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page cache: zero upper bytes on unaligned truncate

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Matheus
2026-08-20 23:55:09 -03:00
parent 40975dfcb2
commit ced642b70c
1 changed files with 23 additions and 4 deletions
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kernel-src/mm/cache.c
+23 -4
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@@ -2,6 +2,7 @@
#include <semaphore.h>
#include <logging.h>
#include <kernel/init.h>
#include <string.h>
typedef struct {
list_node_t list_node;
@@ -228,10 +229,7 @@ void mm_cache_take_page(page_t *page) {
page_notify_waiters(page);
}
static void truncate_iterate(void *p) {
page_t *page = p;
__atomic_sub_fetch(&mm_cache_cached_pages, 1, __ATOMIC_RELAXED);
static void truncate_page(page_t *page) {
int old_flags = __atomic_load_n(&page->flags, __ATOMIC_RELAXED);
for (;;) {
int new_flags = (old_flags | PAGE_FLAGS_TRUNCATED) & ~PAGE_FLAGS_PINNED;
@@ -248,11 +246,32 @@ static void truncate_iterate(void *p) {
mm_release_page(mm_get_page_address(page));
}
static void truncate_iterate(void *p) {
__atomic_sub_fetch(&mm_cache_cached_pages, 1, __ATOMIC_RELAXED);
truncate_page(p);
}
int mm_cache_truncate(vnode_t *vnode, uintmax_t offset) {
uintmax_t min_page = ROUND_UP(offset, PAGE_SIZE) / PAGE_SIZE;
size_t page_offset = offset % PAGE_SIZE;
pushlock_acquire_exclusive(&vnode->pages_lock);
if (page_offset) {
uintmax_t page_start = offset - page_offset;
page_t *page = lookup_page(vnode, page_start);
if (page) {
int flags = __atomic_load_n(&page->flags, __ATOMIC_ACQUIRE);
if (flags & PAGE_FLAGS_READY) {
void *address = MAKE_HHDM(mm_get_page_address(page));
memset((char *)address + page_offset, 0, PAGE_SIZE - page_offset);
} else {
remove_page(vnode, page_start);
truncate_page(page);
}
}
}
trie_iterate(&vnode->pages, min_page, UINT64_MAX, truncate_iterate);
trie_truncate(&vnode->pages, min_page);