diff --git a/lfs.c b/lfs.c index aed1b072..dbcf0f02 100644 --- a/lfs.c +++ b/lfs.c @@ -596,42 +596,48 @@ static int lfs_rawunmount(lfs_t *lfs); #ifndef LFS_READONLY static int lfs_alloc_lookahead(void *p, lfs_block_t block) { lfs_t *lfs = (lfs_t*)p; - lfs_block_t off = ((block - lfs->free.off) + lfs_block_t off = ((block - lfs->lookahead.start) + lfs->block_count) % lfs->block_count; - if (off < lfs->free.size) { - lfs->free.buffer[off / 32] |= 1U << (off % 32); + if (off < lfs->lookahead.size) { + lfs->lookahead.buffer[off / 8] |= 1U << (off % 8); } return 0; } #endif -// indicate allocated blocks have been committed into the filesystem, this -// is to prevent blocks from being garbage collected in the middle of a -// commit operation -static void lfs_alloc_ack(lfs_t *lfs) { - lfs->free.ack = lfs->block_count; +// allocations should call this when all allocated blocks are committed to +// the filesystem +// +// after a checkpoint, the block allocator may realloc any untracked blocks +static void lfs_alloc_ckpoint(lfs_t *lfs) { + lfs->lookahead.ckpoint = lfs->block_count; } // drop the lookahead buffer, this is done during mounting and failed // traversals in order to avoid invalid lookahead state static void lfs_alloc_drop(lfs_t *lfs) { - lfs->free.size = 0; - lfs->free.i = 0; - lfs_alloc_ack(lfs); + lfs->lookahead.size = 0; + lfs->lookahead.next = 0; + lfs_alloc_ckpoint(lfs); } #ifndef LFS_READONLY static int lfs_fs_rawgc(lfs_t *lfs) { - // Move free offset at the first unused block (lfs->free.i) - // lfs->free.i is equal lfs->free.size when all blocks are used - lfs->free.off = (lfs->free.off + lfs->free.i) % lfs->block_count; - lfs->free.size = lfs_min(8*lfs->cfg->lookahead_size, lfs->free.ack); - lfs->free.i = 0; + // move lookahead buffer to the first unused block + // + // note we limit the lookahead buffer to at most the amount of blocks + // checkpointed, this prevents the math in lfs_alloc from underflowing + lfs->lookahead.start = (lfs->lookahead.start + lfs->lookahead.next) + % lfs->block_count; + lfs->lookahead.next = 0; + lfs->lookahead.size = lfs_min( + 8*lfs->cfg->lookahead_size, + lfs->lookahead.ckpoint); // find mask of free blocks from tree - memset(lfs->free.buffer, 0, lfs->cfg->lookahead_size); + memset(lfs->lookahead.buffer, 0, lfs->cfg->lookahead_size); int err = lfs_fs_rawtraverse(lfs, lfs_alloc_lookahead, lfs, true); if (err) { lfs_alloc_drop(lfs); @@ -645,35 +651,48 @@ static int lfs_fs_rawgc(lfs_t *lfs) { #ifndef LFS_READONLY static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) { while (true) { - while (lfs->free.i != lfs->free.size) { - lfs_block_t off = lfs->free.i; - lfs->free.i += 1; - lfs->free.ack -= 1; - - if (!(lfs->free.buffer[off / 32] & (1U << (off % 32)))) { + // scan our lookahead buffer for free blocks + while (lfs->lookahead.next < lfs->lookahead.size) { + if (!(lfs->lookahead.buffer[lfs->lookahead.next / 8] + & (1U << (lfs->lookahead.next % 8)))) { // found a free block - *block = (lfs->free.off + off) % lfs->block_count; - - // eagerly find next off so an alloc ack can - // discredit old lookahead blocks - while (lfs->free.i != lfs->free.size && - (lfs->free.buffer[lfs->free.i / 32] - & (1U << (lfs->free.i % 32)))) { - lfs->free.i += 1; - lfs->free.ack -= 1; + *block = (lfs->lookahead.start + lfs->lookahead.next) + % lfs->block_count; + + // eagerly find next free block to maximize how many blocks + // lfs_alloc_ckpoint makes available for scanning + while (true) { + lfs->lookahead.next += 1; + lfs->lookahead.ckpoint -= 1; + + if (lfs->lookahead.next >= lfs->lookahead.size + || !(lfs->lookahead.buffer[lfs->lookahead.next / 8] + & (1U << (lfs->lookahead.next % 8)))) { + return 0; + } } - - return 0; } + + lfs->lookahead.next += 1; + lfs->lookahead.ckpoint -= 1; } - // check if we have looked at all blocks since last ack - if (lfs->free.ack == 0) { - LFS_ERROR("No more free space %"PRIu32, - lfs->free.i + lfs->free.off); + // In order to keep our block allocator from spinning forever when our + // filesystem is full, we mark points where there are no in-flight + // allocations with a checkpoint before starting a set of allocations. + // + // If we've looked at all blocks since the last checkpoint, we report + // the filesystem as out of storage. + // + if (lfs->lookahead.ckpoint <= 0) { + LFS_ERROR("No more free space 0x%"PRIx32, + (lfs->lookahead.start + lfs->lookahead.next) + % lfs->cfg->block_count); return LFS_ERR_NOSPC; } + // No blocks in our lookahead buffer, we need to scan the filesystem for + // unused blocks in the next lookahead window. int err = lfs_fs_rawgc(lfs); if(err) { return err; @@ -2586,7 +2605,7 @@ static int lfs_rawmkdir(lfs_t *lfs, const char *path) { } // build up new directory - lfs_alloc_ack(lfs); + lfs_alloc_ckpoint(lfs); lfs_mdir_t dir; err = lfs_dir_alloc(lfs, &dir); if (err) { @@ -3272,7 +3291,7 @@ static int lfs_file_relocate(lfs_t *lfs, lfs_file_t *file) { #ifndef LFS_READONLY static int lfs_file_outline(lfs_t *lfs, lfs_file_t *file) { file->off = file->pos; - lfs_alloc_ack(lfs); + lfs_alloc_ckpoint(lfs); int err = lfs_file_relocate(lfs, file); if (err) { return err; @@ -3535,7 +3554,7 @@ static lfs_ssize_t lfs_file_flushedwrite(lfs_t *lfs, lfs_file_t *file, } // extend file with new blocks - lfs_alloc_ack(lfs); + lfs_alloc_ckpoint(lfs); int err = lfs_ctz_extend(lfs, &file->cache, &lfs->rcache, file->block, file->pos, &file->block, &file->off); @@ -3578,7 +3597,7 @@ static lfs_ssize_t lfs_file_flushedwrite(lfs_t *lfs, lfs_file_t *file, data += diff; nsize -= diff; - lfs_alloc_ack(lfs); + lfs_alloc_ckpoint(lfs); } return size; @@ -4180,15 +4199,14 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) { lfs_cache_zero(lfs, &lfs->rcache); lfs_cache_zero(lfs, &lfs->pcache); - // setup lookahead, must be multiple of 64-bits, 32-bit aligned + // setup lookahead buffer, note mount finishes initializing this after + // we establish a decent pseudo-random seed LFS_ASSERT(lfs->cfg->lookahead_size > 0); - LFS_ASSERT(lfs->cfg->lookahead_size % 8 == 0 && - (uintptr_t)lfs->cfg->lookahead_buffer % 4 == 0); if (lfs->cfg->lookahead_buffer) { - lfs->free.buffer = lfs->cfg->lookahead_buffer; + lfs->lookahead.buffer = lfs->cfg->lookahead_buffer; } else { - lfs->free.buffer = lfs_malloc(lfs->cfg->lookahead_size); - if (!lfs->free.buffer) { + lfs->lookahead.buffer = lfs_malloc(lfs->cfg->lookahead_size); + if (!lfs->lookahead.buffer) { err = LFS_ERR_NOMEM; goto cleanup; } @@ -4245,7 +4263,7 @@ static int lfs_deinit(lfs_t *lfs) { } if (!lfs->cfg->lookahead_buffer) { - lfs_free(lfs->free.buffer); + lfs_free(lfs->lookahead.buffer); } return 0; @@ -4265,12 +4283,12 @@ static int lfs_rawformat(lfs_t *lfs, const struct lfs_config *cfg) { LFS_ASSERT(cfg->block_count != 0); // create free lookahead - memset(lfs->free.buffer, 0, lfs->cfg->lookahead_size); - lfs->free.off = 0; - lfs->free.size = lfs_min(8*lfs->cfg->lookahead_size, + memset(lfs->lookahead.buffer, 0, lfs->cfg->lookahead_size); + lfs->lookahead.start = 0; + lfs->lookahead.size = lfs_min(8*lfs->cfg->lookahead_size, lfs->block_count); - lfs->free.i = 0; - lfs_alloc_ack(lfs); + lfs->lookahead.next = 0; + lfs_alloc_ckpoint(lfs); // create root dir lfs_mdir_t root; @@ -4478,7 +4496,7 @@ static int lfs_rawmount(lfs_t *lfs, const struct lfs_config *cfg) { // setup free lookahead, to distribute allocations uniformly across // boots, we start the allocator at a random location - lfs->free.off = lfs->seed % lfs->block_count; + lfs->lookahead.start = lfs->seed % lfs->block_count; lfs_alloc_drop(lfs); return 0; @@ -5451,10 +5469,10 @@ static int lfs1_mount(lfs_t *lfs, struct lfs1 *lfs1, lfs->lfs1->root[1] = LFS_BLOCK_NULL; // setup free lookahead - lfs->free.off = 0; - lfs->free.size = 0; - lfs->free.i = 0; - lfs_alloc_ack(lfs); + lfs->lookahead.start = 0; + lfs->lookahead.size = 0; + lfs->lookahead.next = 0; + lfs_alloc_ckpoint(lfs); // load superblock lfs1_dir_t dir; diff --git a/lfs.h b/lfs.h index 9eeab230..ad1da35a 100644 --- a/lfs.h +++ b/lfs.h @@ -226,7 +226,7 @@ struct lfs_config { // Size of the lookahead buffer in bytes. A larger lookahead buffer // increases the number of blocks found during an allocation pass. The // lookahead buffer is stored as a compact bitmap, so each byte of RAM - // can track 8 blocks. Must be a multiple of 8. + // can track 8 blocks. lfs_size_t lookahead_size; // Optional statically allocated read buffer. Must be cache_size. @@ -237,9 +237,8 @@ struct lfs_config { // By default lfs_malloc is used to allocate this buffer. void *prog_buffer; - // Optional statically allocated lookahead buffer. Must be lookahead_size - // and aligned to a 32-bit boundary. By default lfs_malloc is used to - // allocate this buffer. + // Optional statically allocated lookahead buffer. Must be lookahead_size. + // By default lfs_malloc is used to allocate this buffer. void *lookahead_buffer; // Optional upper limit on length of file names in bytes. No downside for @@ -430,13 +429,13 @@ typedef struct lfs { lfs_gstate_t gdisk; lfs_gstate_t gdelta; - struct lfs_free { - lfs_block_t off; + struct lfs_lookahead { + lfs_block_t start; lfs_block_t size; - lfs_block_t i; - lfs_block_t ack; - uint32_t *buffer; - } free; + lfs_block_t next; + lfs_block_t ckpoint; + uint8_t *buffer; + } lookahead; const struct lfs_config *cfg; lfs_size_t block_count; diff --git a/lfs_util.h b/lfs_util.h index 13e93961..8248d1d4 100644 --- a/lfs_util.h +++ b/lfs_util.h @@ -215,7 +215,9 @@ static inline uint32_t lfs_tobe32(uint32_t a) { uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size); // Allocate memory, only used if buffers are not provided to littlefs -// Note, memory must be 64-bit aligned +// +// littlefs current has no alignment requirements, as it only allocates +// byte-level buffers. static inline void *lfs_malloc(size_t size) { #ifndef LFS_NO_MALLOC return malloc(size); diff --git a/tests/test_orphans.toml b/tests/test_orphans.toml index 2c8405aa..d7040ed0 100644 --- a/tests/test_orphans.toml +++ b/tests/test_orphans.toml @@ -98,7 +98,7 @@ code = ''' lfs_mount(&lfs, cfg) => 0; // create an orphan lfs_mdir_t orphan; - lfs_alloc_ack(&lfs); + lfs_alloc_ckpoint(&lfs); lfs_dir_alloc(&lfs, &orphan) => 0; lfs_dir_commit(&lfs, &orphan, NULL, 0) => 0; @@ -170,7 +170,7 @@ code = ''' lfs_mount(&lfs, cfg) => 0; // create an orphan lfs_mdir_t orphan; - lfs_alloc_ack(&lfs); + lfs_alloc_ckpoint(&lfs); lfs_dir_alloc(&lfs, &orphan) => 0; lfs_dir_commit(&lfs, &orphan, NULL, 0) => 0;