Added benchmarks over mounting an unformatted disk

These locally show the expected O(d(n)) growth of the block_size search
when block_count is known.

A rough estimate of runtime for a 1 GiB device with a 90 MiB/s read bandwidth
(using the mt25q for rough numbers):

  known bs/bc       => ~1.44 us
  known block_size  => ~1.44 us
  known block_count => ~125 us
  unknown bs/bc     => ~376 ms

bd/lfs_emubd.c

@@ -220,7 +220,9 @@ int lfs_emubd_read(const struct lfs_config *cfg, lfs_block_t block,
     lfs_emubd_t *bd = cfg->context;
 
     // check if read is valid
-    LFS_ASSERT(block < bd->cfg->erase_count);
+    if (block >= bd->cfg->erase_count) {
+        return LFS_ERR_INVAL;
+    }
     LFS_ASSERT(off  % bd->cfg->read_size == 0);
     LFS_ASSERT(size % bd->cfg->read_size == 0);
     LFS_ASSERT(off+size <= bd->cfg->erase_size);

bd/lfs_filebd.c

@@ -70,7 +70,9 @@ int lfs_filebd_read(const struct lfs_config *cfg, lfs_block_t block,
     lfs_filebd_t *bd = cfg->context;
 
     // check if read is valid
-    LFS_ASSERT(block < bd->cfg->erase_count);
+    if (block >= bd->cfg->erase_count) {
+        return LFS_ERR_INVAL;
+    }
     LFS_ASSERT(off  % bd->cfg->read_size == 0);
     LFS_ASSERT(size % bd->cfg->read_size == 0);
     LFS_ASSERT(off+size <= bd->cfg->erase_size);

bd/lfs_rambd.c

@@ -60,7 +60,9 @@ int lfs_rambd_read(const struct lfs_config *cfg, lfs_block_t block,
     lfs_rambd_t *bd = cfg->context;
 
     // check if read is valid
-    LFS_ASSERT(block < bd->cfg->erase_count);
+    if (block >= bd->cfg->erase_count) {
+        return LFS_ERR_INVAL;
+    }
     LFS_ASSERT(off  % bd->cfg->read_size == 0);
     LFS_ASSERT(size % bd->cfg->read_size == 0);
     LFS_ASSERT(off+size <= bd->cfg->erase_size);

benches/bench_superblock.toml

@@ -1,4 +1,15 @@
-[cases.bench_superblocks_found]
+[cases.bench_superblocks_format]
+code = '''
+    lfs_t lfs;
+
+    BENCH_START();
+    lfs_format(&lfs, cfg) => 0;
+    BENCH_STOP();
+'''
+
+[cases.bench_superblocks_mount]
+defines.KNOWN_BLOCK_SIZE = [true, false]
+defines.KNOWN_BLOCK_COUNT = [true, false]
 # support benchmarking with files
 defines.N = [0, 1024]
 defines.FILE_SIZE = 8
@@ -28,6 +39,18 @@ code = '''
     }
     lfs_unmount(&lfs) => 0;
 
+    if (KNOWN_BLOCK_SIZE) {
+        cfg->block_size = BLOCK_SIZE;
+    } else {
+        cfg->block_size = 0;
+    }
+
+    if (KNOWN_BLOCK_COUNT) {
+        cfg->block_count = BLOCK_COUNT;
+    } else {
+        cfg->block_count = 0;
+    }
+
     BENCH_START();
     lfs_mount(&lfs, cfg) => 0;
     BENCH_STOP();
@@ -35,22 +58,27 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
-[cases.bench_superblocks_missing]
+[cases.bench_superblocks_mount_missing]
+defines.KNOWN_BLOCK_SIZE = [true, false]
+defines.KNOWN_BLOCK_COUNT = [true, false]
 code = '''
     lfs_t lfs;
 
+    if (KNOWN_BLOCK_SIZE) {
+        cfg->block_size = BLOCK_SIZE;
+    } else {
+        cfg->block_size = 0;
+    }
+
+    if (KNOWN_BLOCK_COUNT) {
+        cfg->block_count = BLOCK_COUNT;
+    } else {
+        cfg->block_count = 0;
+    }
+
     BENCH_START();
     int err = lfs_mount(&lfs, cfg);
     assert(err != 0);
     BENCH_STOP();
 '''
 
-[cases.bench_superblocks_format]
-code = '''
-    lfs_t lfs;
-
-    BENCH_START();
-    lfs_format(&lfs, cfg) => 0;
-    BENCH_STOP();
-'''
-