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https://github.com/RGBCube/serenity
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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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@ -116,7 +116,7 @@ ErrorOr<void> KCOVDevice::ioctl(OpenFileDescription&, unsigned request, Userspac
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}
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}
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ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> KCOVDevice::vmobject_for_mmap(Process& process, Memory::VirtualRange const&, u64&, bool)
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{
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auto pid = process.pid();
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auto maybe_kcov_instance = proc_instance->get(pid);
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@ -126,7 +126,7 @@ ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace
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if (!kcov_instance->vmobject())
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return ENOBUFS; // mmaped, before KCOV_SETBUFSIZE
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return address_space.allocate_region_with_vmobject(range, *kcov_instance->vmobject(), offset, {}, prot, shared);
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return *kcov_instance->vmobject();
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}
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}
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@ -22,7 +22,7 @@ public:
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static void free_process();
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// ^File
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ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
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ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
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ErrorOr<NonnullLockRefPtr<OpenFileDescription>> open(int options) override;
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protected:
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@ -42,7 +42,7 @@ ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKerne
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return length;
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}
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ErrorOr<Memory::Region*> MemoryDevice::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>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
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{
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auto viewed_address = PhysicalAddress(offset);
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@ -61,15 +61,8 @@ ErrorOr<Memory::Region*> MemoryDevice::mmap(Process&, Memory::AddressSpace& addr
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return EINVAL;
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}
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auto vmobject = TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
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return address_space.allocate_region_with_vmobject(
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range,
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move(vmobject),
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0,
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"Mapped Physical Memory"sv,
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prot,
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shared);
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offset = 0;
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return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
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}
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}
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@ -19,7 +19,7 @@ public:
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static NonnullLockRefPtr<MemoryDevice> must_create();
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~MemoryDevice();
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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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MemoryDevice();
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