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[kernel] Allow unmapping non-fully-mapped areas

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The buffer cache will try to clean up a returned buffer by unmapping it,
but it may have only been committed without ever getting mapped. Allow
for page_out to handle non-fully mapped regions.
This commit is contained in:
Justin C. Miller
2020-09-06 16:28:04 -07:00
parent 53a4682418
commit 53d260cc6e
1 changed files with 52 additions and 19 deletions
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71
src/kernel/page_manager.cpp
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@@ -395,42 +395,75 @@ page_manager::page_out(page_table *pml4, uintptr_t virt_addr, size_t count, bool
page_table_indices idx{virt_addr};
page_table *tables[4] = {pml4, nullptr, nullptr, nullptr};
bool found = false;
uintptr_t free_start = 0;
unsigned free_count = 0;
for (; idx[0] < table_entries; idx[0] += 1) {
tables[1] = tables[0]->get(idx[0]);
page_table *table = tables[0]->get(idx[0]);
if (!table) {
constexpr size_t skip = 512 * 512 * 512;
if (count > skip) {
count -= skip;
continue;
}
goto page_out_end;
}
tables[1] = table;
for (; idx[1] < table_entries; idx[1] += 1) {
tables[2] = tables[1]->get(idx[1]);
page_table *table = tables[1]->get(idx[1]);
if (!table) {
constexpr size_t skip = 512 * 512;
if (count > skip) {
count -= skip;
continue;
}
goto page_out_end;
}
tables[2] = table;
for (; idx[2] < table_entries; idx[2] += 1) {
tables[3] = tables[2]->get(idx[2]);
page_table *table = tables[2]->get(idx[2]);
if (!table) {
constexpr size_t skip = 512;
if (count > skip) {
count -= skip;
continue;
}
goto page_out_end;
}
tables[3] = table;
for (; idx[3] < table_entries; idx[3] += 1) {
uintptr_t entry = tables[3]->entries[idx[3]] & ~0xfffull;
if (!found || entry != free_start + free_count * frame_size) {
if (found && free) m_frames.free(free_start, free_count);
free_start = tables[3]->entries[idx[3]] & ~0xfffull;
free_count = 1;
found = true;
} else {
free_count++;
uintptr_t entry = tables[3]->entries[idx[3]];
bool present = entry & 1;
if (present) {
entry &= ~0xfffull;
if (!free_count || entry != free_start + free_count * frame_size) {
if (free_count && free) m_frames.free(free_start, free_count);
free_start = tables[3]->entries[idx[3]] & ~0xfffull;
free_count = 1;
} else {
free_count++;
}
tables[3]->entries[idx[3]] = 0;
}
tables[3]->entries[idx[3]] = 0;
if (--count == 0) {
if (free) m_frames.free(free_start, free_count);
return;
}
if (--count == 0)
goto page_out_end;
}
}
}
}
kassert(0, "Ran to end of page_out");
page_out_end:
if (free && free_count)
m_frames.free(free_start, free_count);
}
void