ftl: maintain state for the transaction that is currently active

include/ftl.h

@@ -15,11 +15,14 @@ struct ftl_page_desc {
 	uint32_t subtrees[32];
 } __attribute__((packed));
 
+struct ftl_tlb_entry {
+	uint32_t va, page;
+	uint8_t flags;
+};
+
 struct ftl_map {
 	struct flash_dev *dev;
-	unsigned flags;
-	uint32_t last_va;
-	uint32_t last_pa;
+	struct ftl_tlb_entry outstanding;
 	uint32_t offset;
 	uint32_t head, tail;
 	uint32_t root;
@@ -33,9 +36,9 @@ struct ftl_map {
 	uint8_t epoch;
 };
 
-#define FTL_CACHED_VA BIT(0)
-#define FTL_UNMAPPED  BIT(1)
-#define FTL_DIRTY     BIT(2)
+#define FTL_PRESENT    BIT(7)
+#define FTL_NO_MAPPING BIT(6)
+#define FTL_AGE(x)     (x & BITS(0, 3))
 
 #define FTL_MAX_ATTEMPTS 8
 

source/ftl/ftl.c

@@ -56,30 +56,37 @@ static int ftl_seek(struct ftl_map *map, uint32_t va)
 	offset = va & ((1 << map->log2_page_size) - 1);
 	va >>= map->log2_page_size;
 
-	if ((map->flags & FTL_CACHED_VA) && map->last_va != va &&
-		ftl_sync(map) < 0)
-		return -1;
-
-	if ((ret = trace_path(map, NULL, &page, va)) < 0 &&
-		ret != -ERR_NOT_FOUND)
-		return -1;
-
-	if (offset < map->offset)
-		return -1;
+	if (!(map->outstanding.flags & FTL_PRESENT) || map->outstanding.va != va) {
+		if (ftl_sync(map) < 0)
+			return -1;
 
-	if (offset == map->offset)
-		return 0;
+		if ((ret = trace_path(map, NULL, &page, va)) < 0 &&
+			ret != -ERR_NOT_FOUND)
+			return -1;
 
-	if (map->offset == 0) {
 		if (prepare_head(map) < 0)
 			return -1;
 
-		if (ret == -ERR_NOT_FOUND)
+		map->outstanding.flags |= FTL_PRESENT;
+		map->outstanding.va = va;
+		map->outstanding.page = page;
+
+		if (ret == -ERR_NOT_FOUND) {
+			map->outstanding.flags |= FTL_NO_MAPPING;
 			++map->nused_pages;
+		}
+
+		map->offset = 0;
 	}
 
+	if (offset < map->offset)
+		return -1;
+
+	if (offset == map->offset)
+		return 0;
+
 	dst = map->head << map->log2_page_size;
-	src = page << map->log2_page_size;
+	src = map->outstanding.page << map->log2_page_size;
 	len = offset - map->offset;
 
 	if (ret == -ERR_NOT_FOUND)
@@ -107,7 +114,6 @@ size_t ftl_write(struct ftl_map *map, uint32_t va, const void *udata,
 		return 0;
 
 	map->offset += len;
-	map->flags |= FTL_DIRTY;
 
 	return len;
 }
@@ -116,21 +122,16 @@ int ftl_sync(struct ftl_map *map)
 {
 	struct ftl_page_desc page_desc;
 	size_t len;
-	int ret;
-	uint32_t page, dst, src;
+	uint32_t dst, src;
 
-	if (!(map->flags & FTL_DIRTY))
+	if (!(map->outstanding.flags & FTL_PRESENT))
 		return 0;
 
-	if ((ret = trace_path(map, &page_desc, &page, map->last_va)) < 0 &&
-		ret != -ERR_NOT_FOUND)
-		return -1;
-
 	dst = (map->head << map->log2_page_size) + map->offset;
-	src = (page << map->log2_page_size) + map->offset;
+	src = (map->outstanding.page << map->log2_page_size) + map->offset;
 	len = (1 << map->log2_page_size) - map->offset;
 
-	if (map->flags & FTL_UNMAPPED)
+	if (map->outstanding.flags & FTL_NO_MAPPING)
 		flash_write0(map->dev, dst, len);
 	else
 		flash_copy(map->dev, dst, src, len);
@@ -141,7 +142,7 @@ int ftl_sync(struct ftl_map *map)
 		return -1;
 
 	map->offset = 0;
-	map->flags &= ~(FTL_CACHED_VA | FTL_UNMAPPED | FTL_DIRTY);
+	map->outstanding.flags = 0;
 
 	return 0;
 }

source/ftl/map.c

@@ -380,9 +380,8 @@ static void reset_map(struct ftl_map *map)
 
 	map->nblocks = flash_get_size(map->dev) >> map->log2_block_size;
 
-	map->flags = 0;
-	map->last_va = 0;
-	map->last_pa = 0;
+	memset(&map->outstanding, 0, sizeof map->outstanding);
+
 	map->offset = 0;
 	map->head = 0;
 	map->tail = 0;
@@ -459,21 +458,6 @@ int trace_path(struct ftl_map *map, struct ftl_page_desc *new_page_desc,
 	uint8_t depth = 0;
 	uint32_t upage = map->root;
 
-#if 0
-	/* FIXME */
-	if (!new_page_desc && (map->flags & FTL_CACHED_VA) && map->last_va == va) {
-		if (map->flags & FTL_UNMAPPED)
-			return -1;
-
-		if (page)
-			*page = map->last_pa;
-
-		return 0;
-	}
-#endif
-
-	map->flags &= ~(FTL_CACHED_VA | FTL_UNMAPPED);
-
 	if (new_page_desc)
 		new_page_desc->va = va;
 
@@ -509,10 +493,6 @@ int trace_path(struct ftl_map *map, struct ftl_page_desc *new_page_desc,
 	if (page)
 		*page = upage;
 
-	map->flags |= FTL_CACHED_VA;
-	map->last_va = va;
-	map->last_pa = upage;
-
 	return 0;
 
 err_not_found:
@@ -522,8 +502,5 @@ err_not_found:
 		}
 	}
 
-	map->flags |= FTL_CACHED_VA | FTL_UNMAPPED;
-	map->last_va = va;
-
 	return -ERR_NOT_FOUND;
 }

source/tests/ftl/trace_path.c

@@ -24,7 +24,6 @@ static void test_empty_root(void **state)
 
 	map.log2_page_size = ilog2(4 * KIB);
 	map.root = UINT32_MAX;
-	map.flags = 0;
 
 	ret = __real_trace_path(&map, NULL, &page, 0);
 
@@ -81,7 +80,6 @@ static void test_exact_match(void **state)
 
 	map.log2_page_size = ilog2(4 * KIB);
 	map.root = 75;
-	map.flags = 0;
 
 	expect_value(__wrap_read_page_desc, map, &map);
 	expect_value(__wrap_read_page_desc, upage, 75);
@@ -149,7 +147,6 @@ static void test_walk(void **state)
 
 	map.log2_page_size = ilog2(4 * KIB);
 	map.root = 42;
-	map.flags = 0;
 
 	expect_value(__wrap_read_page_desc, map, &map);
 	expect_value(__wrap_read_page_desc, upage, 42);