ftl: initial implementation of the Flash Translation Layer
This commit is contained in:
parent
bd326ad795
commit
2b5225ef98
4 changed files with 682 additions and 0 deletions
642
source/ftl/ftl.c
Normal file
642
source/ftl/ftl.c
Normal file
|
|
@ -0,0 +1,642 @@
|
|||
#include <limits.h>
|
||||
#include <stdio.h>
|
||||
#include <stdint.h>
|
||||
#include <stdlib.h>
|
||||
#include <string.h>
|
||||
|
||||
#include <bitops.h>
|
||||
#include <flash.h>
|
||||
#include <ftl.h>
|
||||
#include <macros.h>
|
||||
|
||||
#define ERR_NOT_FOUND 2
|
||||
|
||||
/* Given the current user page, this function computes the page number of the
|
||||
* next user page by incrementing the page number. However, if incrementing the
|
||||
* page number results in the page number of a page containing page
|
||||
* descriptors, the page number is incremented again to have it point to the
|
||||
* first user page of the next page group. Finally, if incrementing the page
|
||||
* number results in a page number that is larger than the total amount of
|
||||
* possible pages on the devices, the page number of the very first user page
|
||||
* is returned instead.
|
||||
*/
|
||||
static uint32_t next_upage(struct ftl_journal *j, uint32_t p)
|
||||
{
|
||||
size_t log2_pages_per_block = j->log2_pages_per_group +
|
||||
j->log2_groups_per_block;
|
||||
|
||||
++p;
|
||||
|
||||
if (is_aligned(p + 1, j->log2_pages_per_group))
|
||||
++p;
|
||||
|
||||
if (p >= (j->nblocks << log2_pages_per_block))
|
||||
p = 0;
|
||||
|
||||
return p;
|
||||
}
|
||||
|
||||
/* Determines the amount of user pages to store in a page group by determining
|
||||
* how many page descriptors the last page of the page group can contain at
|
||||
* most. Because the page group consists of $2^n$ pages, $2^{n - 1}$ of those
|
||||
* pages will end up becoming user pages. Once the amount of pages in a page
|
||||
* group has been determined, the amount of page groups within an erase block
|
||||
* can also be determined, as a single page group may not cover a whole erase
|
||||
* block.
|
||||
*/
|
||||
static int find_block_div(struct ftl_journal *j)
|
||||
{
|
||||
size_t log2_pages_per_block = j->log2_block_size - j->log2_page_size;
|
||||
size_t nbytes_avail = (1 << j->log2_page_size) -
|
||||
sizeof(struct ftl_page_group);
|
||||
size_t nbytes = sizeof(struct ftl_page_desc);
|
||||
|
||||
j->log2_pages_per_group = 1;
|
||||
|
||||
while (j->log2_pages_per_group < log2_pages_per_block) {
|
||||
nbytes = 2 * nbytes + sizeof(struct ftl_page_desc);
|
||||
|
||||
if (nbytes > nbytes_avail)
|
||||
break;
|
||||
|
||||
++j->log2_pages_per_group;
|
||||
}
|
||||
|
||||
j->log2_groups_per_block = log2_pages_per_block - j->log2_pages_per_group;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Erases an entire block by erasing the smallest units that can be erased that
|
||||
* span the block.
|
||||
*/
|
||||
static int erase_block(struct ftl_journal *j, uint32_t block)
|
||||
{
|
||||
uint32_t pages_per_block = j->log2_block_size - j->log2_erase_size;
|
||||
uint32_t page = block << pages_per_block;
|
||||
uint32_t i;
|
||||
|
||||
for (i = 0; i < UINT32_C(1) << pages_per_block; ++i) {
|
||||
if (flash_erase(j->dev, page + i,
|
||||
UINT32_C(1) << j->log2_erase_size) < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void reset_journal(struct ftl_journal *j)
|
||||
{
|
||||
j->log2_erase_size = ilog2(4 * KIB);
|
||||
j->log2_page_size = ilog2(4 * KIB);
|
||||
j->log2_block_size = ilog2(64 * KIB);
|
||||
|
||||
find_block_div(j);
|
||||
|
||||
j->nblocks = flash_get_size(j->dev) >> j->log2_block_size;
|
||||
|
||||
j->head = 0;
|
||||
j->tail = 0;
|
||||
j->root = UINT32_MAX;
|
||||
j->epoch = 0;
|
||||
}
|
||||
|
||||
int ftl_init_journal(struct ftl_journal *j, struct flash_dev *dev)
|
||||
{
|
||||
j->dev = dev;
|
||||
|
||||
reset_journal(j);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Given a block number, this function attempts to find the first block that is
|
||||
* in use. A block is considered to be in use when the first page group is in
|
||||
* use, as a block can only be erased as a whole. Therefore, if the first page
|
||||
* group is not in use, neither will the other page groups in a block.
|
||||
*/
|
||||
static int find_block(struct ftl_journal *j, struct ftl_page_group *group,
|
||||
uint32_t *where, uint32_t block)
|
||||
{
|
||||
uint32_t page;
|
||||
unsigned attempt;
|
||||
|
||||
for (attempt = 0; block < j->nblocks && attempt < FTL_MAX_ATTEMPTS;
|
||||
++attempt, ++block) {
|
||||
page = block << j->log2_block_size;
|
||||
page |= ((UINT32_C(1) << j->log2_pages_per_group) - 1) << j->log2_page_size;
|
||||
|
||||
if (flash_read(j->dev, page, group, sizeof *group) < 0)
|
||||
continue;
|
||||
|
||||
if (memcmp(group->magic, "FTL", sizeof group->magic) != 0)
|
||||
continue;
|
||||
|
||||
*where = block;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
return -1;
|
||||
}
|
||||
|
||||
/* Given the block number of the first block, attempts to use binary search to
|
||||
* find the last block that is in use.
|
||||
*/
|
||||
static uint32_t find_last_block(struct ftl_journal *j, uint32_t first)
|
||||
{
|
||||
struct ftl_page_group group;
|
||||
uint32_t mid, low = first, high = j->nblocks - 1;
|
||||
uint32_t found, next;
|
||||
|
||||
while (low <= high) {
|
||||
mid = (low + high) / 2;
|
||||
|
||||
if (find_block(j, &group, &found, mid) < 0 ||
|
||||
group.epoch != j->epoch) {
|
||||
if (!mid)
|
||||
return first;
|
||||
|
||||
high = mid - 1;
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
if (((found + 1) > j->nblocks) ||
|
||||
find_block(j, &group, &next, found + 1) < 0 ||
|
||||
group.epoch != j->epoch)
|
||||
return found;
|
||||
|
||||
low = next;
|
||||
}
|
||||
|
||||
return first;
|
||||
}
|
||||
|
||||
/* Given a page number, this function checks whether the page is fully erased
|
||||
* by checking if all bits are set to ones.
|
||||
*/
|
||||
static int is_page_erased(struct ftl_journal *j, uint32_t page)
|
||||
{
|
||||
uint8_t data[64];
|
||||
size_t i, nbytes, len = j->log2_page_size;
|
||||
uint32_t addr = page << j->log2_page_size;
|
||||
|
||||
while (len) {
|
||||
nbytes = min(sizeof data, len);
|
||||
|
||||
if (flash_read(j->dev, addr, data, nbytes) < 0)
|
||||
return 0;
|
||||
|
||||
for (i = 0; i < nbytes; ++i) {
|
||||
if (data[i] != 0xff)
|
||||
return 0;
|
||||
}
|
||||
|
||||
addr += nbytes;
|
||||
len -= nbytes;
|
||||
}
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/* Given the group number, this function checks if a page group is erased by
|
||||
* checking if the pages that compose the page group are erased.
|
||||
*/
|
||||
static int is_group_erased(struct ftl_journal *j, uint32_t group)
|
||||
{
|
||||
uint32_t npages = UINT32_C(1) << j->log2_pages_per_group;
|
||||
uint32_t page = group << j->log2_pages_per_group;
|
||||
uint32_t i;
|
||||
|
||||
for (i = 0; i < npages; ++i) {
|
||||
if (!is_page_erased(j, page + i))
|
||||
return 0;
|
||||
}
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/* Attempts to find the last page group that is in use within a block by
|
||||
* performing a binary search on the page groups.
|
||||
*/
|
||||
static uint32_t find_last_group(struct ftl_journal *j, uint32_t block)
|
||||
{
|
||||
uint32_t ngroups = UINT32_C(1) << j->log2_groups_per_block;
|
||||
uint32_t mid, low = 0, high = ngroups - 1;
|
||||
|
||||
while (low <= high) {
|
||||
mid = (low + high) / 2;
|
||||
|
||||
if (is_group_erased(j, mid)) {
|
||||
high = mid - 1;
|
||||
continue;
|
||||
}
|
||||
|
||||
if (((mid + 1) >= ngroups) ||
|
||||
is_group_erased(j, mid + 1))
|
||||
return (block << j->log2_groups_per_block) + mid;
|
||||
|
||||
low = mid + 1;
|
||||
}
|
||||
|
||||
return block << j->log2_groups_per_block;
|
||||
}
|
||||
|
||||
int read_page_desc(struct ftl_journal *j,
|
||||
struct ftl_page_desc *page_desc, uint32_t upage);
|
||||
|
||||
static int find_root(struct ftl_journal *j, uint32_t group)
|
||||
{
|
||||
struct ftl_page_desc page_desc;
|
||||
uint32_t upage;
|
||||
|
||||
upage = group << j->log2_pages_per_group;
|
||||
|
||||
do {
|
||||
j->root = upage;
|
||||
upage = next_upage(j, upage);
|
||||
|
||||
if (read_page_desc(j, &page_desc, upage) < 0)
|
||||
return -1;
|
||||
/* TODO: better condition? */
|
||||
} while (page_desc.va != UINT32_MAX);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Attempts to find the first free page within a page group by looking for the
|
||||
* first page that is considered to be erased. If no such page could be found
|
||||
* within the page group, the first user page of the next page group should be
|
||||
* used as that page group should not be in use.
|
||||
*/
|
||||
static int find_head(struct ftl_journal *j)
|
||||
{
|
||||
size_t log2_pages_per_block = j->log2_pages_per_group +
|
||||
j->log2_groups_per_block;
|
||||
|
||||
j->head = j->root;
|
||||
|
||||
do {
|
||||
j->head = next_upage(j, j->head);
|
||||
|
||||
if (is_aligned(j->head, log2_pages_per_block))
|
||||
return 0;
|
||||
} while (!is_page_erased(j, j->head));
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* 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.
|
||||
*/
|
||||
int ftl_resume_journal(struct ftl_journal *j)
|
||||
{
|
||||
struct ftl_page_group group;
|
||||
uint32_t first, last, group_no;
|
||||
|
||||
if (!j)
|
||||
return -1;
|
||||
|
||||
if (find_block(j, &group, &first, 0) < 0) {
|
||||
reset_journal(j);
|
||||
|
||||
return -1;
|
||||
}
|
||||
|
||||
j->epoch = group.epoch;
|
||||
last = find_last_block(j, first);
|
||||
group_no = find_last_group(j, last);
|
||||
|
||||
if (find_root(j, group_no) < 0)
|
||||
return -1;
|
||||
|
||||
if (find_head(j) < 0)
|
||||
return -1;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Writes the page descriptor to the footer of the current page group and
|
||||
* increments the head to point to the next free user page.
|
||||
*/
|
||||
static int ftl_write_page_desc(struct ftl_journal *j,
|
||||
const struct ftl_page_desc *page_desc)
|
||||
{
|
||||
struct ftl_page_group group;
|
||||
uint32_t group_no, page, addr, offset, head;
|
||||
|
||||
group_no = j->head >> j->log2_pages_per_group;
|
||||
page = ((group_no + 1) << j->log2_pages_per_group) - 1;
|
||||
addr = page << j->log2_page_size;
|
||||
|
||||
/* Write the page group header. */
|
||||
if (is_page_erased(j, page)) {
|
||||
memcpy(&group.magic, "FTL", sizeof group.magic);
|
||||
group.epoch = j->epoch;
|
||||
group.tail = j->tail;
|
||||
|
||||
if (flash_write(j->dev, addr, &group, sizeof group) < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
offset = sizeof group + (j->head & ((1 << j->log2_pages_per_group) - 1)) *
|
||||
sizeof *page_desc;
|
||||
|
||||
if (flash_write(j->dev, addr + offset, page_desc, sizeof *page_desc) < 0)
|
||||
return -1;
|
||||
|
||||
j->root = j->head;
|
||||
|
||||
head = j->head;
|
||||
j->head = next_upage(j, j->head);
|
||||
|
||||
if (j->head < head)
|
||||
++j->epoch;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Given the page number of a user page, reads the page descriptor associated
|
||||
* with the user page by locating the footer and more specifically the page
|
||||
* descriptor within the page group.
|
||||
*/
|
||||
int read_page_desc(struct ftl_journal *j,
|
||||
struct ftl_page_desc *page_desc, uint32_t upage)
|
||||
{
|
||||
uint32_t group_no, page, addr, offset;
|
||||
|
||||
group_no = upage >> j->log2_pages_per_group;
|
||||
page = ((group_no + 1) << j->log2_pages_per_group) - 1;
|
||||
addr = page << j->log2_page_size;
|
||||
offset = sizeof(struct ftl_page_group) +
|
||||
(upage & ((1 << j->log2_pages_per_group) - 1)) * sizeof *page_desc;
|
||||
|
||||
return flash_read(j->dev, addr + offset, page_desc, sizeof *page_desc);
|
||||
}
|
||||
|
||||
/* 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
|
||||
* depth until we have either found that there is no further subtree to
|
||||
* traverse or until we have found the actual user page.
|
||||
*/
|
||||
static int trace_path(struct ftl_journal *j,
|
||||
struct ftl_page_desc *new_page_desc, uint32_t *loc, uint32_t va)
|
||||
{
|
||||
struct ftl_page_desc page_desc;
|
||||
uint8_t depth = 0;
|
||||
uint32_t upage = j->root;
|
||||
|
||||
if (new_page_desc)
|
||||
new_page_desc->va = va;
|
||||
|
||||
if (upage == UINT32_MAX)
|
||||
goto err_not_found;
|
||||
|
||||
if (read_page_desc(j, &page_desc, upage) < 0)
|
||||
return -1;
|
||||
|
||||
for (; depth < 32; ++depth) {
|
||||
if (page_desc.va == UINT32_MAX)
|
||||
goto err_not_found;
|
||||
|
||||
if (!((va ^ page_desc.va) & (1 << (32 - depth - 1)))) {
|
||||
if (new_page_desc)
|
||||
new_page_desc->subtrees[depth] = page_desc.subtrees[depth];
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
if (new_page_desc)
|
||||
new_page_desc->subtrees[depth] = upage;
|
||||
|
||||
if ((upage = page_desc.subtrees[depth]) == UINT32_MAX) {
|
||||
++depth;
|
||||
goto err_not_found;
|
||||
}
|
||||
|
||||
if (read_page_desc(j, &page_desc, upage) < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
if (loc)
|
||||
*loc = upage;
|
||||
|
||||
return 0;
|
||||
|
||||
err_not_found:
|
||||
if (new_page_desc) {
|
||||
for (; depth < 32; ++depth) {
|
||||
new_page_desc->subtrees[depth] = UINT32_MAX;
|
||||
}
|
||||
}
|
||||
|
||||
return -ERR_NOT_FOUND;
|
||||
}
|
||||
|
||||
static int ftl_write_upage(struct ftl_journal *j, const uint8_t *page,
|
||||
const struct ftl_page_desc *page_desc);
|
||||
|
||||
static int free_page(struct ftl_journal *j, uint32_t upage)
|
||||
{
|
||||
struct ftl_page_desc page_desc;
|
||||
uint32_t found_upage, va;
|
||||
|
||||
if (read_page_desc(j, &page_desc, upage) < 0)
|
||||
return -1;
|
||||
|
||||
va = page_desc.va;
|
||||
|
||||
if (trace_path(j, &page_desc, &found_upage, va) < 0)
|
||||
return -1;
|
||||
|
||||
if (upage != found_upage)
|
||||
return 0;
|
||||
|
||||
if (flash_copy(j->dev, j->head << j->log2_page_size,
|
||||
upage << j->log2_page_size, 1 << j->log2_page_size) < 0)
|
||||
return -1;
|
||||
|
||||
return ftl_write_upage(j, NULL, &page_desc);
|
||||
}
|
||||
|
||||
static int free_group(struct ftl_journal *j, uint32_t group)
|
||||
{
|
||||
uint32_t npages = UINT32_C(1) << j->log2_pages_per_group;
|
||||
uint32_t page = group << j->log2_pages_per_group;
|
||||
uint32_t i;
|
||||
|
||||
for (i = 0; i < npages; ++i) {
|
||||
if (free_page(j, page + i) < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int free_block(struct ftl_journal *j, uint32_t block)
|
||||
{
|
||||
uint32_t ngroups = UINT32_C(1) << j->log2_groups_per_block;
|
||||
uint32_t group = block << j->log2_groups_per_block;
|
||||
uint32_t i;
|
||||
|
||||
for (i = 0; i < ngroups; ++i) {
|
||||
if (free_group(j, group + i) < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int free_tail(struct ftl_journal *j)
|
||||
{
|
||||
size_t log2_pages_per_block = j->log2_pages_per_group +
|
||||
j->log2_groups_per_block;
|
||||
size_t npages = j->nblocks << log2_pages_per_block;
|
||||
size_t dist;
|
||||
|
||||
if (j->tail < j->head)
|
||||
dist = npages - j->head + j->tail;
|
||||
else
|
||||
dist = j->tail - j->head;
|
||||
|
||||
if (dist > (UINT32_C(1) << log2_pages_per_block))
|
||||
return 0;
|
||||
|
||||
if (free_block(j, j->tail >> log2_pages_per_block) < 0)
|
||||
return -1;
|
||||
|
||||
j->tail += 1 << log2_pages_per_block;
|
||||
|
||||
if (j->tail >= npages)
|
||||
j->tail -= npages;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int prepare_head(struct ftl_journal *j)
|
||||
{
|
||||
size_t log2_pages_per_block = j->log2_pages_per_group +
|
||||
j->log2_groups_per_block;
|
||||
|
||||
if (!is_aligned(j->head, log2_pages_per_block))
|
||||
return 0;
|
||||
|
||||
if (free_tail(j) < 0)
|
||||
return -1;
|
||||
|
||||
return erase_block(j, j->head >> log2_pages_per_block);
|
||||
}
|
||||
|
||||
/* Prepares the head for writing, writes the user page to the current available
|
||||
* user page and finally writes the page descriptor to the footer of the page
|
||||
* group, whereupon the head is incremented to point to the next available user
|
||||
* page.
|
||||
*/
|
||||
static int ftl_write_upage(struct ftl_journal *j, const uint8_t *page,
|
||||
const struct ftl_page_desc *page_desc)
|
||||
{
|
||||
if (prepare_head(j) < 0)
|
||||
return -1;
|
||||
|
||||
if (page && flash_write(j->dev, j->head << j->log2_page_size, page,
|
||||
j->log2_page_size) < 0)
|
||||
return -1;
|
||||
|
||||
return ftl_write_page_desc(j, page_desc);
|
||||
}
|
||||
|
||||
int ftl_find(struct ftl_journal *j, uint32_t *page, uint32_t va)
|
||||
{
|
||||
return trace_path(j, NULL, page, va);
|
||||
}
|
||||
|
||||
int ftl_read(struct ftl_journal *j, uint8_t *data, uint32_t va)
|
||||
{
|
||||
int ret;
|
||||
uint32_t page;
|
||||
|
||||
if ((ret = ftl_find(j, &page, va)) < 0) {
|
||||
if (ret != -ERR_NOT_FOUND)
|
||||
return -1;
|
||||
|
||||
memset(data, 0, j->log2_page_size);
|
||||
return 0;
|
||||
}
|
||||
|
||||
return flash_read(j->dev, page << j->log2_page_size, data,
|
||||
j->log2_page_size);
|
||||
}
|
||||
|
||||
int ftl_write(struct ftl_journal *j, uint32_t va, const uint8_t *data)
|
||||
{
|
||||
struct ftl_page_desc page_desc;
|
||||
int ret;
|
||||
|
||||
if (va >= ftl_get_capacity(j) &&
|
||||
!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;
|
||||
}
|
||||
|
||||
return ftl_write_upage(j, data, &page_desc);
|
||||
}
|
||||
|
||||
int ftl_trim(struct ftl_journal *j, uint32_t va)
|
||||
{
|
||||
struct ftl_page_desc page_desc, alt_page_desc;
|
||||
size_t level, i;
|
||||
uint32_t alt_va, page;
|
||||
int ret;
|
||||
|
||||
if ((ret = trace_path(j, &page_desc, &page, va)) < 0) {
|
||||
if (ret == -ERR_NOT_FOUND)
|
||||
return 0;
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
for (i = 0; i < 32; ++i) {
|
||||
level = 32 - i - 1;
|
||||
|
||||
if ((alt_va = page_desc.subtrees[level]) != UINT32_MAX)
|
||||
break;
|
||||
}
|
||||
|
||||
if (i == 32) {
|
||||
j->root = UINT32_MAX;
|
||||
/* TODO: how do we clean the FTL? */
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
if (read_page_desc(j, &alt_page_desc, alt_va) < 0)
|
||||
return -1;
|
||||
|
||||
page_desc.va = alt_page_desc.va;
|
||||
page_desc.subtrees[level] = UINT32_MAX;
|
||||
|
||||
for (i = level + 1; i < 32; ++i) {
|
||||
page_desc.subtrees[i] = alt_page_desc.subtrees[i];
|
||||
}
|
||||
|
||||
if (flash_copy(j->dev, j->head << j->log2_page_size,
|
||||
page << j->log2_page_size, 1 << j->log2_page_size) < 0)
|
||||
return -1;
|
||||
|
||||
return ftl_write_upage(j, NULL, &page_desc);
|
||||
}
|
||||
|
||||
/* The capacity of the device is the total amount of user pages minus a block
|
||||
* worth of user pages for garbage collection.
|
||||
*/
|
||||
uint32_t ftl_get_capacity(const struct ftl_journal *j)
|
||||
{
|
||||
return ((j->nblocks - 1) << j->log2_block_size) -
|
||||
((j->nblocks - 1) << j->log2_page_size);
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue