ftl: add ftl_get_size(), allow trimming final sector, recover tail and size

include/ftl.h

@@ -8,6 +8,7 @@ struct ftl_page_group {
 
 struct ftl_page_desc {
 	uint32_t va;
+	uint32_t nused_pages;
 	uint32_t subtrees[32];
 } __attribute__((packed));
 
@@ -15,6 +16,7 @@ struct ftl_journal {
 	struct flash_dev *dev;
 	uint32_t head, tail;
 	uint32_t root;
+	uint32_t nused_pages;
 	uint32_t nblocks;
 	uint8_t log2_groups_per_block;
 	uint8_t log2_pages_per_group;
@@ -32,4 +34,5 @@ int ftl_find(struct ftl_journal *j, uint32_t *loc, uint32_t va);
 int ftl_write(struct ftl_journal *j, uint32_t addr, const uint8_t *data);
 int ftl_read(struct ftl_journal *j, uint8_t *data, uint32_t va);
 int ftl_trim(struct ftl_journal *j, uint32_t va);
+uint32_t ftl_get_size(const struct ftl_journal *j);
 uint32_t ftl_get_capacity(const struct ftl_journal *j);

source/ftl/ftl.c

@@ -98,6 +98,7 @@ static void reset_journal(struct ftl_journal *j)
 	j->head = 0;
 	j->tail = 0;
 	j->root = UINT32_MAX;
+	j->nused_pages = 0;
 	j->epoch = 0;
 }
 
@@ -259,8 +260,8 @@ static int find_root(struct ftl_journal *j, uint32_t group)
 
 		if (read_page_desc(j, &page_desc, upage) < 0)
 			return -1;
-	/* TODO: better condition? */
-	} while (page_desc.va != UINT32_MAX);
+	} while (page_desc.va != UINT32_MAX ||
+	         page_desc.nused_pages == 0);
 
 	return 0;
 }
@@ -287,6 +288,9 @@ static int find_head(struct ftl_journal *j)
 	return 0;
 }
 
+int read_page_group(struct ftl_journal *j,
+	struct ftl_page_group *group, uint32_t group_no);
+
 /* Resumes the journal by finding the first block that is in use, the last
  * block that is in use, the last page group that is in use, and setting the
  * head to the first free user page.
@@ -294,6 +298,7 @@ static int find_head(struct ftl_journal *j)
 int ftl_resume_journal(struct ftl_journal *j)
 {
 	struct ftl_page_group group;
+	struct ftl_page_desc page_desc;
 	uint32_t first, last, group_no;
 
 	if (!j)
@@ -315,6 +320,15 @@ int ftl_resume_journal(struct ftl_journal *j)
 	if (find_head(j) < 0)
 		return -1;
 
+	if (read_page_group(j, &group, j->root >> j->log2_pages_per_group) < 0)
+		return -1;
+
+	if (read_page_desc(j, &page_desc, j->root) < 0)
+		return -1;
+
+	j->tail = group.tail;
+	j->nused_pages = page_desc.nused_pages;
+
 	return 0;
 }
 
@@ -376,6 +390,17 @@ int read_page_desc(struct ftl_journal *j,
 	return flash_read(j->dev, addr + offset, page_desc, sizeof *page_desc);
 }
 
+int read_page_group(struct ftl_journal *j,
+	struct ftl_page_group *group, uint32_t group_no)
+{
+	uint32_t page, addr;
+
+	page = ((group_no + 1) << j->log2_pages_per_group) - 1;
+	addr = page << j->log2_page_size;
+
+	return flash_read(j->dev, addr, group, sizeof *group);
+}
+
 /* Trace a path for a given virtual target address by comparing each of the
  * bits in the target address with the virtual address of our root. In case of
  * a mismatch, we proceed our traversal with the given subtree at the current
@@ -461,6 +486,8 @@ static int free_page(struct ftl_journal *j, uint32_t upage)
 	if (upage != found_upage)
 		return 0;
 
+	page_desc.nused_pages = j->nused_pages;
+
 	if (flash_copy(j->dev, j->head << j->log2_page_size,
 		upage << j->log2_page_size, 1 << j->log2_page_size) < 0)
 		return -1;
@@ -603,10 +630,14 @@ int ftl_write(struct ftl_journal *j, uint32_t va, const uint8_t *data)
 	    !is_aligned(va, 1 << j->log2_page_size))
 		return -1;
 
-	if ((ret = trace_path(j, &page_desc, NULL, va)) < 0) {
-		if (ret != -ERR_NOT_FOUND)
-			return -1;
-	}
+	if ((ret = trace_path(j, &page_desc, NULL, va)) < 0 &&
+		ret != -ERR_NOT_FOUND)
+		return -1;
+
+	if (ret == -ERR_NOT_FOUND)
+		++j->nused_pages;
+
+	page_desc.nused_pages = j->nused_pages;
 
 	return ftl_write_upage(j, data, &page_desc);
 }
@@ -625,6 +656,8 @@ int ftl_trim(struct ftl_journal *j, uint32_t va)
 		return ret;
 	}
 
+	--j->nused_pages;
+
 	for (i = 0; i < 32; ++i) {
 		level = 32 - i - 1;
 
@@ -643,6 +676,7 @@ int ftl_trim(struct ftl_journal *j, uint32_t va)
 		return -1;
 
 	page_desc.va = alt_page_desc.va;
+	page_desc.nused_pages = j->nused_pages;
 	page_desc.subtrees[level] = UINT32_MAX;
 
 	for (i = level + 1; i < 32; ++i) {
@@ -656,6 +690,14 @@ int ftl_trim(struct ftl_journal *j, uint32_t va)
 	return ftl_write_upage(j, NULL, &page_desc);
 }
 
+/* Returns the amount of used pages with a unique virtual address multiplied by
+ * the page size as the size of used space on the device.
+ */
+uint32_t ftl_get_size(const struct ftl_journal *j)
+{
+	return j->nused_pages << j->log2_page_size;
+}
+
 /* The capacity of the device is the total amount of user pages minus a block
  * worth of user pages for garbage collection.
  */