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Kernel: Simplify the File memory-mapping API
Before this change, we had File::mmap() which did all the work of setting up a VMObject, and then creating a Region in the current process's address space. This patch simplifies the interface by removing the region part. Files now only have to return a suitable VMObject from vmobject_for_mmap(), and then sys$mmap() itself will take care of actually mapping it into the address space. This fixes an issue where we'd try to block on I/O (for inode metadata lookup) while holding the address space spinlock. It also reduces time spent holding the address space lock.
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parent
cf16b2c8e6
commit
30861daa93
15 changed files with 49 additions and 58 deletions
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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@ -17,12 +17,12 @@ AnonymousFile::AnonymousFile(NonnullLockRefPtr<Memory::AnonymousVMObject> vmobje
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AnonymousFile::~AnonymousFile() = default;
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ErrorOr<Memory::Region*> AnonymousFile::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> AnonymousFile::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool)
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{
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if (offset != 0)
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return EINVAL;
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return address_space.allocate_region_with_vmobject(range, m_vmobject, offset, {}, prot, shared);
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return m_vmobject;
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}
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ErrorOr<NonnullOwnPtr<KString>> AnonymousFile::pseudo_path(OpenFileDescription const&) const
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2021-2022, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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@ -20,7 +20,7 @@ public:
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virtual ~AnonymousFile() override;
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virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
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virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
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private:
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virtual StringView class_name() const override { return "AnonymousFile"sv; }
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@ -35,7 +35,7 @@ ErrorOr<void> File::ioctl(OpenFileDescription&, unsigned, Userspace<void*>)
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return ENOTTY;
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}
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ErrorOr<Memory::Region*> File::mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64, int, bool)
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> File::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool)
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{
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return ENODEV;
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}
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@ -64,11 +64,11 @@ public:
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// - Can be overridden in subclasses to implement arbitrary functionality.
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// - Subclasses should take care to validate incoming addresses before dereferencing.
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//
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// mmap()
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// vmobject_for_mmap()
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//
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// - Optional. If unimplemented, mmap() on this File will fail with -ENODEV.
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// - Called by mmap() when userspace wants to memory-map this File somewhere.
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// - Should create a Region in the Process and return it if successful.
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// - Should return a VMObject suitable for mapping into the calling process.
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class File
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: public AtomicRefCounted<File>
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@ -90,7 +90,7 @@ public:
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virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) = 0;
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virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) = 0;
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virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg);
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virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared);
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virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared);
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virtual ErrorOr<struct stat> stat() const { return EBADF; }
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// Although this might be better described "name" or "description", these terms already have other meanings.
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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@ -85,16 +85,11 @@ ErrorOr<void> InodeFile::ioctl(OpenFileDescription& description, unsigned reques
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}
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}
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ErrorOr<Memory::Region*> InodeFile::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription& description, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> InodeFile::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool shared)
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{
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// FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
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LockRefPtr<Memory::InodeVMObject> vmobject;
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if (shared)
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vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
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else
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vmobject = TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
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auto path = TRY(description.pseudo_path());
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return address_space.allocate_region_with_vmobject(range, vmobject.release_nonnull(), offset, path->view(), prot, shared);
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return TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
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return TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
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}
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ErrorOr<NonnullOwnPtr<KString>> InodeFile::pseudo_path(OpenFileDescription const&) const
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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@ -33,7 +33,7 @@ public:
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virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
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virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override;
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virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override;
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virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
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virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
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virtual ErrorOr<struct stat> stat() const override { return inode().metadata().stat(); }
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virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(OpenFileDescription const&) const override;
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@ -374,9 +374,9 @@ InodeMetadata OpenFileDescription::metadata() const
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return {};
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}
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ErrorOr<Memory::Region*> OpenFileDescription::mmap(Process& process, Memory::AddressSpace& address_space, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> OpenFileDescription::vmobject_for_mmap(Process& process, Memory::VirtualRange const& range, u64& offset, bool shared)
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{
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return m_file->mmap(process, address_space, *this, range, offset, prot, shared);
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return m_file->vmobject_for_mmap(process, range, offset, shared);
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}
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ErrorOr<void> OpenFileDescription::truncate(u64 length)
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@ -92,7 +92,7 @@ public:
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RefPtr<Custody> custody();
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RefPtr<Custody const> custody() const;
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ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, Memory::VirtualRange const&, u64 offset, int prot, bool shared);
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared);
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bool is_blocking() const;
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void set_blocking(bool b);
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