spiffs_cache.c

/*
 * spiffs_cache.c
 *
 *  Created on: Jun 23, 2013
 *      Author: petera
 */

#include "spiffs.h"
#include "spiffs_nucleus.h"

#if SPIFFS_CACHE

// returns cached page for give page index, or null if no such cached page
static spiffs_cache_page *spiffs_cache_page_get(spiffs *fs, spiffs_page_ix pix) {
    spiffs_cache *cache = spiffs_get_cache(fs);
    if ((cache->cpage_use_map & cache->cpage_use_mask) == 0) return 0;
    int i;
    for (i = 0; i < cache->cpage_count; i++) {
        spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
        if ((cache->cpage_use_map & (1 << i)) &&
                (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) == 0 &&
                cp->ucache.spix.pix == pix) {
            //SPIFFS_CACHE_DBG("CACHE_GET: have cache page "_SPIPRIi" for "_SPIPRIpg"\n", i, pix);
            cp->last_access = cache->last_access;
            return cp;
        }
    }
    //SPIFFS_CACHE_DBG("CACHE_GET: no cache for "_SPIPRIpg"\n", pix);
    return 0;
}

// frees cached page
static s32_t spiffs_cache_page_free(spiffs *fs, int ix, u8_t write_back) {
    s32_t res = SPIFFS_OK;
    spiffs_cache *cache = spiffs_get_cache(fs);
    spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, ix);
    if (cache->cpage_use_map & (1 << ix)) {
        if (write_back &&
                (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) == 0 &&
                (cp->flags & SPIFFS_CACHE_FLAG_DIRTY)) {
            u8_t *mem =  spiffs_get_cache_page(fs, cache, ix);
            SPIFFS_CACHE_DBG("CACHE_FREE: write cache page "_SPIPRIi" pix "_SPIPRIpg"\n", ix, cp->ucache.spix.pix);
            res = SPIFFS_HAL_WRITE(fs, SPIFFS_PAGE_TO_PADDR(fs, cp->ucache.spix.pix), SPIFFS_CFG_LOG_PAGE_SZ(fs), mem);
        }

#if SPIFFS_CACHE_WR
        if (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) {
            SPIFFS_CACHE_DBG("CACHE_FREE: free cache page "_SPIPRIi" objid "_SPIPRIid"\n", ix, cp->ucache.swrc.obj_id);
        } else
#endif
        {
            SPIFFS_CACHE_DBG("CACHE_FREE: free cache page "_SPIPRIi" pix "_SPIPRIpg"\n", ix, cp->ucache.spix.pix);
        }
        cache->cpage_use_map &= ~(1 << ix);
        cp->flags = 0;
    }

    return res;
}

// removes the oldest accessed cached page
static s32_t spiffs_cache_page_remove_oldest(spiffs *fs, u8_t flag_mask, u8_t flags) {
    s32_t res = SPIFFS_OK;
    spiffs_cache *cache = spiffs_get_cache(fs);

    if ((cache->cpage_use_map & cache->cpage_use_mask) != cache->cpage_use_mask) {
        // at least one free cpage
        return SPIFFS_OK;
    }

    // all busy, scan thru all to find the cpage which has oldest access
    int i;
    int cand_ix = -1;
    u32_t oldest_val = 0;
    for (i = 0; i < cache->cpage_count; i++) {
        spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
        if ((cache->last_access - cp->last_access) > oldest_val &&
                (cp->flags & flag_mask) == flags) {
            oldest_val = cache->last_access - cp->last_access;
            cand_ix = i;
        }
    }

    if (cand_ix >= 0) {
        res = spiffs_cache_page_free(fs, cand_ix, 1);
    }

    return res;
}

// allocates a new cached page and returns it, or null if all cache pages are busy
static spiffs_cache_page *spiffs_cache_page_allocate(spiffs *fs) {
    spiffs_cache *cache = spiffs_get_cache(fs);
    if (cache->cpage_use_map == 0xffffffff) {
        // out of cache memory
        return 0;
    }
    int i;
    for (i = 0; i < cache->cpage_count; i++) {
        if ((cache->cpage_use_map & (1 << i)) == 0) {
            spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
            cache->cpage_use_map |= (1 << i);
            cp->last_access = cache->last_access;
            //SPIFFS_CACHE_DBG("CACHE_ALLO: allocated cache page "_SPIPRIi"\n", i);
            return cp;
        }
    }
    // out of cache entries
    return 0;
}

// drops the cache page for give page index
void spiffs_cache_drop_page(spiffs *fs, spiffs_page_ix pix) {
    spiffs_cache_page *cp =  spiffs_cache_page_get(fs, pix);
    if (cp) {
        spiffs_cache_page_free(fs, cp->ix, 0);
    }
}

// ------------------------------

// reads from spi flash or the cache
s32_t spiffs_phys_rd(
    spiffs *fs,
    u8_t op,
    spiffs_file fh,
    u32_t addr,
    u32_t len,
    u8_t *dst) {
    (void)fh;
    s32_t res = SPIFFS_OK;
    spiffs_cache *cache = spiffs_get_cache(fs);
    spiffs_cache_page *cp =  spiffs_cache_page_get(fs, SPIFFS_PADDR_TO_PAGE(fs, addr));
    cache->last_access++;
    if (cp) {
        // we've already got one, you see
#if SPIFFS_CACHE_STATS
        fs->cache_hits++;
#endif
        cp->last_access = cache->last_access;
        u8_t *mem =  spiffs_get_cache_page(fs, cache, cp->ix);
        _SPIFFS_MEMCPY(dst, &mem[SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr)], len);
    } else {
        if ((op & SPIFFS_OP_TYPE_MASK) == SPIFFS_OP_T_OBJ_LU2) {
            // for second layer lookup functions, we do not cache in order to prevent shredding
            return SPIFFS_HAL_READ(fs, addr, len, dst);
        }
#if SPIFFS_CACHE_STATS
        fs->cache_misses++;
#endif
        // this operation will always free one cache page (unless all already free),
        // the result code stems from the write operation of the possibly freed cache page
        res = spiffs_cache_page_remove_oldest(fs, SPIFFS_CACHE_FLAG_TYPE_WR, 0);

        cp = spiffs_cache_page_allocate(fs);
        if (cp) {
            cp->flags = SPIFFS_CACHE_FLAG_WRTHRU;
            cp->ucache.spix.pix = SPIFFS_PADDR_TO_PAGE(fs, addr);
            SPIFFS_CACHE_DBG("CACHE_ALLO: allocated cache page "_SPIPRIi" for pix "_SPIPRIpg "\n", cp->ix, cp->ucache.spix.pix);

            s32_t res2 = SPIFFS_HAL_READ(fs,
                                         addr - SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr),
                                         SPIFFS_CFG_LOG_PAGE_SZ(fs),
                                         spiffs_get_cache_page(fs, cache, cp->ix));
            if (res2 != SPIFFS_OK) {
                // honor read failure before possible write failure (bad idea?)
                res = res2;
            }
            u8_t *mem =  spiffs_get_cache_page(fs, cache, cp->ix);
            _SPIFFS_MEMCPY(dst, &mem[SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr)], len);
        } else {
            // this will never happen, last resort for sake of symmetry
            s32_t res2 = SPIFFS_HAL_READ(fs, addr, len, dst);
            if (res2 != SPIFFS_OK) {
                // honor read failure before possible write failure (bad idea?)
                res = res2;
            }
        }
    }
    return res;
}

// writes to spi flash and/or the cache
s32_t spiffs_phys_wr(
    spiffs *fs,
    u8_t op,
    spiffs_file fh,
    u32_t addr,
    u32_t len,
    u8_t *src) {
    (void)fh;
    spiffs_page_ix pix = SPIFFS_PADDR_TO_PAGE(fs, addr);
    spiffs_cache *cache = spiffs_get_cache(fs);
    spiffs_cache_page *cp =  spiffs_cache_page_get(fs, pix);

    if (cp && (op & SPIFFS_OP_COM_MASK) != SPIFFS_OP_C_WRTHRU) {
        // have a cache page
        // copy in data to cache page

        if ((op & SPIFFS_OP_COM_MASK) == SPIFFS_OP_C_DELE &&
                (op & SPIFFS_OP_TYPE_MASK) != SPIFFS_OP_T_OBJ_LU) {
            // page is being deleted, wipe from cache - unless it is a lookup page
            spiffs_cache_page_free(fs, cp->ix, 0);
            return SPIFFS_HAL_WRITE(fs, addr, len, src);
        }

        u8_t *mem =  spiffs_get_cache_page(fs, cache, cp->ix);
        _SPIFFS_MEMCPY(&mem[SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr)], src, len);

        cache->last_access++;
        cp->last_access = cache->last_access;

        if (cp->flags & SPIFFS_CACHE_FLAG_WRTHRU) {
            // page is being updated, no write-cache, just pass thru
            return SPIFFS_HAL_WRITE(fs, addr, len, src);
        } else {
            return SPIFFS_OK;
        }
    } else {
        // no cache page, no write cache - just write thru
        return SPIFFS_HAL_WRITE(fs, addr, len, src);
    }
}

#if SPIFFS_CACHE_WR
// returns the cache page that this fd refers, or null if no cache page
spiffs_cache_page *spiffs_cache_page_get_by_fd(spiffs *fs, spiffs_fd *fd) {
    spiffs_cache *cache = spiffs_get_cache(fs);

    if ((cache->cpage_use_map & cache->cpage_use_mask) == 0) {
        // all cpages free, no cpage cannot be assigned to obj_id
        return 0;
    }

    int i;
    for (i = 0; i < cache->cpage_count; i++) {
        spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
        if ((cache->cpage_use_map & (1 << i)) &&
                (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) &&
                cp->ucache.swrc.obj_id == fd->obj_id) {
            return cp;
        }
    }

    return 0;
}

// allocates a new cache page and refers this to given fd - flushes an old cache
// page if all cache is busy
spiffs_cache_page *spiffs_cache_page_allocate_by_fd(spiffs *fs, spiffs_fd *fd) {
    // before this function is called, it is ensured that there is no already existing
    // cache page with same object id
    spiffs_cache_page_remove_oldest(fs, SPIFFS_CACHE_FLAG_TYPE_WR, 0);
    spiffs_cache_page *cp = spiffs_cache_page_allocate(fs);
    if (cp == 0) {
        // could not get cache page
        return 0;
    }

    cp->flags = SPIFFS_CACHE_FLAG_TYPE_WR;
    cp->ucache.swrc.obj_id = fd->obj_id;
    fd->cache_page = cp;
    SPIFFS_CACHE_DBG("CACHE_ALLO: allocated cache page "_SPIPRIi" for fd "_SPIPRIfd ":"_SPIPRIid "\n", cp->ix, fd->file_nbr, fd->obj_id);
    return cp;
}

// unrefers all fds that this cache page refers to and releases the cache page
void spiffs_cache_fd_release(spiffs *fs, spiffs_cache_page *cp) {
    if (cp == 0) return;
    u32_t i;
    spiffs_fd *fds = (spiffs_fd *)fs->fd_space;
    for (i = 0; i < fs->fd_count; i++) {
        spiffs_fd *cur_fd = &fds[i];
        if (cur_fd->file_nbr != 0 && cur_fd->cache_page == cp) {
            cur_fd->cache_page = 0;
        }
    }
    spiffs_cache_page_free(fs, cp->ix, 0);

    cp->ucache.swrc.obj_id = 0;
}

#endif

// initializes the cache
void spiffs_cache_init(spiffs *fs) {
    if (fs->cache == 0) return;
    u32_t sz = fs->cache_size;
    u32_t cache_mask = 0;
    int i;
    int cache_entries =
        (sz - sizeof(spiffs_cache)) / (SPIFFS_CACHE_PAGE_SIZE(fs));
    if (cache_entries <= 0) return;

    for (i = 0; i < cache_entries; i++) {
        cache_mask <<= 1;
        cache_mask |= 1;
    }

    spiffs_cache cache;
    memset(&cache, 0, sizeof(spiffs_cache));
    cache.cpage_count = cache_entries;
    cache.cpages = (u8_t *)((u8_t *)fs->cache + sizeof(spiffs_cache));

    cache.cpage_use_map = 0xffffffff;
    cache.cpage_use_mask = cache_mask;
    _SPIFFS_MEMCPY(fs->cache, &cache, sizeof(spiffs_cache));

    spiffs_cache *c = spiffs_get_cache(fs);

    memset(c->cpages, 0, c->cpage_count * SPIFFS_CACHE_PAGE_SIZE(fs));

    c->cpage_use_map &= ~(c->cpage_use_mask);
    for (i = 0; i < cache.cpage_count; i++) {
        spiffs_get_cache_page_hdr(fs, c, i)->ix = i;
    }
}

#endif // SPIFFS_CACHE