parent
a899f35562
commit
770860d621
@ -0,0 +1,130 @@ |
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#include <flash.h> |
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#include <ftl.h> |
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#include <macros.h> |
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|
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#include "gc.h" |
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|
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int read_page_desc(struct ftl_journal *j, |
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struct ftl_page_desc *page_desc, uint32_t upage); |
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int trace_path(struct ftl_journal *j, |
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struct ftl_page_desc *new_page_desc, uint32_t *loc, uint32_t va); |
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int write_upage(struct ftl_journal *j, const uint8_t *page, |
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const struct ftl_page_desc *page_desc); |
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|
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/* For a given user page, attempt to claim more free space by checking if no
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* recent mapping has obsoleted the older mapping. If a more recent mapping |
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* exists, the page can be safely ignored and erased. Otherwise, we preserve |
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* the page by copying the page to create a new mapping such that the old page |
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* can be ignored and erased. |
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*/ |
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static int free_page(struct ftl_journal *j, uint32_t upage) |
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{ |
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struct ftl_page_desc page_desc; |
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uint32_t found_upage, va; |
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if (read_page_desc(j, &page_desc, upage) < 0) |
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return -1; |
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va = page_desc.va; |
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if (trace_path(j, &page_desc, &found_upage, va) < 0) |
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return -1; |
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if (upage != found_upage) |
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return 0; |
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page_desc.nused_pages = j->nused_pages; |
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if (flash_copy(j->dev, j->head << j->log2_page_size, |
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upage << j->log2_page_size, 1 << j->log2_page_size) < 0) |
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return -1; |
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return write_upage(j, NULL, &page_desc); |
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} |
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|
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/* Claim more free space by checking which user pages in a page group are
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* mapped and for which the mappings have been obsoleted by a more recent |
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* mapping. The mapped user pages are preserved by copying. |
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*/ |
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static int free_group(struct ftl_journal *j, uint32_t group) |
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{ |
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uint32_t npages = UINT32_C(1) << j->log2_pages_per_group; |
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uint32_t page = group << j->log2_pages_per_group; |
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uint32_t i; |
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for (i = 0; i < npages; ++i) { |
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if (free_page(j, page + i) < 0) |
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return -1; |
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} |
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return 0; |
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} |
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|
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/* Claim more free space by checking which user pages in a block are mapped and
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* for which the mappings have been obsoleted by a more recent mapping. The |
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* mapped user pages are preserved by copying. |
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*/ |
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static int free_block(struct ftl_journal *j, uint32_t block) |
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{ |
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uint32_t ngroups = UINT32_C(1) << j->log2_groups_per_block; |
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uint32_t group = block << j->log2_groups_per_block; |
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uint32_t i; |
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for (i = 0; i < ngroups; ++i) { |
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if (free_group(j, group + i) < 0) |
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return -1; |
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} |
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return 0; |
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} |
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|
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/* Checks if there are sufficient pages available for writing. Otherwise this
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* function attempts to claim more free space from unmapped pages for which |
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* newer pages have obsoleted the mapping. Further, we move the user pages that |
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* are still mapped as these should be preserved. |
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*/ |
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static int free_tail(struct ftl_journal *j) |
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{ |
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size_t log2_pages_per_block = j->log2_pages_per_group + |
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j->log2_groups_per_block; |
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size_t npages = j->nblocks << log2_pages_per_block; |
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size_t dist; |
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if (j->head < j->tail) |
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dist = j->tail - j->head; |
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else |
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dist = npages - j->head + j->tail; |
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if (dist > (UINT32_C(1) << log2_pages_per_block)) |
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return 0; |
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if (free_block(j, j->tail >> log2_pages_per_block) < 0) |
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return -1; |
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j->tail += 1 << log2_pages_per_block; |
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if (j->tail >= npages) |
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j->tail -= npages; |
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return 0; |
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} |
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|
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/* Prepare the head for writing. If the user page to be written to is not
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* aligned on a block boundary, the block must already be erased and there is |
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* nothing to be done. Otherwise, we free the tail if necessary and erase the |
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* block for writing. |
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*/ |
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int prepare_head(struct ftl_journal *j) |
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{ |
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size_t log2_pages_per_block = j->log2_pages_per_group + |
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j->log2_groups_per_block; |
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if (!is_aligned(j->head, log2_pages_per_block)) |
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return 0; |
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if (free_tail(j) < 0) |
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return -1; |
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return flash_erase(j->dev, j->head >> log2_pages_per_block, |
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j->log2_block_size); |
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} |
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@ -0,0 +1,3 @@ |
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#pragma once |
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int prepare_head(struct ftl_journal *j); |
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@ -0,0 +1,456 @@ |
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#include <stdlib.h> |
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#include <string.h> |
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#include <bitops.h> |
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#include <flash.h> |
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#include <ftl.h> |
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#include <macros.h> |
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#include "gc.h" |
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#include "map.h" |
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/* Given a page number, this function checks whether the page is fully erased
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* by checking if all bits are set to ones. |
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*/ |
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static int is_page_erased(struct ftl_journal *j, uint32_t page) |
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{ |
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uint8_t data[64]; |
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size_t i, nbytes, len = j->log2_page_size; |
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uint32_t addr = page << j->log2_page_size; |
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while (len) { |
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nbytes = min(sizeof data, len); |
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if (flash_read(j->dev, addr, data, nbytes) < 0) |
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return 0; |
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for (i = 0; i < nbytes; ++i) { |
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if (data[i] != 0xff) |
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return 0; |
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} |
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addr += nbytes; |
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len -= nbytes; |
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} |
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return 1; |
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} |
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/* Given the group number, this function checks if a page group is erased by
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* checking if the pages that compose the page group are erased. |
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*/ |
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static int is_group_erased(struct ftl_journal *j, uint32_t group) |
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{ |
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uint32_t npages = UINT32_C(1) << j->log2_pages_per_group; |
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uint32_t page = group << j->log2_pages_per_group; |
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uint32_t i; |
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for (i = 0; i < npages; ++i) { |
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if (!is_page_erased(j, page + i)) |
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return 0; |
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} |
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return 1; |
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} |
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|
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/* Given the current user page, this function computes the page number of the
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* next user page by incrementing the page number. However, if incrementing the |
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* page number results in the page number of a page containing page |
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* descriptors, the page number is incremented again to have it point to the |
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* first user page of the next page group. Finally, if incrementing the page |
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* number results in a page number that is larger than the total amount of |
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* possible pages on the devices, the page number of the very first user page |
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* is returned instead. |
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*/ |
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static uint32_t next_upage(struct ftl_journal *j, uint32_t p) |
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{ |
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size_t log2_pages_per_block = j->log2_pages_per_group + |
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j->log2_groups_per_block; |
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++p; |
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if (is_aligned(p + 1, j->log2_pages_per_group)) |
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++p; |
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if (p >= (j->nblocks << log2_pages_per_block)) |
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p = 0; |
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return p; |
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} |
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/* Reads the header of the given page group.
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*/ |
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int read_page_group(struct ftl_journal *j, |
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struct ftl_page_group *group, uint32_t group_no) |
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{ |
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uint32_t page, addr; |
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page = ((group_no + 1) << j->log2_pages_per_group) - 1; |
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addr = page << j->log2_page_size; |
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return flash_read(j->dev, addr, group, sizeof *group); |
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} |
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/* Given the page number of a user page, reads the page descriptor associated
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* with the user page by locating the footer and more specifically the page |
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* descriptor within the page group. |
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*/ |
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int read_page_desc(struct ftl_journal *j, |
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struct ftl_page_desc *page_desc, uint32_t upage) |
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{ |
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uint32_t group_no, page, addr, offset; |
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group_no = upage >> j->log2_pages_per_group; |
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page = ((group_no + 1) << j->log2_pages_per_group) - 1; |
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addr = page << j->log2_page_size; |
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offset = sizeof(struct ftl_page_group) + |
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(upage & ((1 << j->log2_pages_per_group) - 1)) * sizeof *page_desc; |
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return flash_read(j->dev, addr + offset, page_desc, sizeof *page_desc); |
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} |
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/* Writes the page descriptor to the footer of the current page group and
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* increments the head to point to the next free user page. |
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*/ |
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static int write_page_desc(struct ftl_journal *j, |
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const struct ftl_page_desc *page_desc) |
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{ |
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struct ftl_page_group group; |
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uint32_t group_no, page, addr, offset, head; |
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group_no = j->head >> j->log2_pages_per_group; |
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page = ((group_no + 1) << j->log2_pages_per_group) - 1; |
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addr = page << j->log2_page_size; |
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/* Write the page group header. */ |
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if (is_page_erased(j, page)) { |
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memcpy(&group.magic, "FTL", sizeof group.magic); |
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group.epoch = j->epoch; |
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group.tail = j->tail; |
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if (flash_write(j->dev, addr, &group, sizeof group) < 0) |
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return -1; |
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} |
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offset = sizeof group + (j->head & ((1 << j->log2_pages_per_group) - 1)) * |
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sizeof *page_desc; |
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if (flash_write(j->dev, addr + offset, page_desc, sizeof *page_desc) < 0) |
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return -1; |
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j->root = j->head; |
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head = j->head; |
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j->head = next_upage(j, j->head); |
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if (j->head < head) |
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++j->epoch; |
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return 0; |
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} |
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/* Prepares the head for writing, writes the user page to the current available
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* user page and finally writes the page descriptor to the footer of the page |
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* group, whereupon the head is incremented to point to the next available user |
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* page. |
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*/ |
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int write_upage(struct ftl_journal *j, const uint8_t *page, |
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const struct ftl_page_desc *page_desc) |
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{ |
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if (prepare_head(j) < 0) |
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return -1; |
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if (page && flash_write(j->dev, j->head << j->log2_page_size, page, |
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j->log2_page_size) < 0) |
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return -1; |
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return write_page_desc(j, page_desc); |
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} |
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/* Determines the amount of user pages to store in a page group by determining
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* how many page descriptors the last page of the page group can contain at |
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* most. Because the page group consists of $2^n$ pages, $2^{n - 1}$ of those |
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* pages will end up becoming user pages. Once the amount of pages in a page |
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* group has been determined, the amount of page groups within an erase block |
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* can also be determined, as a single page group may not cover a whole erase |
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* block. |
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*/ |
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static int find_block_div(struct ftl_journal *j) |
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{ |
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size_t log2_pages_per_block = j->log2_block_size - j->log2_page_size; |
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size_t nbytes_avail = (1 << j->log2_page_size) - |
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sizeof(struct ftl_page_group); |
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size_t nbytes = sizeof(struct ftl_page_desc); |
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j->log2_pages_per_group = 1; |
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while (j->log2_pages_per_group < log2_pages_per_block) { |
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nbytes = 2 * nbytes + sizeof(struct ftl_page_desc); |
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if (nbytes > nbytes_avail) |
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break; |
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++j->log2_pages_per_group; |
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} |
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j->log2_groups_per_block = log2_pages_per_block - j->log2_pages_per_group; |
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return 0; |
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} |
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/* Given a block number, this function attempts to find the first block that is
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* in use. A block is considered to be in use when the first page group is in |
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* use, as a block can only be erased as a whole. Therefore, if the first page |
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* group is not in use, neither will the other page groups in a block. |
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*/ |
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static int find_block(struct ftl_journal *j, struct ftl_page_group *group, |
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uint32_t *where, uint32_t block) |
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{ |
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uint32_t page; |
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unsigned attempt; |
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for (attempt = 0; block < j->nblocks && attempt < FTL_MAX_ATTEMPTS; |
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++attempt, ++block) { |
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page = block << j->log2_block_size; |
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page |= ((UINT32_C(1) << j->log2_pages_per_group) - 1) << j->log2_page_size; |
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if (flash_read(j->dev, page, group, sizeof *group) < 0) |
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continue; |
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if (memcmp(group->magic, "FTL", sizeof group->magic) != 0) |
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continue; |
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*where = block; |
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return 0; |
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} |
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return -1; |
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} |
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/* Given the block number of the first block, attempts to use binary search to
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* find the last block that is in use. |
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*/ |
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static uint32_t find_last_block(struct ftl_journal *j, uint32_t first) |
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{ |
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struct ftl_page_group group; |
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uint32_t mid, low = first, high = j->nblocks - 1; |
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uint32_t found, next; |
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while (low <= high) { |
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mid = (low + high) / 2; |
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if (find_block(j, &group, &found, mid) < 0 || |
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group.epoch != j->epoch) { |
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if (!mid) |
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return first; |
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high = mid - 1; |
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continue; |
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} |
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if (((found + 1) > j->nblocks) || |
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find_block(j, &group, &next, found + 1) < 0 || |
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group.epoch != j->epoch) |
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return found; |
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low = next; |
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} |
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return first; |
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} |
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/* Attempts to find the last page group that is in use within a block by
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* performing a binary search on the page groups. |
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*/ |
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static uint32_t find_last_group(struct ftl_journal *j, uint32_t block) |
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{ |
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uint32_t ngroups = UINT32_C(1) << j->log2_groups_per_block; |
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uint32_t mid, low = 0, high = ngroups - 1; |
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while (low <= high) { |
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mid = (low + high) / 2; |
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if (is_group_erased(j, mid)) { |
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high = mid - 1; |
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continue; |
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} |
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if (((mid + 1) >= ngroups) || |
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is_group_erased(j, mid + 1)) |
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return (block << j->log2_groups_per_block) + mid; |
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low = mid + 1; |
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} |
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return block << j->log2_groups_per_block; |
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} |
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static int find_root(struct ftl_journal *j, uint32_t group) |
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{ |
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struct ftl_page_desc page_desc; |
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uint32_t upage; |
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upage = group << j->log2_pages_per_group; |
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do { |
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j->root = upage; |
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upage = next_upage(j, upage); |
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if (read_page_desc(j, &page_desc, upage) < 0) |
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return -1; |
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} while (page_desc.va != UINT32_MAX || |
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page_desc.nused_pages == 0); |
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return 0; |
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} |
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/* Attempts to find the first free page within a page group by looking for the
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* first page that is considered to be erased. If no such page could be found |
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* within the page group, the first user page of the next page group should be |
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* used as that page group should not be in use. |
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*/ |
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static int find_head(struct ftl_journal *j) |
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{ |
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size_t log2_pages_per_block = j->log2_pages_per_group + |
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j->log2_groups_per_block; |
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j->head = j->root; |
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do { |
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j->head = next_upage(j, j->head); |
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if (is_aligned(j->head, log2_pages_per_block)) |
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return 0; |
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} while (!is_page_erased(j, j->head)); |
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return 0; |
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} |
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static void reset_journal(struct ftl_journal *j) |
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{ |
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j->log2_erase_size = ilog2(4 * KIB); |
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j->log2_page_size = ilog2(4 * KIB); |
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j->log2_block_size = ilog2(64 * KIB); |
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find_block_div(j); |
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j->nblocks = flash_get_size(j->dev) >> j->log2_block_size; |
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j->head = 0; |
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j->tail = 0; |
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j->root = UINT32_MAX; |
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j->nused_pages = 0; |
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j->epoch = 0; |
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} |
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int ftl_init_journal(struct ftl_journal *j, struct flash_dev *dev) |
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{ |
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j->dev = dev; |
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reset_journal(j); |
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return 0; |
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} |
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/* Resumes the journal by finding the first block that is in use, the last
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* block that is in use, the last page group that is in use, and setting the |
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* head to the first free user page. |
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*/ |
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int ftl_resume_journal(struct ftl_journal *j) |
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{ |
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struct ftl_page_group group; |
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struct ftl_page_desc page_desc; |
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uint32_t first, last, group_no; |
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if (!j) |
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return -1; |
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if (find_block(j, &group, &first, 0) < 0) { |
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reset_journal(j); |
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return -1; |
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} |
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j->epoch = group.epoch; |
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last = find_last_block(j, first); |
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group_no = find_last_group(j, last); |
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if (find_root(j, group_no) < 0) |
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return -1; |
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if (find_head(j) < 0) |
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return -1; |
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if (read_page_group(j, &group, j->root >> j->log2_pages_per_group) < 0) |
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return -1; |
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if (read_page_desc(j, &page_desc, j->root) < 0) |
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return -1; |
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j->tail = group.tail; |
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j->nused_pages = page_desc.nused_pages; |
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return 0; |
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} |
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|
||||
/* 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. |
||||
*/ |
||||
int trace_path(struct ftl_journal *j, struct ftl_page_desc *new_page_desc, |
||||
uint32_t *page, 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 (page) |
||||
*page = 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; |
||||
} |
||||
@ -0,0 +1,12 @@ |
||||
#pragma once |
||||
|
||||
#define ERR_NOT_FOUND 2 |
||||
|
||||
int read_page_group(struct ftl_journal *j, |
||||
struct ftl_page_group *group, uint32_t group_no); |
||||
int read_page_desc(struct ftl_journal *j, |
||||
struct ftl_page_desc *page_desc, uint32_t upage); |
||||
int write_upage(struct ftl_journal *j, const uint8_t *page, |
||||
const struct ftl_page_desc *page_desc); |
||||
int trace_path(struct ftl_journal *j, struct ftl_page_desc *new_page_desc, |
||||
uint32_t *page, uint32_t va); |
||||
Loading…
Reference in new issue