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1dfc9e2df3
Immutable mounts are mounts that can't be changed in any aspect, if the VFSRootContext that hold them is used by a process. This includes two operations on a mount: 1. Trying to remove the mount from the mount table. 2. Trying to change the flags of the mount. The condition of a VFSRootContext being held by a process or not is crucial, as the intention is to allow removal of mounts that marked as immutable if the VFSRootContext is not being used anymore (for example, if the container that was created with such context stopped). Marking mounts as immutable on the first VFS root context essentially ensures they will never be modified because there will be a process using that context (which is the "main" VFS root context in the system runtime). It should be noted that setting a mount as immutable can be done in creation time of the mount by passing the MS_IMMUTABLE flag, or by doing a remount with MS_IMMUTABLE flag.
82 lines
1.9 KiB
C++
82 lines
1.9 KiB
C++
/*
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* Copyright (c) 2018-2023, 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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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/FileSystem/FileSystem.h>
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#include <Kernel/FileSystem/Inode.h>
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#include <Kernel/FileSystem/Mount.h>
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namespace Kernel {
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Mount::Mount(NonnullRefPtr<Inode> source, int flags)
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: m_details(Mount::Details(source->fs(), move(source)))
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{
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set_flags(flags);
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}
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Mount::Mount(NonnullRefPtr<Inode> source, NonnullRefPtr<Custody> host_custody, int flags)
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: m_details(Mount::Details(source->fs(), move(source)))
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, m_host_custody(move(host_custody))
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{
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set_flags(flags);
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}
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void Mount::set_flags(int flags)
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{
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// NOTE: We use a spinlock to serialize access, to protect against
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// a case which the user requested to set the immutable flag, and
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// there's another ongoing call to set the flags without it.
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m_flags.with([this, flags](auto& current_flags) {
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if (flags & MS_IMMUTABLE)
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m_immutable.set();
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current_flags = flags;
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if (m_immutable.was_set())
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current_flags |= MS_IMMUTABLE;
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});
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}
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void Mount::delete_mount_from_list(Mount& mount)
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{
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dbgln("VirtualFileSystem: Unmounting file system {}...", mount.guest_fs().fsid());
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VERIFY(mount.m_vfs_list_node.is_in_list());
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mount.m_vfs_list_node.remove();
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delete &mount;
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}
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ErrorOr<NonnullOwnPtr<KString>> Mount::absolute_path() const
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{
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if (!m_host_custody)
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return KString::try_create("/"sv);
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return m_host_custody->try_serialize_absolute_path();
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}
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RefPtr<Inode> Mount::host()
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{
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if (!m_host_custody)
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return nullptr;
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return m_host_custody->inode();
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}
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RefPtr<Inode const> Mount::host() const
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{
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if (!m_host_custody)
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return nullptr;
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return m_host_custody->inode();
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}
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RefPtr<Custody const> Mount::host_custody() const
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{
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return m_host_custody;
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}
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RefPtr<Custody> Mount::host_custody()
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{
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return m_host_custody;
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}
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}
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