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Kernel: Improve some comments in Space

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Remove bogus FIXME's and improve some comments.
This commit is contained in:
Andreas Kling 2021-07-27 15:04:04 +02:00
parent a085168c52
commit c69e147b8b
1 changed files with 13 additions and 15 deletions
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28
Kernel/VM/Space.cpp
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@ -66,7 +66,7 @@ KResult Space::unmap_mmap_range(VirtualAddress addr, size_t size)
return EPERM;
// Remove the old region from our regions tree, since were going to add another region
// with the exact same start address, but dont deallocate it yet
// with the exact same start address, but don't deallocate it yet.
auto region = take_region(*old_region);
// We manually unmap the old region here, specifying that we *don't* want the VM deallocated.
@ -90,12 +90,11 @@ KResult Space::unmap_mmap_range(VirtualAddress addr, size_t size)
return KSuccess;
}
// Try again while checkin multiple regions at a time
// slow: without caching
const auto& regions = find_regions_intersecting(range_to_unmap);
// Try again while checking multiple regions at a time.
auto const& regions = find_regions_intersecting(range_to_unmap);
// Check if any of the regions is not mmapped, to not accidentally
// error-out with just half a region map left
// Check if any of the regions is not mmap'ed, to not accidentally
// error out with just half a region map left.
for (auto* region : regions) {
if (!region->is_mmap())
return EPERM;
@ -104,20 +103,20 @@ KResult Space::unmap_mmap_range(VirtualAddress addr, size_t size)
Vector<Region*, 2> new_regions;
for (auto* old_region : regions) {
// if it's a full match we can delete the complete old region
// If it's a full match we can remove the entire old region.
if (old_region->range().intersect(range_to_unmap).size() == old_region->size()) {
deallocate_region(*old_region);
continue;
}
// Remove the old region from our regions tree, since were going to add another region
// with the exact same start address, but dont deallocate it yet
// with the exact same start address, but don't deallocate it yet.
auto region = take_region(*old_region);
// We manually unmap the old region here, specifying that we *don't* want the VM deallocated.
region->unmap(Region::ShouldDeallocateVirtualMemoryRange::No);
// Otherwise just split the regions and collect them for future mapping
// Otherwise, split the regions and collect them for future mapping.
auto split_regions_or_error = try_split_region_around_range(*region, range_to_unmap);
if (split_regions_or_error.is_error())
return split_regions_or_error.error();
@ -125,9 +124,11 @@ KResult Space::unmap_mmap_range(VirtualAddress addr, size_t size)
if (new_regions.try_extend(split_regions_or_error.value()))
return ENOMEM;
}
// Instead we give back the unwanted VM manually at the end.
// Give back any unwanted VM to the range allocator.
page_directory().range_allocator().deallocate(range_to_unmap);
// And finally we map the new region(s) using our page directory (they were just allocated and don't have one).
// And finally map the new region(s) into our page directory.
for (auto* new_region : new_regions) {
new_region->map(page_directory());
}
@ -208,10 +209,8 @@ KResultOr<Region*> Space::allocate_region_with_vmobject(Range const& range, Nonn
auto* added_region = add_region(region.release_nonnull());
if (!added_region)
return ENOMEM;
if (!added_region->map(page_directory())) {
// FIXME: What is an appropriate error code here, really?
if (!added_region->map(page_directory()))
return ENOMEM;
}
return added_region;
}
@ -266,7 +265,6 @@ Vector<Region*> Space::find_regions_intersecting(const Range& range)
ScopedSpinLock lock(m_lock);
// FIXME: Maybe take the cache from the single lookup?
auto found_region = m_regions.find_largest_not_above(range.base().get());
if (!found_region)
return regions;