Renamed a number of internal block-allocator fields

- Renamed lfs.free      -> lfs.lookahead
- Renamed lfs.free.off  -> lfs.lookahead.start
- Renamed lfs.free.i    -> lfs.lookahead.next
- Renamed lfs.free.ack  -> lfs.lookahead.ckpoint
- Renamed lfs_alloc_ack -> lfs_alloc_ckpoint

These have been named a bit confusingly, and I think the new names make
their relevant purposes a bit clearer.

At the very it's clear lfs.lookahead is related to the lookahead buffer.
(and doesn't imply a closed free-bitmap).

lfs.c

@@ -596,11 +596,11 @@ 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 / 32] |= 1U << (off % 32);
     }
 
     return 0;
@@ -610,28 +610,31 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
 // 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;
+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 free offset at the first unused block (lfs->lookahead.next)
+    // lfs->lookahead.next is equal lfs->lookahead.size when all blocks are used
+    lfs->lookahead.start = (lfs->lookahead.start + lfs->lookahead.next) 
+            % lfs->block_count;
+    lfs->lookahead.size = lfs_min(
+            8*lfs->cfg->lookahead_size,
+            lfs->lookahead.ckpoint);
+    lfs->lookahead.next = 0;
 
     // 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);
@@ -645,22 +648,22 @@ 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;
+        while (lfs->lookahead.next != lfs->lookahead.size) {
+            lfs_block_t off = lfs->lookahead.next;
+            lfs->lookahead.next += 1;
+            lfs->lookahead.ckpoint -= 1;
 
-            if (!(lfs->free.buffer[off / 32] & (1U << (off % 32)))) {
+            if (!(lfs->lookahead.buffer[off / 32] & (1U << (off % 32)))) {
                 // found a free block
-                *block = (lfs->free.off + off) % lfs->block_count;
+                *block = (lfs->lookahead.start + 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;
+                while (lfs->lookahead.next != lfs->lookahead.size &&
+                        (lfs->lookahead.buffer[lfs->lookahead.next / 32]
+                            & (1U << (lfs->lookahead.next % 32)))) {
+                    lfs->lookahead.next += 1;
+                    lfs->lookahead.ckpoint -= 1;
                 }
 
                 return 0;
@@ -668,9 +671,9 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
         }
 
         // check if we have looked at all blocks since last ack
-        if (lfs->free.ack == 0) {
+        if (lfs->lookahead.ckpoint == 0) {
             LFS_ERROR("No more free space %"PRIu32,
-                    lfs->free.i + lfs->free.off);
+                    lfs->lookahead.next + lfs->lookahead.start);
             return LFS_ERR_NOSPC;
         }
 
@@ -2586,7 +2589,7 @@ 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 +3275,7 @@ relocate:
 #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 +3538,7 @@ 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 +3581,7 @@ relocate:
         data += diff;
         nsize -= diff;
 
-        lfs_alloc_ack(lfs);
+        lfs_alloc_ckpoint(lfs);
     }
 
     return size;
@@ -4185,10 +4188,10 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     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 +4248,7 @@ 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 +4268,12 @@ 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 +4481,7 @@ 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 +5454,10 @@ 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;

lfs.h

@@ -430,13 +430,13 @@ 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;
+        lfs_block_t next;
+        lfs_block_t ckpoint;
         uint32_t *buffer;
-    } free;
+    } lookahead;
 
     const struct lfs_config *cfg;
     lfs_size_t block_count;

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;