forked from Bananymous/banan-os
Kernel: Implement MAP_SHARED for regular files
Every inode holds a weak pointer to shared file data. This contains physical addresses of pages for inode file data. Physical addresses are allocated and read on demand. When last shared mapping is unmapped. The inodes shared data is freed and written to the inode.
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9fc75fe445
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@ -3,6 +3,7 @@
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#include <BAN/RefPtr.h>
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#include <BAN/String.h>
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#include <BAN/StringView.h>
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#include <BAN/WeakPtr.h>
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#include <BAN/Vector.h>
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#include <kernel/API/DirectoryEntry.h>
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@ -17,6 +18,9 @@ namespace Kernel
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using namespace API;
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class FileBackedRegion;
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class SharedFileData;
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class Inode : public BAN::RefCounted<Inode>
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{
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public:
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@ -112,6 +116,9 @@ namespace Kernel
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private:
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mutable RecursiveSpinLock m_lock;
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BAN::WeakPtr<SharedFileData> m_shared_region;
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friend class FileBackedRegion;
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};
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}
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@ -6,6 +6,17 @@
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namespace Kernel
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{
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struct SharedFileData : public BAN::RefCounted<SharedFileData>, public BAN::Weakable<SharedFileData>
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{
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~SharedFileData();
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// FIXME: this should probably be ordered tree like map
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// for fast lookup and less memory usage
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BAN::Vector<paddr_t> pages;
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BAN::RefPtr<Inode> inode;
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uint8_t page_buffer[PAGE_SIZE];
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};
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class FileBackedRegion final : public MemoryRegion
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{
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BAN_NON_COPYABLE(FileBackedRegion);
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@ -25,6 +36,8 @@ namespace Kernel
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private:
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BAN::RefPtr<Inode> m_inode;
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const off_t m_offset;
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BAN::RefPtr<SharedFileData> m_shared_data;
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};
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}
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@ -9,9 +9,6 @@ namespace Kernel
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{
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ASSERT(inode->mode().ifreg());
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if (type != Type::PRIVATE)
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return BAN::Error::from_errno(ENOTSUP);
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if (offset < 0 || offset % PAGE_SIZE || size == 0)
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return BAN::Error::from_errno(EINVAL);
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if (size > (size_t)inode->size() || (size_t)offset > (size_t)inode->size() - size)
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@ -24,6 +21,21 @@ namespace Kernel
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TRY(region->initialize(address_range));
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if (type == Type::SHARED)
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{
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LockGuard _(inode->m_lock);
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if (inode->m_shared_region.valid())
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region->m_shared_data = inode->m_shared_region.lock();
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else
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{
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auto shared_data = TRY(BAN::RefPtr<SharedFileData>::create());
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TRY(shared_data->pages.resize(BAN::Math::div_round_up<size_t>(inode->size(), PAGE_SIZE)));
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shared_data->inode = inode;
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inode->m_shared_region = TRY(shared_data->get_weak_ptr());
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region->m_shared_data = BAN::move(shared_data);
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}
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}
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return region;
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}
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@ -39,7 +51,8 @@ namespace Kernel
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if (m_vaddr == 0)
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return;
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ASSERT(m_type == Type::PRIVATE);
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if (m_type == Type::SHARED)
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return;
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size_t needed_pages = BAN::Math::div_round_up<size_t>(m_size, PAGE_SIZE);
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for (size_t i = 0; i < needed_pages; i++)
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@ -50,10 +63,30 @@ namespace Kernel
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}
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}
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SharedFileData::~SharedFileData()
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{
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for (size_t i = 0; i < pages.size(); i++)
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{
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if (pages[i] == 0)
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continue;
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{
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auto& page_table = PageTable::current();
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LockGuard _(page_table);
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(pages[i], 0, PageTable::Flags::Present);
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memcpy(page_buffer, (void*)0, PAGE_SIZE);
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page_table.unmap_page(0);
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}
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if (auto ret = inode->write(i * PAGE_SIZE, page_buffer, PAGE_SIZE); ret.is_error())
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dwarnln("{}", ret.error());
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}
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}
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BAN::ErrorOr<bool> FileBackedRegion::allocate_page_containing(vaddr_t address)
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{
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ASSERT(m_type == Type::PRIVATE);
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ASSERT(contains(address));
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// Check if address is already mapped
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@ -61,44 +94,89 @@ namespace Kernel
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if (m_page_table.physical_address_of(vaddr) != 0)
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return false;
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// Map new physcial page to address
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paddr_t paddr = Heap::get().take_free_page();
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if (paddr == 0)
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return BAN::Error::from_errno(ENOMEM);
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m_page_table.map_page_at(paddr, vaddr, m_flags);
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if (m_type == Type::PRIVATE)
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{
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// Map new physcial page to address
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paddr_t paddr = Heap::get().take_free_page();
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if (paddr == 0)
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return BAN::Error::from_errno(ENOMEM);
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m_page_table.map_page_at(paddr, vaddr, m_flags);
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size_t file_offset = m_offset + (vaddr - m_vaddr);
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size_t bytes = BAN::Math::min<size_t>(m_size - file_offset, PAGE_SIZE);
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size_t file_offset = m_offset + (vaddr - m_vaddr);
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size_t bytes = BAN::Math::min<size_t>(m_size - file_offset, PAGE_SIZE);
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BAN::ErrorOr<size_t> read_ret = 0;
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BAN::ErrorOr<size_t> read_ret = 0;
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// Zero out the new page
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if (&PageTable::current() == &m_page_table)
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read_ret = m_inode->read(file_offset, (void*)vaddr, bytes);
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// Zero out the new page
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if (&PageTable::current() == &m_page_table)
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read_ret = m_inode->read(file_offset, (void*)vaddr, bytes);
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else
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{
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auto& page_table = PageTable::current();
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LockGuard _(page_table);
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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read_ret = m_inode->read(file_offset, (void*)0, bytes);
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memset((void*)0, 0x00, PAGE_SIZE);
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page_table.unmap_page(0);
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}
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if (read_ret.is_error())
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{
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Heap::get().release_page(paddr);
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m_page_table.unmap_page(vaddr);
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return read_ret.release_error();
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}
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if (read_ret.value() < bytes)
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{
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dwarnln("Only {}/{} bytes read", read_ret.value(), bytes);
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Heap::get().release_page(paddr);
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m_page_table.unmap_page(vaddr);
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return BAN::Error::from_errno(EIO);
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}
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}
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else if (m_type == Type::SHARED)
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{
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LockGuard _(m_inode->m_lock);
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ASSERT(m_inode->m_shared_region.valid());
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ASSERT(m_shared_data->pages.size() == BAN::Math::div_round_up<size_t>(m_inode->size(), PAGE_SIZE));
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auto& pages = m_shared_data->pages;
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size_t page_index = (vaddr - m_vaddr) / PAGE_SIZE;
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if (pages[page_index] == 0)
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{
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pages[page_index] = Heap::get().take_free_page();
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if (pages[page_index] == 0)
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return BAN::Error::from_errno(ENOMEM);
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size_t offset = vaddr - m_vaddr;
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size_t bytes = BAN::Math::min<size_t>(m_size - offset, PAGE_SIZE);
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TRY(m_inode->read(offset, m_shared_data->page_buffer, bytes));
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auto& page_table = PageTable::current();
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// TODO: check if this can cause deadlock?
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LockGuard page_table_lock(page_table);
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ASSERT(page_table.is_page_free(0));
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page_table.map_page_at(pages[page_index], 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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memcpy((void*)0, m_shared_data->page_buffer, PAGE_SIZE);
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page_table.unmap_page(0);
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}
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paddr_t paddr = pages[page_index];
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ASSERT(paddr);
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m_page_table.map_page_at(paddr, vaddr, m_flags);
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}
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else
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{
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LockGuard _(PageTable::current());
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ASSERT(PageTable::current().is_page_free(0));
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PageTable::current().map_page_at(paddr, 0, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
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read_ret = m_inode->read(file_offset, (void*)0, bytes);
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memset((void*)0, 0x00, PAGE_SIZE);
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PageTable::current().unmap_page(0);
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}
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if (read_ret.is_error())
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{
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Heap::get().release_page(paddr);
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m_page_table.unmap_page(vaddr);
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return read_ret.release_error();
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}
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if (read_ret.value() < bytes)
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{
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dwarnln("Only {}/{} bytes read", read_ret.value(), bytes);
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Heap::get().release_page(paddr);
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m_page_table.unmap_page(vaddr);
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return BAN::Error::from_errno(EIO);
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ASSERT_NOT_REACHED();
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}
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return true;
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@ -863,7 +863,7 @@ namespace Kernel
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if (!(inode_flags & O_RDONLY))
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return BAN::Error::from_errno(EACCES);
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if (region_type == MemoryRegion::Type::SHARED)
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if (!(args->prot & PROT_WRITE) || !(inode_flags & O_WRONLY))
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if ((args->prot & PROT_WRITE) && !(inode_flags & O_WRONLY))
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return BAN::Error::from_errno(EACCES);
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auto region = TRY(FileBackedRegion::create(
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