fix(avapager): Fix evict_page bug with low cache capacities

Author: TalonFloof

src/avapager.c

@@ -63,8 +63,6 @@ void ava_pager_deinit(AvaPager* pager) {
 static AvaPagerSlot* find_slot(AvaPager* pager, ava_pgid_t pgid) {
     uint32_t index = hash_pgid(pgid) % pager->hash_map_size;
     /* TODO: Improve worse-case, currently O(n) due to linear probing */
-    if (!pager->hash_map[index])
-        return NULL;
     for (uint32_t i=0; i < pager->hash_map_size; i++) {
         uint32_t cur = (index + i) % pager->hash_map_size;
         if (pager->hash_map[cur] && pager->hash_map[cur]->pgid == pgid) {
@@ -161,10 +159,11 @@ bool ava_pager_allocate(AvaPager* pager, ava_pgid_t* new_pgid) {
             ava_pager_unpin(pager, 0);
             return false;
         }
-        header->free_page_start = page->header.free.next_free;
         ava_pager_mark_dirty(pager,index);
-        page->header.free.next_free = 0;
         ava_pager_mark_dirty(pager,0);
+
+        header->free_page_start = page->header.free.next_free;
+        page->header.free.next_free = 0;
         *new_pgid = index;
         ava_pager_unpin(pager, index);
         ava_pager_unpin(pager, 0);

src/avatree.c

@@ -13,6 +13,7 @@ static ava_pgid_t create_overflow_chain(AvaPager* pager, char* data, uint32_t si
         ava_pgid_t new_page;
         ava_pager_allocate(pager, &new_page);
         AvaTreePageHeader* page = ava_pager_get(pager, new_page);
+        ava_pager_mark_dirty(pager, new_page);
         page->type = AVA_PAGE_TYPE_OVERFLOW;
 
         if (first_page == 0)
@@ -30,7 +31,6 @@ static ava_pgid_t create_overflow_chain(AvaPager* pager, char* data, uint32_t si
         uint32_t to_write = (size-written > pager->page_size - sizeof(AvaTreePageHeader)) ? (pager->page_size - sizeof(AvaTreePageHeader)) : (size-written);
 
         memcpy((uint8_t*)page + sizeof(AvaTreePageHeader), data + written, to_write);
-        ava_pager_mark_dirty(pager, current_page);
         written += to_write;
         ava_pager_unpin(pager, new_page);
     }

tests/test_avatree.cpp

@@ -63,7 +63,9 @@ class AvaTreeTest : public ::testing::Test {
 
         p_interface = &mock_interface;
         p_file = (AvaFile*)&mock_file;
-        
+
+        /* Test with a low cache capacity to ensure that we don't have page leaks */
+        pager.cache_capacity = 16;
         ava_pager_init(&pager, &p_interface, &p_file);
     }
 
@@ -256,7 +258,7 @@ TEST_F(AvaTreeTest, InsertOverflowTest) {
 
     while (page_id != 0) {
         AvaTreePageHeader* ovf = (AvaTreePageHeader*)ava_pager_get(&pager, page_id);
-        EXPECT_EQ(ovf->type,AVA_PAGE_TYPE_OVERFLOW) << "Page #" << page_id << "was not set as type AVA_PAGE_TYPE_OVERFLOW!";
+        EXPECT_EQ(ovf->type,AVA_PAGE_TYPE_OVERFLOW) << "Page #" << page_id << " was not set as type AVA_PAGE_TYPE_OVERFLOW!";
         size_t header_sz = sizeof(AvaTreePageHeader);
         size_t cap = pager.page_size - header_sz;
         size_t remaining = large_size - read_back.size();