*/
INLINE void battfs_to_disk(struct BattFsPageHeader *hdr, uint8_t *buf)
{
- STATIC_ASSERT(BATTFS_HEADER_LEN == 10);
+ STATIC_ASSERT(BATTFS_HEADER_LEN == 12);
buf[0] = hdr->inode;
buf[1] = hdr->fill;
buf[4] = hdr->pgoff >> 8;
/*
- * Sequence number is at least 1 bit longer than page address.
- * Needed to take care of wraparonds.
+ * Sequence number is 40 bits long.
+ * No need to take care of wraparonds: the memory will die first!
*/
buf[5] = hdr->seq;
buf[6] = hdr->seq >> 8;
-
- /*
- * First bit used by seq.
- * Unused bits are set to 1.
- */
- buf[7] = (hdr->seq >> 16) ? 0xFF : 0xFE;
+ buf[7] = hdr->seq >> 16;
+ buf[8] = hdr->seq >> 24;
+ buf[9] = hdr->seq >> 32;
/*
* This field must be the last one!
* This is needed because if the page is only partially
* written, we can use this to detect it.
*/
- buf[8] = hdr->fcs;
- buf[9] = hdr->fcs >> 8;
+ buf[10] = hdr->fcs;
+ buf[11] = hdr->fcs >> 8;
}
/**
*/
INLINE void disk_to_battfs(uint8_t *buf, struct BattFsPageHeader *hdr)
{
- STATIC_ASSERT(BATTFS_HEADER_LEN == 10);
+ STATIC_ASSERT(BATTFS_HEADER_LEN == 12);
hdr->inode = buf[0];
hdr->fill = buf[2] << 8 | buf[1];
hdr->pgoff = buf[4] << 8 | buf[3];
- hdr->seq = (seq_t)(buf[7] & 0x01) << 16 | buf[6] << 8 | buf[5];
- hdr->fcs = buf[9] << 8 | buf[8];
+ hdr->seq = (seq_t)buf[9] << 32 | (seq_t)buf[8] << 24 | (seq_t)buf[7] << 16 | buf[6] << 8 | buf[5];
+ hdr->fcs = buf[11] << 8 | buf[10];
}
/**
if (hdr.fcs == computeFcs(&hdr))
{
/* Compute array position */
- pgcnt_t array_pos_start = countPages(filelen_table, hdr.inode);
- pgcnt_t array_pos = array_pos_start + hdr.pgoff;
+ pgcnt_t array_pos = countPages(filelen_table, hdr.inode);
+ array_pos += hdr.pgoff;
+
- /* Find the first free position */
- while (disk->page_array[array_pos] != PAGE_UNSET_SENTINEL)
+ /* Check if position is already used by another page of the same file */
+ if (disk->page_array[array_pos] == PAGE_UNSET_SENTINEL)
+ disk->page_array[array_pos] = page;
+ else
{
- ASSERT(array_pos < array_pos_start + filelen_table[hdr.inode] + filelen_table[hdr.inode + 1]);
- array_pos++;
- }
+ BattFsPageHeader hdr_prv;
+
+ if (!battfs_readHeader(disk, disk->page_array[array_pos], &hdr_prv))
+ return false;
+
+ /* Check header FCS */
+ ASSERT(hdr_prv.fcs == computeFcs(&hdr_prv));
+
+ /* Only the very same page with a different seq number can be here */
+ ASSERT(hdr.inode == hdr_prv.inode);
+ ASSERT(hdr.pgoff == hdr_prv.pgoff);
+ ASSERT(hdr.seq != hdr_prv.seq);
+
+ pgcnt_t new_page, old_page;
+ fill_t old_fill;
+
+ /*
+ * Sequence number comparison: since
+ * seq is 40 bits wide, it wraps once
+ * every 1.1E12 times.
+ * The memory will not live enough to
+ * see a wraparound, so we can use a simple
+ * compare here.
+ */
+ if (hdr.seq > hdr_prv.seq)
+ {
+ /* Current header is newer than the previuos one */
+ old_page = disk->page_array[array_pos];
+ new_page = page;
+ old_fill = hdr_prv.fill;
+ }
+ else
+ {
+ /* Previous header is newer than the current one */
+ old_page = page;
+ new_page = disk->page_array[array_pos];
+ old_fill = hdr.fill;
+ }
+
+ /* Set new page */
+ disk->page_array[array_pos] = new_page;
+ /* Add free space */
+ disk->free_bytes += old_fill;
+ /* Shift all array one position to the left, overwriting duplicate page */
+ array_pos -= hdr.pgoff;
+ array_pos += filelen_table[hdr.inode];
+ movePages(disk, array_pos, -1);
+ /* Move back all indexes */
+ filelen_table[hdr.inode]--;
+ disk->free_page_start--;
+ curr_free_page--;
+ /* Set old page as free */
+ ASSERT(disk->page_array[curr_free_page] == PAGE_UNSET_SENTINEL);
+ disk->page_array[curr_free_page++] = old_page;
- disk->page_array[array_pos] = page;
+ }
}
else
{
return true;
}
+#if 0
/**
* Find the latest version of a page, starting from the
* page supplied by \a page_array.
return true;
}
-
+#endif
/**
* Initialize and mount disk described by
return false;
}
- if (!dropOldPages(disk))
- {
- LOG_ERR("error dropping old pages\n");
- return false;
- }
-
/* Init list for opened files. */
LIST_INIT(&disk->file_opened_list);
return true;
typedef uint16_t pgcnt_t; ///< Type for counting pages on disk
typedef pgcnt_t pgoff_t; ///< Type for counting pages inside a file
typedef uint8_t inode_t; ///< Type for file inodes
-typedef uint32_t seq_t; ///< Type for page seq number
+typedef uint64_t seq_t; ///< Type for page seq number, at least 40bits wide.
typedef rotating_t fcs_t; ///< Type for header FCS.
-/**
- * Size required for free block allocation is at least 1 bit more
- * than page addressing.
- */
-STATIC_ASSERT(sizeof(seq_t) > sizeof(pgcnt_t));
/**
* BattFS page header, used to represent a page
inode_t inode; ///< File inode (file identifier).
fill_t fill; ///< Filled bytes in page.
pgoff_t pgoff; ///< Page offset inside file.
- seq_t seq; ///< Page sequence number.
+
+ /**
+ * Page sequence number.
+ * Every time a page is rewritten the seq number is
+ * increased by 1. seq_t is wide enough to not to perform
+ * a wrap around before the memory death.
+ * So it can be kept as it would be
+ * monotonically increasing for our needs.
+ */
+ seq_t seq;
/**
* FCS (Frame Check Sequence) of the page header.
* \see battfs_to_disk
* \see disk_to_battfs
*/
-#define BATTFS_HEADER_LEN 10
-
-/**
- * Half-size of page sequence numer.
- */
-#define HALF_SEQ (1 << (CPU_BITS_PER_CHAR * sizeof(pgcnt_t)))
-
-/**
- * Max sequence number.
- */
-#define MAX_SEQ ((1 << (CPU_BITS_PER_CHAR * sizeof(pgcnt_t) + 1)) - 1)
-
+#define BATTFS_HEADER_LEN 12
/**
* Maximum page address.
*/
#define PAGE_UNSET_SENTINEL ((1 << (CPU_BITS_PER_CHAR * sizeof(pgcnt_t))) - 1)
-/** Also used as an error marker sometimes */
-#define PAGE_ERROR PAGE_UNSET_SENTINEL
-
/**
* Type interface for disk init function.
* \return true if all is ok, false otherwise.
/* TODO add other fields. */
} BattFsSuper;
-typedef uint8_t filemode_t; ///< Type for file open modes.
+typedef uint8_t filemode_t; ///< Type for file open modes.
typedef int32_t file_size_t; ///< Type for file sizes.
/**
projects / bertos.git / commitdiff