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Kernel: Simplify the File memory-mapping API

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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.
This commit is contained in:
Andreas Kling 2022-08-23 18:51:18 +02:00
parent cf16b2c8e6
commit 30861daa93
15 changed files with 49 additions and 58 deletions
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4
Kernel/Devices/KCOVDevice.cpp
View file

@ -116,7 +116,7 @@ ErrorOr<void> KCOVDevice::ioctl(OpenFileDescription&, unsigned request, Userspac
}
}
ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> KCOVDevice::vmobject_for_mmap(Process& process, Memory::VirtualRange const&, u64&, bool)
{
auto pid = process.pid();
auto maybe_kcov_instance = proc_instance->get(pid);
@ -126,7 +126,7 @@ ErrorOr<Memory::Region*> KCOVDevice::mmap(Process& process, Memory::AddressSpace
if (!kcov_instance->vmobject())
return ENOBUFS; // mmaped, before KCOV_SETBUFSIZE
return address_space.allocate_region_with_vmobject(range, *kcov_instance->vmobject(), offset, {}, prot, shared);
return *kcov_instance->vmobject();
}
}

2
Kernel/Devices/KCOVDevice.h
View file

@ -22,7 +22,7 @@ public:
static void free_process();
// ^File
ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> open(int options) override;
protected:

13
Kernel/Devices/MemoryDevice.cpp
View file

@ -42,7 +42,7 @@ ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKerne
return length;
}
ErrorOr<Memory::Region*> MemoryDevice::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
{
auto viewed_address = PhysicalAddress(offset);
@ -61,15 +61,8 @@ ErrorOr<Memory::Region*> MemoryDevice::mmap(Process&, Memory::AddressSpace& addr
return EINVAL;
}
auto vmobject = TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
return address_space.allocate_region_with_vmobject(
range,
move(vmobject),
0,
"Mapped Physical Memory"sv,
prot,
shared);
offset = 0;
return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
}
}

2
Kernel/Devices/MemoryDevice.h
View file

@ -19,7 +19,7 @@ public:
static NonnullLockRefPtr<MemoryDevice> must_create();
~MemoryDevice();
virtual ErrorOr<Memory::Region*> mmap(Process&, Memory::AddressSpace&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
virtual ErrorOr<NonnullLockRefPtr<Memory::VMObject>> vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64& offset, bool shared) override;
private:
MemoryDevice();