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Kernel: Use RefPtr instead of LockRefPtr for Custody

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By protecting all the RefPtr<Custody> objects that may be accessed from
multiple threads at the same time (with spinlocks), we remove the need
for using LockRefPtr<Custody> (which is basically a RefPtr with a
built-in spinlock.)
This commit is contained in:
Andreas Kling 2022-08-21 01:04:35 +02:00
parent 5331d243c6
commit 728c3fbd14
23 changed files with 143 additions and 102 deletions
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71
Kernel/FileSystem/VirtualFileSystem.cpp
View file

@ -6,6 +6,7 @@
#include <AK/AnyOf.h>
#include <AK/GenericLexer.h>
#include <AK/RefPtr.h>
#include <AK/Singleton.h>
#include <AK/StringBuilder.h>
#include <Kernel/API/POSIX/errno.h>
@ -38,6 +39,7 @@ VirtualFileSystem& VirtualFileSystem::the()
}
UNMAP_AFTER_INIT VirtualFileSystem::VirtualFileSystem()
: m_root_custody(LockRank::None)
{
}
@ -52,14 +54,15 @@ InodeIdentifier VirtualFileSystem::root_inode_id() const
bool VirtualFileSystem::mount_point_exists_at_inode(InodeIdentifier inode_identifier)
{
return m_mounts.with([&](auto& mounts) -> bool {
return any_of(mounts, [&inode_identifier](Mount const& existing_mount) {
return existing_mount.host() && existing_mount.host()->identifier() == inode_identifier;
return any_of(mounts, [&inode_identifier](auto const& existing_mount) {
return existing_mount->host() && existing_mount->host()->identifier() == inode_identifier;
});
});
}
ErrorOr<void> VirtualFileSystem::mount(FileSystem& fs, Custody& mount_point, int flags)
{
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(fs, &mount_point, flags)));
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
auto& inode = mount_point.inode();
dbgln("VirtualFileSystem: Mounting {} at inode {} with flags {}",
@ -70,14 +73,14 @@ ErrorOr<void> VirtualFileSystem::mount(FileSystem& fs, Custody& mount_point, int
dbgln("VirtualFileSystem: Mounting unsuccessful - inode {} is already a mount-point.", inode.identifier());
return EBUSY;
}
Mount mount { fs, &mount_point, flags };
mounts.append(move(mount));
mounts.append(move(new_mount));
return {};
});
}
ErrorOr<void> VirtualFileSystem::bind_mount(Custody& source, Custody& mount_point, int flags)
{
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(source.inode(), mount_point, flags)));
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
auto& inode = mount_point.inode();
dbgln("VirtualFileSystem: Bind-mounting inode {} at inode {}", source.inode().identifier(), inode.identifier());
@ -86,8 +89,7 @@ ErrorOr<void> VirtualFileSystem::bind_mount(Custody& source, Custody& mount_poin
mount_point.inode().identifier());
return EBUSY;
}
Mount mount { source.inode(), mount_point, flags };
mounts.append(move(mount));
mounts.append(move(new_mount));
return {};
});
}
@ -111,11 +113,11 @@ ErrorOr<void> VirtualFileSystem::unmount(Inode& guest_inode)
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
for (size_t i = 0; i < mounts.size(); ++i) {
auto& mount = mounts[i];
if (&mount.guest() != &guest_inode)
if (&mount->guest() != &guest_inode)
continue;
TRY(mount.guest_fs().prepare_to_unmount());
dbgln("VirtualFileSystem: Unmounting file system {}...", mount.guest_fs().fsid());
mounts.unstable_take(i);
TRY(mount->guest_fs().prepare_to_unmount());
dbgln("VirtualFileSystem: Unmounting file system {}...", mount->guest_fs().fsid());
(void)mounts.unstable_take(i);
return {};
}
dbgln("VirtualFileSystem: Nothing mounted on inode {}", guest_inode.identifier());
@ -130,7 +132,7 @@ ErrorOr<void> VirtualFileSystem::mount_root(FileSystem& fs)
return EEXIST;
}
Mount mount { fs, nullptr, root_mount_flags };
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(fs, nullptr, root_mount_flags)));
auto& root_inode = fs.root_inode();
if (!root_inode.is_directory()) {
@ -143,10 +145,13 @@ ErrorOr<void> VirtualFileSystem::mount_root(FileSystem& fs)
dmesgln("VirtualFileSystem: mounted root from {} ({})", fs.class_name(), pseudo_path);
m_mounts.with([&](auto& mounts) {
mounts.append(move(mount));
mounts.append(move(new_mount));
});
m_root_custody = TRY(Custody::try_create(nullptr, ""sv, *m_root_inode, root_mount_flags));
RefPtr<Custody> new_root_custody = TRY(Custody::try_create(nullptr, ""sv, *m_root_inode, root_mount_flags));
m_root_custody.with([&](auto& root_custody) {
swap(root_custody, new_root_custody);
});
return {};
}
@ -154,8 +159,8 @@ auto VirtualFileSystem::find_mount_for_host(InodeIdentifier id) -> Mount*
{
return m_mounts.with([&](auto& mounts) -> Mount* {
for (auto& mount : mounts) {
if (mount.host() && mount.host()->identifier() == id)
return &mount;
if (mount->host() && mount->host()->identifier() == id)
return mount.ptr();
}
return nullptr;
});
@ -165,8 +170,8 @@ auto VirtualFileSystem::find_mount_for_guest(InodeIdentifier id) -> Mount*
{
return m_mounts.with([&](auto& mounts) -> Mount* {
for (auto& mount : mounts) {
if (mount.guest().identifier() == id)
return &mount;
if (mount->guest().identifier() == id)
return mount.ptr();
}
return nullptr;
});
@ -244,7 +249,7 @@ ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::open(StringVi
if ((options & O_CREAT) && (options & O_DIRECTORY))
return EINVAL;
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto custody_or_error = resolve_path(path, base, &parent_custody, options);
if (custody_or_error.is_error()) {
// NOTE: ENOENT with a non-null parent custody signals us that the immediate parent
@ -332,7 +337,7 @@ ErrorOr<void> VirtualFileSystem::mknod(StringView path, mode_t mode, dev_t dev,
if (!is_regular_file(mode) && !is_block_device(mode) && !is_character_device(mode) && !is_fifo(mode) && !is_socket(mode))
return EINVAL;
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto existing_file_or_error = resolve_path(path, base, &parent_custody);
if (!existing_file_or_error.is_error())
return EEXIST;
@ -397,7 +402,7 @@ ErrorOr<void> VirtualFileSystem::mkdir(StringView path, mode_t mode, Custody& ba
path = "/"sv;
}
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
// FIXME: The errors returned by resolve_path_without_veil can leak information about paths that are not unveiled,
// e.g. when the error is EACCESS or similar.
auto result = resolve_path_without_veil(path, base, &parent_custody);
@ -446,7 +451,7 @@ ErrorOr<void> VirtualFileSystem::access(StringView path, int mode, Custody& base
return {};
}
ErrorOr<NonnullLockRefPtr<Custody>> VirtualFileSystem::open_directory(StringView path, Custody& base)
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::open_directory(StringView path, Custody& base)
{
auto custody = TRY(resolve_path(path, base));
auto& inode = custody->inode();
@ -480,11 +485,11 @@ ErrorOr<void> VirtualFileSystem::chmod(StringView path, mode_t mode, Custody& ba
ErrorOr<void> VirtualFileSystem::rename(StringView old_path, StringView new_path, Custody& base)
{
LockRefPtr<Custody> old_parent_custody;
RefPtr<Custody> old_parent_custody;
auto old_custody = TRY(resolve_path(old_path, base, &old_parent_custody, O_NOFOLLOW_NOERROR));
auto& old_inode = old_custody->inode();
LockRefPtr<Custody> new_parent_custody;
RefPtr<Custody> new_parent_custody;
auto new_custody_or_error = resolve_path(new_path, base, &new_parent_custody);
if (new_custody_or_error.is_error()) {
if (new_custody_or_error.error().code() != ENOENT || !new_parent_custody)
@ -630,7 +635,7 @@ ErrorOr<void> VirtualFileSystem::link(StringView old_path, StringView new_path,
auto old_custody = TRY(resolve_path(old_path, base));
auto& old_inode = old_custody->inode();
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto new_custody_or_error = resolve_path(new_path, base, &parent_custody);
if (!new_custody_or_error.is_error())
return EEXIST;
@ -660,7 +665,7 @@ ErrorOr<void> VirtualFileSystem::link(StringView old_path, StringView new_path,
ErrorOr<void> VirtualFileSystem::unlink(StringView path, Custody& base)
{
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto custody = TRY(resolve_path(path, base, &parent_custody, O_NOFOLLOW_NOERROR | O_UNLINK_INTERNAL));
auto& inode = custody->inode();
@ -690,7 +695,7 @@ ErrorOr<void> VirtualFileSystem::unlink(StringView path, Custody& base)
ErrorOr<void> VirtualFileSystem::symlink(StringView target, StringView linkpath, Custody& base)
{
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto existing_custody_or_error = resolve_path(linkpath, base, &parent_custody);
if (!existing_custody_or_error.is_error())
return EEXIST;
@ -719,7 +724,7 @@ ErrorOr<void> VirtualFileSystem::symlink(StringView target, StringView linkpath,
ErrorOr<void> VirtualFileSystem::rmdir(StringView path, Custody& base)
{
LockRefPtr<Custody> parent_custody;
RefPtr<Custody> parent_custody;
auto custody = TRY(resolve_path(path, base, &parent_custody));
auto& inode = custody->inode();
@ -766,7 +771,7 @@ ErrorOr<void> VirtualFileSystem::for_each_mount(Function<ErrorOr<void>(Mount con
{
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
for (auto& mount : mounts)
TRY(callback(mount));
TRY(callback(*mount));
return {};
});
}
@ -776,9 +781,9 @@ void VirtualFileSystem::sync()
FileSystem::sync();
}
Custody& VirtualFileSystem::root_custody()
NonnullRefPtr<Custody> VirtualFileSystem::root_custody()
{
return *m_root_custody;
return m_root_custody.with([](auto& root_custody) -> NonnullRefPtr<Custody> { return *root_custody; });
}
UnveilNode const& VirtualFileSystem::find_matching_unveiled_path(StringView path)
@ -871,7 +876,7 @@ ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView p
return {};
}
ErrorOr<NonnullLockRefPtr<Custody>> VirtualFileSystem::resolve_path(StringView path, Custody& base, LockRefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path(StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
// FIXME: The errors returned by resolve_path_without_veil can leak information about paths that are not unveiled,
// e.g. when the error is EACCESS or similar.
@ -899,7 +904,7 @@ static bool safe_to_follow_symlink(Inode const& inode, InodeMetadata const& pare
return false;
}
ErrorOr<NonnullLockRefPtr<Custody>> VirtualFileSystem::resolve_path_without_veil(StringView path, Custody& base, LockRefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path_without_veil(StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
if (symlink_recursion_level >= symlink_recursion_limit)
return ELOOP;
@ -910,7 +915,7 @@ ErrorOr<NonnullLockRefPtr<Custody>> VirtualFileSystem::resolve_path_without_veil
GenericLexer path_lexer(path);
auto& current_process = Process::current();
NonnullLockRefPtr<Custody> custody = path[0] == '/' ? root_custody() : base;
NonnullRefPtr<Custody> custody = path[0] == '/' ? root_custody() : base;
bool extra_iteration = path[path.length() - 1] == '/';
while (!path_lexer.is_eof() || extra_iteration) {