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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/FileSystem/InodeFile.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -85,16 +85,11 @@ ErrorOr<void> InodeFile::ioctl(OpenFileDescription& description, unsigned reques
}
}
ErrorOr<Memory::Region*> InodeFile::mmap(Process&, Memory::AddressSpace& address_space, OpenFileDescription& description, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> InodeFile::vmobject_for_mmap(Process&, Memory::VirtualRange const&, u64&, bool shared)
{
// FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
LockRefPtr<Memory::InodeVMObject> vmobject;
if (shared)
vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
else
vmobject = TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
auto path = TRY(description.pseudo_path());
return address_space.allocate_region_with_vmobject(range, vmobject.release_nonnull(), offset, path->view(), prot, shared);
return TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode()));
return TRY(Memory::PrivateInodeVMObject::try_create_with_inode(inode()));
}
ErrorOr<NonnullOwnPtr<KString>> InodeFile::pseudo_path(OpenFileDescription const&) const