Reverted best-effort fsinfo.known_free/inuse prototype

See previous commit for motivation.

I can't think of how you could easily find this information from the
gbmap during/after mount, short of a O(d log_b d) scan through the
gbmap. Maybe useful, but probably not a great tradeoff for what is only
debug/diagnostic information.

So reverting, but maybe interesting to explore in the future with other
debug APIs.

Code changes:

                 code          stack          ctx
  before:       35220           2136          660
  after:        35160 (-0.2%)   2136 (+0.0%)  660 (+0.0%)

                 code          stack          ctx
  gbmap before: 38116           2152          776
  gbmap after:  38020 (-0.3%)   2152 (+0.0%)  772 (-0.5%)

lfs3.c

@@ -10459,8 +10459,6 @@ eot:;
 static void lfs3_gbmap_init(lfs3_gbmap_t *gbmap) {
     gbmap->window = 0;
     gbmap->known = 0;
-    // we lazily populate this during lookahead scans
-    gbmap->known_free = -1;
     lfs3_btree_init(&gbmap->b);
     lfs3_btree_init(&gbmap->b_p);
 }
@@ -16102,34 +16100,6 @@ int lfs3_fs_stat(lfs3_t *lfs3, struct lfs3_fsinfo *fsinfo) {
     fsinfo->name_limit = lfs3->name_limit;
     fsinfo->file_limit = lfs3->file_limit;
 
-    // return best effort knowledge of block usage
-
-    // if we have a gbmap, we choose whichever allocator has more
-    // information, otherwise we fall back to the lookahead buffer
-    if (LFS3_IFDEF_GBMAP(
-            lfs3_f_isgbmap(lfs3->flags)
-                // known_free=-1 indicates we don't know the free/inuse
-                // breakdown yet
-                && lfs3->gbmap.known_free != -1
-                && lfs3->gbmap.known >= lfs3->lookahead.known,
-            false)) {
-        #ifdef LFS3_GBMAP
-        fsinfo->known_free = lfs3->gbmap.known_free;
-        fsinfo->known_inuse = lfs3->gbmap.known - lfs3->gbmap.known_free;
-        #endif
-
-    } else {
-        lfs3_block_t free = 0;
-        for (lfs3_size_t i = 0; i < lfs3->lookahead.known; i++) {
-            if (!(lfs3->lookahead.buffer[(lfs3->lookahead.off+i) / 8]
-                    & (1 << ((lfs3->lookahead.off+i) % 8)))) {
-                free += 1;
-            }
-        }
-        fsinfo->known_free = free;
-        fsinfo->known_inuse = lfs3->lookahead.known - free;
-    }
-
     return 0;
 }
 

lfs3.h

@@ -687,16 +687,6 @@ struct lfs3_fsinfo {
 
     // Upper limit on the size of files in bytes.
     lfs3_off_t file_limit;
-
-    // Number of known free blocks
-    //
-    // Note this is limited by lookahead/gbmap
-    lfs3_block_t known_free;
-
-    // Number of known in-use blocks
-    //
-    // Note this is limited by lookahead/gbmap
-    lfs3_block_t known_inuse;
 };
 
 // Traversal info structure
@@ -1231,7 +1221,6 @@ typedef struct lfs3_grm {
 typedef struct lfs3_gbmap {
     lfs3_block_t window;
     lfs3_block_t known;
-    lfs3_sblock_t known_free;
     lfs3_btree_t b;
     lfs3_btree_t b_p;
 } lfs3_gbmap_t;
@@ -1287,7 +1276,7 @@ typedef struct lfs3 {
     struct lfs3_lookahead {
         lfs3_block_t window;
         lfs3_block_t off;
-        lfs3_size_t known;
+        lfs3_block_t known;
         lfs3_block_t ckpoint;
         uint8_t *buffer;
     } lookahead;