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Kernel: Don't fail on unlocking nonexistent file locks

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I haven't found any POSIX specification on this, but the Linux kernel
appears to handle it like that.

This is required by QEMU, as it just bulk-unlocks all its file locking
bytes without checking first if they are held.
This commit is contained in:
Tim Schumacher 2022-05-13 12:20:57 +02:00 committed by Brian Gianforcaro
parent 7d3f71a648
commit dc6016cd18
Notes: sideshowbarker 2024-07-17 09:39:38 +09:00 
Author: https://github.com/timschumi
Commit: https://github.com/SerenityOS/serenity/commit/dc6016cd18
Pull-request: https://github.com/SerenityOS/serenity/pull/13971
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/bgianfo ✅
Reviewed-by: https://github.com/kleinesfilmroellchen
Reviewed-by: https://github.com/linusg
1 changed files with 7 additions and 10 deletions
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17
Kernel/FileSystem/Inode.cpp
View file

@ -291,18 +291,14 @@ static inline ErrorOr<void> normalize_flock(OpenFileDescription const& descripti
return {};
}
ErrorOr<void> Inode::can_apply_flock(OpenFileDescription const& description, flock const& new_lock) const
ErrorOr<void> Inode::can_apply_flock(OpenFileDescription const&, flock const& new_lock) const
{
VERIFY(new_lock.l_whence == SEEK_SET);
if (new_lock.l_type == F_UNLCK)
return {};
return m_flocks.with([&](auto& flocks) -> ErrorOr<void> {
if (new_lock.l_type == F_UNLCK) {
for (auto const& lock : flocks) {
if (&description == lock.owner && lock.start == new_lock.l_start && lock.len == new_lock.l_len)
return {};
}
return EINVAL;
}
for (auto const& lock : flocks) {
if (!range_overlap(lock.start, lock.len, new_lock.l_start, new_lock.l_len))
continue;
@ -329,10 +325,11 @@ ErrorOr<void> Inode::apply_flock(Process const& process, OpenFileDescription con
for (size_t i = 0; i < flocks.size(); ++i) {
if (&description == flocks[i].owner && flocks[i].start == new_lock.l_start && flocks[i].len == new_lock.l_len) {
flocks.remove(i);
return {};
}
}
return EINVAL;
// Judging by the Linux implementation, unlocking a non-existent lock also works.
return {};
}
TRY(flocks.try_append(Flock { new_lock.l_start, new_lock.l_len, &description, process.pid().value(), new_lock.l_type }));