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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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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()));
}
}