEM;
+
+    m_unused_committed_pages = committed_pages_needed;
+
+    for (auto& page : m_physical_pages) {
+        if (page->is_shared_zero_page())
+            page = MM.lazy_committed_page();
+    }
+
+    m_volatile = false;
+    m_was_purged = false;
+    return KSuccess;
 }
 
-NonnullRefPtr<PhysicalPage> AnonymousVMObject::allocate_committed_page(Badge<Region>, size_t page_index)
+NonnullRefPtr<PhysicalPage> AnonymousVMObject::allocate_committed_page(Badge<Region>)
 {
     {
         ScopedSpinLock lock(m_lock);
-
         VERIFY(m_unused_committed_pages > 0);
-
+        --m_unused_committed_pages;
-        // We shouldn't have any committed page tags in volatile regions
-        VERIFY([&]() {
-            for (auto* purgeable_ranges : m_purgeable_ranges) {
-                if (purgeable_ranges->is_volatile(page_index))
-                    return false;
-            }
-            return true;
-        }());
-
-        m_unused_committed_pages--;
     }
     return MM.allocate_committed_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
 }
@@ -404,19 +290,20 @@ size_t AnonymousVMObject::cow_pages() const
     return m_cow_map.count_slow(true);
 }
 
-bool AnonymousVMObject::is_nonvolatile(size_t page_index)
-{
-    if (m_volatile_ranges_cache_dirty)
-        update_volatile_cache();
-    return !m_volatile_ranges_cache.contains(page_index);
-}
-
 PageFaultResponse AnonymousVMObject::handle_cow_fault(size_t page_index, VirtualAddress vaddr)
 {
     VERIFY_INTERRUPTS_DISABLED();
     ScopedSpinLock lock(m_lock);
+
+    if (is_volatile()) {
+        // A COW fault in a volatile region? Userspace is writing to volatile memory, this is a bug. Crash.
+        dbgln("COW fault in volatile region, will crash.");
+        return PageFaultResponse::ShouldCrash;
+    }
+
     auto& page_slot = physical_pages()[page_index];
-    bool have_committed = m_shared_committed_cow_pages && is_nonvolatile(page_index);
+    bool have_committed = m_shared_committed_cow_pages;
+
     if (page_slot->ref_count() == 1) {
         dbgln_if(PAGE_FAULT_DEBUG, "    >> It's a COW page but nobody is sharing it anymore. Remap r/w");
         set_should_cow(page_index, false);
@@ -462,4 +349,33 @@ PageFaultResponse AnonymousVMObject::handle_cow_fault(size_t page_index, Virtual
     return PageFaultResponse::Continue;
 }
 
+CommittedCowPages::CommittedCowPages(size_t committed_pages)
+    : m_committed_pages(committed_pages)
+{
+}
+
+CommittedCowPages::~CommittedCowPages()
+{
+    // Return unused committed pages
+    if (m_committed_pages > 0)
+        MM.uncommit_user_physical_pages(m_committed_pages);
+}
+
+NonnullRefPtr<PhysicalPage> CommittedCowPages::allocate_one()
+{
+    VERIFY(m_committed_pages > 0);
+    m_committed_pages--;
+
+    return MM.allocate_committed_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
+}
+
+bool CommittedCowPages::return_one()
+{
+    VERIFY(m_committed_pages > 0);
+    m_committed_pages--;
+
+    MM.uncommit_user_physical_pages(1);
+    return m_committed_pages == 0;
+}
+
 }

Kernel/VM/AnonymousVMObject.h

@@ -10,108 +10,48 @@
 #include <Kernel/VM/AllocationStrategy.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/PageFaultResponse.h>
-#include <Kernel/VM/PurgeablePageRanges.h>
 #include <Kernel/VM/VMObject.h>
 
 namespace Kernel {
 
-class AnonymousVMObject final : public VMObject {
+class CommittedCowPages : public RefCounted<CommittedCowPages> {
-    friend class PurgeablePageRanges;
+    AK_MAKE_NONCOPYABLE(CommittedCowPages);
 
+public:
+    CommittedCowPages() = delete;
+
+    CommittedCowPages(size_t);
+    ~CommittedCowPages();
+
+    NonnullRefPtr<PhysicalPage> allocate_one();
+    bool return_one();
+
+private:
+    size_t m_committed_pages;
+};
+
+class AnonymousVMObject final : public VMObject {
 public:
     virtual ~AnonymousVMObject() override;
 
     static RefPtr<AnonymousVMObject> try_create_with_size(size_t, AllocationStrategy);
     static RefPtr<AnonymousVMObject> try_create_for_physical_range(PhysicalAddress paddr, size_t size);
     static RefPtr<AnonymousVMObject> try_create_with_physical_pages(Span<NonnullRefPtr<PhysicalPage>>);
+    static RefPtr<AnonymousVMObject> try_create_purgeable_with_size(size_t, AllocationStrategy);
     virtual RefPtr<VMObject> try_clone() override;
 
-    [[nodiscard]] NonnullRefPtr<PhysicalPage> allocate_committed_page(Badge<Region>, size_t);
+    [[nodiscard]] NonnullRefPtr<PhysicalPage> allocate_committed_page(Badge<Region>);
     PageFaultResponse handle_cow_fault(size_t, VirtualAddress);
     size_t cow_pages() const;
     bool should_cow(size_t page_index, bool) const;
     void set_should_cow(size_t page_index, bool);
 
-    void register_purgeable_page_ranges(PurgeablePageRanges&);
+    bool is_purgeable() const { return m_purgeable; }
-    void unregister_purgeable_page_ranges(PurgeablePageRanges&);
+    bool is_volatile() const { return m_volatile; }
 
-    int purge();
+    KResult set_volatile(bool is_volatile, bool& was_purged);
 
-    bool is_any_volatile() const;
+    size_t purge();
-
-    template<IteratorFunction<VolatilePageRange const&> F>
-    IterationDecision for_each_volatile_range(F f) const
-    {
-        VERIFY(m_lock.is_locked());
-        // This is a little ugly. Basically, we're trying to find the
-        // volatile ranges that all share, because those are the only
-        // pages we can actually purge
-        for (auto* purgeable_range : m_purgeable_ranges) {
-            ScopedSpinLock purgeable_lock(purgeable_range->m_volatile_ranges_lock);
-            for (auto& r1 : purgeable_range->volatile_ranges().ranges()) {
-                VolatilePageRange range(r1);
-                for (auto* purgeable_range2 : m_purgeable_ranges) {
-                    if (purgeable_range2 == purgeable_range)
-                        continue;
-                    ScopedSpinLock purgeable2_lock(purgeable_range2->m_volatile_ranges_lock);
-                    if (purgeable_range2->is_empty()) {
-                        // If just one doesn't allow any purging, we can
-                        // immediately bail
-                        return IterationDecision::Continue;
-                    }
-                    for (auto const& r2 : purgeable_range2->volatile_ranges().ranges()) {
-                        range = range.intersected(r2);
-                        if (range.is_empty())
-                            break;
-                    }
-                    if (range.is_empty())
-                        break;
-                }
-                if (range.is_empty())
-                    continue;
-                IterationDecision decision = f(range);
-                if (decision != IterationDecision::Continue)
-                    return decision;
-            }
-        }
-        return IterationDecision::Continue;
-    }
-
-    template<IteratorFunction<VolatilePageRange const&> F>
-    IterationDecision for_each_nonvolatile_range(F f) const
-    {
-        size_t base = 0;
-        for_each_volatile_range([&](VolatilePageRange const& volatile_range) {
-            if (volatile_range.base == base)
-                return IterationDecision::Continue;
-            IterationDecision decision = f(VolatilePageRange { base, volatile_range.base - base });
-            if (decision != IterationDecision::Continue)
-                return decision;
-            base = volatile_range.base + volatile_range.count;
-            return IterationDecision::Continue;
-        });
-        if (base < page_count())
-            return f(VolatilePageRange { base, page_count() - base });
-        return IterationDecision::Continue;
-    }
-
-    template<VoidFunction<VolatilePageRange const&> F>
-    IterationDecision for_each_volatile_range(F f) const
-    {
-        return for_each_volatile_range([&](auto& range) {
-            f(range);
-            return IterationDecision::Continue;
-        });
-    }
-
-    template<VoidFunction<VolatilePageRange const&> F>
-    IterationDecision for_each_nonvolatile_range(F f) const
-    {
-        return for_each_nonvolatile_range([&](auto range) {
-            f(move(range));
-            return IterationDecision::Continue;
-        });
-    }
 
 private:
     explicit AnonymousVMObject(size_t, AllocationStrategy);
@@ -121,15 +61,6 @@ private:
 
     virtual StringView class_name() const override { return "AnonymousVMObject"sv; }
 
-    void update_volatile_cache();
-    void set_was_purged(VolatilePageRange const&);
-    size_t remove_lazy_commit_pages(VolatilePageRange const&);
-    void range_made_volatile(VolatilePageRange const&);
-    void range_made_nonvolatile(VolatilePageRange const&);
-    size_t count_needed_commit_pages_for_nonvolatile_range(VolatilePageRange const&);
-    size_t mark_committed_pages_for_nonvolatile_range(VolatilePageRange const&, size_t);
-    bool is_nonvolatile(size_t page_index);
-
     AnonymousVMObject& operator=(AnonymousVMObject const&) = delete;
     AnonymousVMObject& operator=(AnonymousVMObject&&) = delete;
     AnonymousVMObject(AnonymousVMObject&&) = delete;
@@ -139,15 +70,15 @@ private:
     Bitmap& ensure_cow_map();
     void ensure_or_reset_cow_map();
 
-    VolatilePageRanges m_volatile_ranges_cache;
-    bool m_volatile_ranges_cache_dirty { true };
-    Vector<PurgeablePageRanges*> m_purgeable_ranges;
     size_t m_unused_committed_pages { 0 };
-
     Bitmap m_cow_map;
 
     // We share a pool of committed cow-pages with clones
     RefPtr<CommittedCowPages> m_shared_committed_cow_pages;
+
+    bool m_purgeable { false };
+    bool m_volatile { false };
+    bool m_was_purged { false };
 };
 
 }

Kernel/VM/PurgeablePageRanges.cpp

@@ -1,310 +0,0 @@
-/*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <AK/BinarySearch.h>
-#include <AK/ScopeGuard.h>
-#include <Kernel/Debug.h>
-#include <Kernel/Process.h>
-#include <Kernel/VM/AnonymousVMObject.h>
-#include <Kernel/VM/MemoryManager.h>
-#include <Kernel/VM/PhysicalPage.h>
-#include <Kernel/VM/PurgeablePageRanges.h>
-
-namespace AK {
-template<>
-struct Formatter<Kernel::VolatilePageRange> : Formatter<String> {
-    void format(FormatBuilder& builder, const Kernel::VolatilePageRange& value)
-    {
-        return Formatter<String>::format(builder, String::formatted("{{{} ({}) purged: {}}}", value.base, value.count, value.was_purged));
-    }
-};
-}
-
-namespace Kernel {
-
-static void dump_volatile_page_ranges(const Vector<VolatilePageRange>& ranges)
-{
-    if constexpr (VOLATILE_PAGE_RANGES_DEBUG) {
-        for (size_t i = 0; i < ranges.size(); i++) {
-            dbgln("[{}] {}", i, ranges[i]);
-        }
-    }
-}
-
-void VolatilePageRanges::add_unchecked(const VolatilePageRange& range)
-{
-    auto add_range = m_total_range.intersected(range);
-    if (add_range.is_empty())
-        return;
-    m_ranges.append(range);
-}
-
-bool VolatilePageRanges::add(const VolatilePageRange& range)
-{
-    auto add_range = m_total_range.intersected(range);
-    if (add_range.is_empty())
-        return false;
-    add_range.was_purged = range.was_purged;
-
-    if constexpr (VOLATILE_PAGE_RANGES_DEBUG) {
-        dbgln("ADD {} (total range: {}) -->", range, m_total_range);
-        dump_volatile_page_ranges(m_ranges);
-        ScopeGuard debug_guard([&]() {
-            dbgln("After adding {} (total range: {})", range, m_total_range);
-            dump_volatile_page_ranges(m_ranges);
-            dbgln("<-- ADD {} (total range: {})", range, m_total_range);
-        });
-    }
-
-    size_t nearby_index = 0;
-    auto* existing_range = binary_search(
-        m_ranges.span(), add_range, &nearby_index, [](auto& a, auto& b) {
-            if (a.intersects_or_adjacent(b))
-                return 0;
-            return (signed)(a.base - (b.base + b.count - 1));
-        });
-
-    size_t inserted_index = 0;
-    if (existing_range) {
-        if (*existing_range == add_range)
-            return false;
-
-        if (existing_range->was_purged != add_range.was_purged) {
-            // Found an intersecting or adjacent range, but the purge flag
-            // doesn't match. Subtract what we're adding from it, and
-            existing_range->subtract_intersecting(add_range);
-            if (existing_range->is_empty()) {
-                *existing_range = add_range;
-            } else {
-                m_ranges.insert(++nearby_index, add_range);
-                existing_range = &m_ranges[nearby_index];
-            }
-        } else {
-            // Found an intersecting or adjacent range that can be merged
-            existing_range->combine_intersecting_or_adjacent(add_range);
-        }
-        inserted_index = nearby_index;
-    } else {
-        // Insert into the sorted list
-        m_ranges.insert_before_matching(
-            VolatilePageRange(add_range), [&](auto& entry) {
-                return entry.base >= add_range.base + add_range.count;
-            },
-            nearby_index, &inserted_index);
-        existing_range = &m_ranges[inserted_index];
-    }
-
-    // See if we can merge any of the following ranges
-    inserted_index++;
-    while (inserted_index < m_ranges.size()) {
-        auto& next_range = m_ranges[inserted_index];
-        if (!next_range.intersects_or_adjacent(*existing_range))
-            break;
-        if (next_range.was_purged != existing_range->was_purged) {
-            // The purged flag of following range is not the same.
-            // Subtract the added/combined range from it
-            next_range.subtract_intersecting(*existing_range);
-            if (next_range.is_empty())
-                m_ranges.remove(inserted_index);
-        } else {
-            existing_range->combine_intersecting_or_adjacent(next_range);
-            m_ranges.remove(inserted_index);
-        }
-    }
-    return true;
-}
-
-bool VolatilePageRanges::remove(const VolatilePageRange& range, bool& was_purged)
-{
-    auto remove_range = m_total_range.intersected(range);
-    if (remove_range.is_empty())
-        return false;
-
-    if constexpr (VOLATILE_PAGE_RANGES_DEBUG) {
-        dbgln("REMOVE {} (total range: {}) -->", range, m_total_range);
-        dump_volatile_page_ranges(m_ranges);
-        ScopeGuard debug_guard([&]() {
-            dbgln("After removing {} (total range: {})", range, m_total_range);
-            dump_volatile_page_ranges(m_ranges);
-            dbgln("<-- REMOVE {} (total range: {}) was_purged: {}", range, m_total_range, was_purged);
-        });
-    }
-
-    size_t nearby_index = 0;
-    auto* existing_range = binary_search(
-        m_ranges.span(), remove_range, &nearby_index, [](auto& a, auto& b) {
-            if (a.intersects(b))
-                return 0;
-            return (signed)(a.base - (b.base + b.count - 1));
-        });
-    if (!existing_range)
-        return false;
-
-    was_purged = existing_range->was_purged;
-    if (existing_range->range_equals(remove_range)) {
-        m_ranges.remove(nearby_index);
-    } else {
-        // See if we need to remove any of the following ranges
-        VERIFY(existing_range == &m_ranges[nearby_index]); // sanity check
-        while (nearby_index < m_ranges.size()) {
-            existing_range = &m_ranges[nearby_index];
-            if (!existing_range->intersects(range))
-                break;
-            was_purged |= existing_range->was_purged;
-            existing_range->subtract_intersecting(remove_range);
-            if (existing_range->is_empty()) {
-                m_ranges.remove(nearby_index);
-                break;
-            }
-        }
-    }
-    return true;
-}
-
-bool VolatilePageRanges::intersects(const VolatilePageRange& range) const
-{
-    auto* existing_range = binary_search(
-        m_ranges.span(), range, nullptr, [](auto& a, auto& b) {
-            if (a.intersects(b))
-                return 0;
-            return (signed)(a.base - (b.base + b.count - 1));
-        });
-    return existing_range != nullptr;
-}
-
-PurgeablePageRanges::PurgeablePageRanges(const VMObject& vmobject)
-    : m_volatile_ranges({ 0, vmobject.is_anonymous() ? vmobject.page_count() : 0 })
-{
-}
-
-bool PurgeablePageRanges::add_volatile_range(const VolatilePageRange& range)
-{
-    if (range.is_empty())
-        return false;
-
-    // Since we may need to call into AnonymousVMObject we need to acquire
-    // its lock as well, and acquire it first. This is important so that
-    // we don't deadlock when a page fault (e.g. on another processor)
-    // happens that is meant to lazy-allocate a committed page. It would
-    // call into AnonymousVMObject::range_made_volatile, which then would
-    // also call into this object and need to acquire m_lock. By acquiring
-    // the vmobject lock first in both cases, we avoid deadlocking.
-    // We can access m_vmobject without any locks for that purpose because
-    // add_volatile_range and remove_volatile_range can only be called
-    // by same object that calls set_vmobject.
-    ScopedSpinLock vmobject_lock(m_vmobject->m_lock);
-    ScopedSpinLock lock(m_volatile_ranges_lock);
-    bool added = m_volatile_ranges.add(range);
-    if (added)
-        m_vmobject->range_made_volatile(range);
-    return added;
-}
-
-auto PurgeablePageRanges::remove_volatile_range(const VolatilePageRange& range, bool& was_purged) -> RemoveVolatileError
-{
-    if (range.is_empty()) {
-        was_purged = false;
-        return RemoveVolatileError::Success;
-    }
-    ScopedSpinLock vmobject_lock(m_vmobject->m_lock); // see comment in add_volatile_range
-    ScopedSpinLock lock(m_volatile_ranges_lock);
-    VERIFY(m_vmobject);
-
-    // Before we actually remove this range, we need to check if we need
-    // to commit any pages, which may fail. If it fails, we don't actually
-    // want to make any modifications. COW pages are already accounted for
-    // in m_shared_committed_cow_pages
-    size_t need_commit_pages = 0;
-    m_volatile_ranges.for_each_intersecting_range(range, [&](const VolatilePageRange& intersected_range) {
-        need_commit_pages += m_vmobject->count_needed_commit_pages_for_nonvolatile_range(intersected_range);
-        return IterationDecision::Continue;
-    });
-    if (need_commit_pages > 0) {
-        // See if we can grab enough pages for what we're marking non-volatile
-        if (!MM.commit_user_physical_pages(need_commit_pages))
-            return RemoveVolatileError::OutOfMemory;
-
-        // Now that we are committed to these pages, mark them for lazy-commit allocation
-        auto pages_to_mark = need_commit_pages;
-        m_volatile_ranges.for_each_intersecting_range(range, [&](const VolatilePageRange& intersected_range) {
-            auto pages_marked = m_vmobject->mark_committed_pages_for_nonvolatile_range(intersected_range, pages_to_mark);
-            pages_to_mark -= pages_marked;
-            return IterationDecision::Continue;
-        });
-    }
-
-    // Now actually remove the range
-    if (m_volatile_ranges.remove(range, was_purged)) {
-        m_vmobject->range_made_nonvolatile(range);
-        return RemoveVolatileError::Success;
-    }
-
-    VERIFY(need_commit_pages == 0); // We should have not touched anything
-    return RemoveVolatileError::SuccessNoChange;
-}
-
-bool PurgeablePageRanges::is_volatile_range(const VolatilePageRange& range) const
-{
-    if (range.is_empty())
-        return false;
-    ScopedSpinLock lock(m_volatile_ranges_lock);
-    return m_volatile_ranges.intersects(range);
-}
-
-bool PurgeablePageRanges::is_volatile(size_t index) const
-{
-    ScopedSpinLock lock(m_volatile_ranges_lock);
-    return m_volatile_ranges.contains(index);
-}
-
-void PurgeablePageRanges::set_was_purged(const VolatilePageRange& range)
-{
-    ScopedSpinLock lock(m_volatile_ranges_lock);
-    m_volatile_ranges.add({ range.base, range.count, true });
-}
-
-void PurgeablePageRanges::set_vmobject(AnonymousVMObject* vmobject)
-{
-    // No lock needed here
-    if (vmobject) {
-        VERIFY(!m_vmobject);
-        m_vmobject = vmobject;
-    } else {
-        VERIFY(m_vmobject);
-        m_vmobject = nullptr;
-    }
-}
-
-CommittedCowPages::CommittedCowPages(size_t committed_pages)
-    : m_committed_pages(committed_pages)
-{
-}
-
-CommittedCowPages::~CommittedCowPages()
-{
-    // Return unused committed pages
-    if (m_committed_pages > 0)
-        MM.uncommit_user_physical_pages(m_committed_pages);
-}
-
-NonnullRefPtr<PhysicalPage> CommittedCowPages::allocate_one()
-{
-    VERIFY(m_committed_pages > 0);
-    m_committed_pages--;
-
-    return MM.allocate_committed_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
-}
-
-bool CommittedCowPages::return_one()
-{
-    VERIFY(m_committed_pages > 0);
-    m_committed_pages--;
-
-    MM.uncommit_user_physical_pages(1);
-    return m_committed_pages == 0;
-}
-
-}

Kernel/VM/PurgeablePageRanges.h

@@ -1,245 +0,0 @@
-/*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#pragma once
-
-#include <AK/Bitmap.h>
-#include <AK/RefCounted.h>
-#include <Kernel/SpinLock.h>
-
-namespace Kernel {
-
-struct VolatilePageRange {
-    size_t base { 0 };
-    size_t count { 0 };
-    bool was_purged { false };
-
-    bool is_empty() const { return count == 0; }
-
-    bool intersects(const VolatilePageRange& other) const
-    {
-        return other.base < base + count || other.base + other.count > base;
-    }
-
-    bool intersects_or_adjacent(const VolatilePageRange& other) const
-    {
-        return other.base <= base + count || other.base + other.count >= base;
-    }
-
-    bool contains(const VolatilePageRange& other) const
-    {
-        return base <= other.base && base + count >= other.base + other.count;
-    }
-
-    VolatilePageRange intersected(const VolatilePageRange& other) const
-    {
-        auto b = max(base, other.base);
-        auto e = min(base + count, other.base + other.count);
-        if (b >= e)
-            return {};
-        return { b, e - b, was_purged };
-    }
-
-    void combine_intersecting_or_adjacent(const VolatilePageRange& other)
-    {
-        VERIFY(intersects_or_adjacent(other));
-        if (base <= other.base) {
-            count = (other.base - base) + other.count;
-        } else {
-            count = (base - other.base) + count;
-            base = other.base;
-        }
-        was_purged |= other.was_purged;
-    }
-
-    void subtract_intersecting(const VolatilePageRange& other)
-    {
-        if (!intersects(other))
-            return;
-        if (other.contains(*this)) {
-            count = 0;
-            return;
-        }
-        if (base <= other.base) {
-            count = (other.base - base);
-        } else {
-            auto new_base = other.base + other.count;
-            count = (base + count) - new_base;
-            base = new_base;
-        }
-    }
-
-    bool range_equals(const VolatilePageRange& other) const
-    {
-        return base == other.base && count == other.count;
-    }
-    bool operator==(const VolatilePageRange& other) const
-    {
-        return base == other.base && count == other.count && was_purged == other.was_purged;
-    }
-    bool operator!=(const VolatilePageRange& other) const
-    {
-        return base != other.base || count != other.count || was_purged != other.was_purged;
-    }
-};
-
-class VolatilePageRanges {
-public:
-    VolatilePageRanges(const VolatilePageRange& total_range)
-        : m_total_range(total_range)
-    {
-    }
-    VolatilePageRanges(const VolatilePageRanges& other)
-        : m_ranges(other.m_ranges)
-        , m_total_range(other.m_total_range)
-    {
-    }
-
-    bool is_empty() const { return m_ranges.is_empty(); }
-    void clear() { m_ranges.clear_with_capacity(); }
-
-    bool is_all() const
-    {
-        if (m_ranges.size() != 1)
-            return false;
-        return m_ranges[0] == m_total_range;
-    }
-
-    void set_all()
-    {
-        if (m_ranges.size() != 1)
-            m_ranges = { m_total_range };
-        else
-            m_ranges[0] = m_total_range;
-    }
-
-    bool intersects(const VolatilePageRange&) const;
-    bool contains(size_t index) const
-    {
-        return intersects({ index, 1 });
-    }
-
-    bool add(const VolatilePageRange&);
-    void add_unchecked(const VolatilePageRange&);
-    bool remove(const VolatilePageRange&, bool&);
-
-    template<typename F>
-    IterationDecision for_each_intersecting_range(const VolatilePageRange& range, F f)
-    {
-        auto r = m_total_range.intersected(range);
-        if (r.is_empty())
-            return IterationDecision::Continue;
-
-        size_t nearby_index = 0;
-        auto* existing_range = binary_search(
-            m_ranges.span(), r, &nearby_index, [](auto& a, auto& b) {
-                if (a.intersects(b))
-                    return 0;
-                return (signed)(a.base - (b.base + b.count - 1));
-            });
-        if (!existing_range)
-            return IterationDecision::Continue;
-
-        if (existing_range->range_equals(r))
-            return f(r);
-        VERIFY(existing_range == &m_ranges[nearby_index]); // sanity check
-        while (nearby_index < m_ranges.size()) {
-            existing_range = &m_ranges[nearby_index];
-            if (!existing_range->intersects(range))
-                break;
-
-            IterationDecision decision = f(existing_range->intersected(r));
-            if (decision != IterationDecision::Continue)
-                return decision;
-
-            nearby_index++;
-        }
-        return IterationDecision::Continue;
-    }
-
-    template<typename F>
-    IterationDecision for_each_nonvolatile_range(F f) const
-    {
-        size_t base = m_total_range.base;
-        for (const auto& volatile_range : m_ranges) {
-            if (volatile_range.base == base)
-                continue;
-            IterationDecision decision = f({ base, volatile_range.base - base });
-            if (decision != IterationDecision::Continue)
-                return decision;
-            base = volatile_range.base + volatile_range.count;
-        }
-        if (base < m_total_range.base + m_total_range.count)
-            return f({ base, (m_total_range.base + m_total_range.count) - base });
-        return IterationDecision::Continue;
-    }
-
-    Vector<VolatilePageRange>& ranges() { return m_ranges; }
-    const Vector<VolatilePageRange>& ranges() const { return m_ranges; }
-
-private:
-    Vector<VolatilePageRange> m_ranges;
-    VolatilePageRange m_total_range;
-};
-
-class AnonymousVMObject;
-
-class PurgeablePageRanges {
-    friend class AnonymousVMObject;
-
-public:
-    PurgeablePageRanges(const VMObject&);
-
-    void copy_purgeable_page_ranges(const PurgeablePageRanges& other)
-    {
-        if (this == &other)
-            return;
-        ScopedSpinLock lock(m_volatile_ranges_lock);
-        ScopedSpinLock other_lock(other.m_volatile_ranges_lock);
-        m_volatile_ranges = other.m_volatile_ranges;
-    }
-
-    bool add_volatile_range(const VolatilePageRange& range);
-    enum class RemoveVolatileError {
-        Success = 0,
-        SuccessNoChange,
-        OutOfMemory
-    };
-    RemoveVolatileError remove_volatile_range(const VolatilePageRange& range, bool& was_purged);
-    bool is_volatile_range(const VolatilePageRange& range) const;
-    bool is_volatile(size_t) const;
-
-    bool is_empty() const { return m_volatile_ranges.is_empty(); }
-
-    void set_was_purged(const VolatilePageRange&);
-
-    const VolatilePageRanges& volatile_ranges() const { return m_volatile_ranges; }
-
-protected:
-    void set_vmobject(AnonymousVMObject*);
-
-    VolatilePageRanges m_volatile_ranges;
-    mutable RecursiveSpinLock m_volatile_ranges_lock;
-    AnonymousVMObject* m_vmobject { nullptr };
-};
-
-class CommittedCowPages : public RefCounted<CommittedCowPages> {
-    AK_MAKE_NONCOPYABLE(CommittedCowPages);
-
-public:
-    CommittedCowPages() = delete;
-
-    CommittedCowPages(size_t);
-    ~CommittedCowPages();
-
-    NonnullRefPtr<PhysicalPage> allocate_one();
-    bool return_one();
-
-private:
-    size_t m_committed_pages;
-};
-
-}

Kernel/VM/Region.cpp

@@ -20,8 +20,7 @@
 namespace Kernel {
 
 Region::Region(Range const& range, NonnullRefPtr<VMObject> vmobject, size_t offset_in_vmobject, OwnPtr<KString> name, Region::Access access, Cacheable cacheable, bool shared)
-    : PurgeablePageRanges(vmobject)
+    : m_range(range)
-    , m_range(range)
     , m_offset_in_vmobject(offset_in_vmobject)
     , m_vmobject(move(vmobject))
     , m_name(move(name))
@@ -34,14 +33,12 @@ Region::Region(Range const& range, NonnullRefPtr<VMObject> vmobject, size_t offs
     VERIFY((m_range.size() % PAGE_SIZE) == 0);
 
     m_vmobject->add_region(*this);
-    register_purgeable_page_ranges();
     MM.register_region(*this);
 }
 
 Region::~Region()
 {
     m_vmobject->remove_region(*this);
-    unregister_purgeable_page_ranges();
 
     // Make sure we disable interrupts so we don't get interrupted between unmapping and unregistering.
     // Unmapping the region will give the VM back to the RangeAllocator, so an interrupt handler would
@@ -55,22 +52,6 @@ Region::~Region()
     MM.unregister_region(*this);
 }
 
-void Region::register_purgeable_page_ranges()
-{
-    if (m_vmobject->is_anonymous()) {
-        auto& vmobject = static_cast<AnonymousVMObject&>(*m_vmobject);
-        vmobject.register_purgeable_page_ranges(*this);
-    }
-}
-
-void Region::unregister_purgeable_page_ranges()
-{
-    if (m_vmobject->is_anonymous()) {
-        auto& vmobject = static_cast<AnonymousVMObject&>(*m_vmobject);
-        vmobject.unregister_purgeable_page_ranges(*this);
-    }
-}
-
 OwnPtr<Region> Region::clone(Process& new_owner)
 {
     VERIFY(Process::current());
@@ -89,8 +70,6 @@ OwnPtr<Region> Region::clone(Process& new_owner)
             dbgln("Region::clone: Unable to allocate new Region");
             return nullptr;
         }
-        if (m_vmobject->is_anonymous())
-            region->copy_purgeable_page_ranges(*this);
         region->set_mmap(m_mmap);
         region->set_shared(m_shared);
         region->set_syscall_region(is_syscall_region());
@@ -112,8 +91,6 @@ OwnPtr<Region> Region::clone(Process& new_owner)
         dbgln("Region::clone: Unable to allocate new Region for COW");
         return nullptr;
     }
-    if (m_vmobject->is_anonymous())
-        clone_region->copy_purgeable_page_ranges(*this);
     if (m_stack) {
         VERIFY(is_readable());
         VERIFY(is_writable());
@@ -129,55 +106,9 @@ void Region::set_vmobject(NonnullRefPtr<VMObject>&& obj)
 {
     if (m_vmobject.ptr() == obj.ptr())
         return;
-    unregister_purgeable_page_ranges();
     m_vmobject->remove_region(*this);
     m_vmobject = move(obj);
     m_vmobject->add_region(*this);
-    register_purgeable_page_ranges();
-}
-
-bool Region::is_volatile(VirtualAddress vaddr, size_t size) const
-{
-    if (!m_vmobject->is_anonymous())
-        return false;
-
-    auto offset_in_vmobject = vaddr.get() - (this->vaddr().get() - m_offset_in_vmobject);
-    size_t first_page_index = page_round_down(offset_in_vmobject) / PAGE_SIZE;
-    size_t last_page_index = page_round_up(offset_in_vmobject + size) / PAGE_SIZE;
-    return is_volatile_range({ first_page_index, last_page_index - first_page_index });
-}
-
-auto Region::set_volatile(VirtualAddress vaddr, size_t size, bool is_volatile, bool& was_purged) -> SetVolatileError
-{
-    was_purged = false;
-    if (!m_vmobject->is_anonymous())
-        return SetVolatileError::NotPurgeable;
-
-    auto offset_in_vmobject = vaddr.get() - (this->vaddr().get() - m_offset_in_vmobject);
-    if (is_volatile) {
-        // If marking pages as volatile, be prudent by not marking
-        // partial pages volatile to prevent potentially non-volatile
-        // data to be discarded. So rund up the first page and round
-        // down the last page.
-        size_t first_page_index = page_round_up(offset_in_vmobject) / PAGE_SIZE;
-        size_t last_page_index = page_round_down(offset_in_vmobject + size) / PAGE_SIZE;
-        if (first_page_index != last_page_index)
-            add_volatile_range({ first_page_index, last_page_index - first_page_index });
-    } else {
-        // If marking pages as non-volatile, round down the first page
-        // and round up the last page to make sure the beginning and
-        // end of the range doesn't inadvertedly get discarded.
-        size_t first_page_index = page_round_down(offset_in_vmobject) / PAGE_SIZE;
-        size_t last_page_index = page_round_up(offset_in_vmobject + size) / PAGE_SIZE;
-        switch (remove_volatile_range({ first_page_index, last_page_index - first_page_index }, was_purged)) {
-        case PurgeablePageRanges::RemoveVolatileError::Success:
-        case PurgeablePageRanges::RemoveVolatileError::SuccessNoChange:
-            break;
-        case PurgeablePageRanges::RemoveVolatileError::OutOfMemory:
-            return SetVolatileError::OutOfMemory;
-        }
-    }
-    return SetVolatileError::Success;
 }
 
 size_t Region::cow_pages() const
@@ -279,43 +210,6 @@ bool Region::map_individual_page_impl(size_t page_index)
     return true;
 }
 
-bool Region::do_remap_vmobject_page_range(size_t page_index, size_t page_count)
-{
-    bool success = true;
-    if (!m_page_directory)
-        return success; // not an error, region may have not yet mapped it
-    if (!translate_vmobject_page_range(page_index, page_count))
-        return success; // not an error, region doesn't map this page range
-    ScopedSpinLock page_lock(m_page_directory->get_lock());
-    size_t index = page_index;
-    while (index < page_index + page_count) {
-        if (!map_individual_page_impl(index)) {
-            success = false;
-            break;
-        }
-        index++;
-    }
-    if (index > page_index)
-        MM.flush_tlb(m_page_directory, vaddr_from_page_index(page_index), index - page_index);
-    return success;
-}
-
-bool Region::remap_vmobject_page_range(size_t page_index, size_t page_count)
-{
-    bool success = true;
-    auto& vmobject = this->vmobject();
-    if (vmobject.is_shared_by_multiple_regions()) {
-        vmobject.for_each_region([&](auto& region) {
-            if (!region.do_remap_vmobject_page_range(page_index, page_count))
-                success = false;
-        });
-    } else {
-        if (!do_remap_vmobject_page_range(page_index, page_count))
-            success = false;
-    }
-    return success;
-}
-
 bool Region::do_remap_vmobject_page(size_t page_index, bool with_flush)
 {
     ScopedSpinLock lock(vmobject().m_lock);
@@ -428,7 +322,7 @@ PageFaultResponse Region::handle_fault(PageFault const& fault)
         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({}, page_index_in_vmobject);
+            page_slot = static_cast<AnonymousVMObject&>(*m_vmobject).allocate_committed_page({});
             remap_vmobject_page(page_index_in_vmobject);
             return PageFaultResponse::Continue;
         }
@@ -472,7 +366,7 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
 
     if (page_slot->is_lazy_committed_page()) {
         VERIFY(m_vmobject->is_anonymous());
-        page_slot = static_cast<AnonymousVMObject&>(*m_vmobject).allocate_committed_page({}, page_index_in_vmobject);
+        page_slot = static_cast<AnonymousVMObject&>(*m_vmobject).allocate_committed_page({});
         dbgln_if(PAGE_FAULT_DEBUG, "      >> ALLOCATED COMMITTED {}", page_slot->paddr());
     } else {
         page_slot = MM.allocate_user_physical_page(MemoryManager::ShouldZeroFill::Yes);

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 Weakable<Region> {
-    , public PurgeablePageRanges {
     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 };

Kernel/VM/Space.cpp

@@ -414,7 +414,10 @@ size_t Space::amount_purgeable_volatile() const
     ScopedSpinLock lock(m_lock);
     size_t amount = 0;
     for (auto& region : m_regions) {
-        if (region->vmobject().is_anonymous() && static_cast<const AnonymousVMObject&>(region->vmobject()).is_any_volatile())
+        if (!region->vmobject().is_anonymous())
+            continue;
+        auto const& vmobject = static_cast<AnonymousVMObject const&>(region->vmobject());
+        if (vmobject.is_purgeable() && vmobject.is_volatile())
             amount += region->amount_resident();
     }
     return amount;
@@ -425,7 +428,10 @@ size_t Space::amount_purgeable_nonvolatile() const
     ScopedSpinLock lock(m_lock);
     size_t amount = 0;
     for (auto& region : m_regions) {
-        if (region->vmobject().is_anonymous() && !static_cast<const AnonymousVMObject&>(region->vmobject()).is_any_volatile())
+        if (!region->vmobject().is_anonymous())
+            continue;
+        auto const& vmobject = static_cast<AnonymousVMObject const&>(region->vmobject());
+        if (vmobject.is_purgeable() && !vmobject.is_volatile())
             amount += region->amount_resident();
     }
     return amount;

Userland/Libraries/LibC/malloc.cpp

@@ -158,7 +158,7 @@ extern "C" {
 
 static void* os_alloc(size_t size, const char* name)
 {
-    auto* ptr = serenity_mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0, ChunkedBlock::block_size, name);
+    auto* ptr = serenity_mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_PURGEABLE, 0, 0, ChunkedBlock::block_size, name);
     VERIFY(ptr != MAP_FAILED);
     return ptr;
 }

Userland/Libraries/LibC/sys/mman.h

@@ -18,6 +18,7 @@
 #define MAP_STACK 0x40
 #define MAP_NORESERVE 0x80
 #define MAP_RANDOMIZED 0x100
+#define MAP_PURGEABLE 0x200
 
 #define PROT_READ 0x1
 #define PROT_WRITE 0x2

Userland/Libraries/LibGfx/Bitmap.cpp

@@ -544,11 +544,11 @@ void Bitmap::set_volatile()
     int rc = madvise(m_data, size_in_bytes(), MADV_SET_NONVOLATILE);
     if (rc < 0) {
         if (errno == ENOMEM) {
-            was_purged = was_purged_int;
+            was_purged = true;
             return false;
         }
-
         perror("madvise(MADV_SET_NONVOLATILE)");
+        VERIFY_NOT_REACHED();
     }
     was_purged = rc != 0;
 #endif
@@ -574,6 +574,7 @@ Optional<BackingStore> Bitmap::try_allocate_backing_store(BitmapFormat format, I
 
     int map_flags = MAP_ANONYMOUS | MAP_PRIVATE;
 #ifdef __serenity__
+    map_flags |= MAP_PURGEABLE;
     void* data = mmap_with_name(nullptr, data_size_in_bytes, PROT_READ | PROT_WRITE, map_flags, 0, 0, String::formatted("GraphicsBitmap [{}]", size).characters());
 #else
     void* data = mmap(nullptr, data_size_in_bytes, PROT_READ | PROT_WRITE, map_flags, 0, 0);