Added root entry and expanding superblocks

Expanding superblocks has been on my wishlist for a while. The basic
idea is that instead of maintaining a fixed offset blocks {0, 1} to the
the root directory (1 pointer), we maintain a dynamically sized
linked-list of superblocks that point to the actual root. If the number
of writes to the root exceeds some value, we increase the size of the
superblock linked-list.

This can leverage existing metadata-pair operations. The revision count for
metadata-pairs provides some knowledge on how much wear we've put on the
superblock, and the threaded linked-list can also be reused for this
purpose. This means superblock expansion is both optional and cheap to
implement.

Expanding superblocks helps both extremely small and extremely large filesystem
(extreme being relative of course). On the small end, we can actually
collapse the superblock into the root directory and drop the hard requirement
of 4-blocks for the superblock. On the large end, our superblock will
now last longer than the rest of the filesystem. Each time we expand,
the number of cycles until the superblock dies is increased by a power.

Before we were stuck with this layout:
level  cycles  limit    layout
1      E^2     390 MiB  s0 -> root

Now we expand every time a fixed offset is exceeded:
level  cycles  limit    layout
0      E       4 KiB    s0+root
1      E^2     390 MiB  s0 -> root
2      E^3     37 TiB   s0 -> s1 -> root
3      E^4     3.6 EiB  s0 -> s1 -> s2 -> root
...

Where the cycles are the number of cycles before death, and the limit is
the worst-case size a filesystem where early superblock death becomes a
concern (all writes to root using this formula: E^|s| = E*B, E = erase
cycles = 100000, B = block count, assuming 4096 byte blocks).

Note we can also store copies of the superblock entry on the expanded
superblocks. This may help filesystem recover tools in the future.

6 files changed, 146 insertions, 136 deletions

diff --git a/lfs.c b/lfs.c
index c7bcc04..ee8a7a8 100644
--- a/lfs.c
+++ b/lfs.c
@@ -377,6 +377,25 @@ static void lfs_ctz_tole32(struct lfs_ctz *ctz) {
     ctz->size = lfs_tole32(ctz->size);
 }
 
+static inline void lfs_superblock_fromle32(lfs_superblock_t *superblock) {
+    superblock->version     = lfs_fromle32(superblock->version);
+    superblock->block_size  = lfs_fromle32(superblock->block_size);
+    superblock->block_count = lfs_fromle32(superblock->block_count);
+    superblock->inline_max  = lfs_fromle32(superblock->inline_max);
+    superblock->attr_max    = lfs_fromle32(superblock->attr_max);
+    superblock->name_max    = lfs_fromle32(superblock->name_max);
+}
+
+static inline void lfs_superblock_tole32(lfs_superblock_t *superblock) {
+    superblock->version     = lfs_tole32(superblock->version);
+    superblock->block_size  = lfs_tole32(superblock->block_size);
+    superblock->block_count = lfs_tole32(superblock->block_count);
+    superblock->inline_max  = lfs_tole32(superblock->inline_max);
+    superblock->attr_max    = lfs_tole32(superblock->attr_max);
+    superblock->name_max    = lfs_tole32(superblock->name_max);
+}
+
+
 
 /// Entry tag operations ///
 #define LFS_MKTAG(type, id, size) \
@@ -524,15 +543,15 @@ static int lfs_commit_move(lfs_t *lfs, struct lfs_commit *commit,
 
 static int lfs_commit_attr(lfs_t *lfs, struct lfs_commit *commit,
         uint32_t tag, const void *buffer) {
-    if (lfs_tag_type(tag) == LFS_FROM_ATTRS) {
-        // special case for custom attributes
-        return lfs_commit_attrs(lfs, commit,
-                lfs_tag_id(tag), buffer);
-    } else if (lfs_tag_type(tag) == LFS_FROM_MOVE) {
+    if (lfs_tag_subtype(tag) == LFS_FROM_MOVE) {
         // special case for moves
         return lfs_commit_move(lfs, commit,
                 lfs_tag_size(tag), lfs_tag_id(tag),
                 buffer, NULL);
+    } else if (lfs_tag_subtype(tag) == LFS_FROM_ATTRS) {
+        // special case for custom attributes
+        return lfs_commit_attrs(lfs, commit,
+                lfs_tag_id(tag), buffer);
     }
 
     // check if we fit
@@ -628,7 +647,8 @@ static int lfs_commit_move(lfs_t *lfs, struct lfs_commit *commit,
             tag |= 0x80000000;
         }
 
-        if (lfs_tag_type(tag) == LFS_TYPE_DELETE && lfs_tag_id(tag) <= fromid) {
+        if (lfs_tag_type(tag) == LFS_TYPE_DELETE &&
+                lfs_tag_id(tag) <= fromid) {
             // something was deleted, we need to move around it
             fromid += 1;
         } else if (lfs_tag_id(tag) != fromid) {
@@ -667,8 +687,8 @@ static int lfs_commit_globals(lfs_t *lfs, struct lfs_commit *commit,
 
     lfs_global_xor(locals, &lfs->locals);
     int err = lfs_commit_attr(lfs, commit,
-            LFS_MKTAG(LFS_TYPE_GLOBALS + locals->s.deorphaned,
-                0x3ff, sizeof(lfs_global_t)), locals);
+            LFS_MKTAG(LFS_TYPE_GLOBALS + locals->s.deorphaned, 0x3ff, 10),
+            locals);
     lfs_global_xor(locals, &lfs->locals);
     return err;
 }
@@ -726,7 +746,7 @@ static int lfs_commit_crc(lfs_t *lfs, struct lfs_commit *commit) {
 
 // internal dir operations
 static int lfs_dir_alloc(lfs_t *lfs, lfs_mdir_t *dir) {
-    // allocate pair of dir blocks (backwards, so we write to block 1 first)
+    // allocate pair of dir blocks (backwards, so we write block 1 first)
     for (int i = 0; i < 2; i++) {
         int err = lfs_alloc(lfs, &dir->pair[(i+1)%2]);
         if (err) {
@@ -756,10 +776,9 @@ static int lfs_dir_alloc(lfs_t *lfs, lfs_mdir_t *dir) {
     return 0;
 }
 
-static int32_t lfs_dir_find(lfs_t *lfs,
+static int32_t lfs_dir_fetchmatch(lfs_t *lfs,
         lfs_mdir_t *dir, const lfs_block_t pair[2],
-        uint32_t findmask, uint32_t findtag,
-        const void *findbuffer) {
+        uint32_t findmask, uint32_t findtag, const void *findbuffer) {
     dir->pair[0] = pair[0];
     dir->pair[1] = pair[1];
     int32_t foundtag = LFS_ERR_NOENT;
@@ -887,7 +906,7 @@ static int32_t lfs_dir_find(lfs_t *lfs,
                 } else if (lfs_tag_subtype(tag) == LFS_TYPE_GLOBALS) {
                     templocals.s.deorphaned = (lfs_tag_type(tag) & 1);
                     err = lfs_bd_read(lfs, dir->pair[0], off+sizeof(tag),
-                            &templocals, sizeof(templocals));
+                            &templocals, 10);
                     if (err) {
                         if (err == LFS_ERR_CORRUPT) {
                             dir->erased = false;
@@ -906,7 +925,7 @@ static int32_t lfs_dir_find(lfs_t *lfs,
                     }
                 } else if ((tag & findmask) == (findtag & findmask)) {
                     int res = lfs_bd_cmp(lfs, dir->pair[0], off+sizeof(tag),
-                            findbuffer, lfs_tag_size(tag));
+                            findbuffer, lfs_tag_size(findtag));
                     if (res < 0) {
                         if (res == LFS_ERR_CORRUPT) {
                             dir->erased = false;
@@ -953,7 +972,8 @@ static int32_t lfs_dir_find(lfs_t *lfs,
 
 static int lfs_dir_fetch(lfs_t *lfs,
         lfs_mdir_t *dir, const lfs_block_t pair[2]) {
-    int32_t res = lfs_dir_find(lfs, dir, pair, 0xffffffff, 0xffffffff, NULL);
+    int32_t res = lfs_dir_fetchmatch(lfs, dir, pair,
+            0xffffffff, 0xffffffff, NULL);
     if (res < 0 && res != LFS_ERR_NOENT) {
         return res;
     }
@@ -961,6 +981,23 @@ static int lfs_dir_fetch(lfs_t *lfs,
     return 0;
 }
 
+static int32_t lfs_dir_find(lfs_t *lfs,
+        lfs_mdir_t *dir, const lfs_block_t pair[2], bool fs,
+        uint32_t findmask, uint32_t findtag, const void *findbuffer) {
+    dir->split = true;
+    dir->tail[0] = pair[0];
+    dir->tail[1] = pair[1];
+    while ((dir->split || fs) && !lfs_pair_isnull(dir->tail)) {
+        int32_t tag = lfs_dir_fetchmatch(lfs, dir, dir->tail,
+                findmask, findtag, findbuffer);
+        if (tag != LFS_ERR_NOENT) {
+            return tag;
+        }
+    }
+
+    return LFS_ERR_NOENT;
+}
+
 static int32_t lfs_dir_get(lfs_t *lfs, lfs_mdir_t *dir,
         uint32_t getmask, uint32_t gettag, void *buffer) {
     int32_t getdiff = 0;
@@ -979,6 +1016,8 @@ static int lfs_dir_compact(lfs_t *lfs,
         lfs_mdir_t *source, uint16_t begin, uint16_t end) {
     // save some state in case block is bad
     const lfs_block_t oldpair[2] = {dir->pair[1], dir->pair[0]};
+    int16_t ack;
+    bool expanding = false;
     bool relocated = false;
 
     // There's nothing special about our global delta, so feed it back
@@ -989,9 +1028,25 @@ static int lfs_dir_compact(lfs_t *lfs,
     // increment revision count
     dir->rev += 1;
 
+    if (lfs_pair_cmp(dir->pair, (const lfs_block_t[2]){0, 1}) == 0 &&
+            dir->rev % 16 == 0) {
+        // we're writing too much to the superblock, should we expand?
+        lfs_ssize_t res = lfs_fs_size(lfs);
+        if (res < 0) {
+            return res;
+        }
+
+        // do we have enough space to expand?
+        if (res < lfs->cfg->block_count/2) {
+            expanding = (lfs_pair_cmp(dir->pair, lfs->root) != 0);
+            ack = 0;
+            goto split;
+        }
+    }
+
     while (true) {
         // last complete id
-        int16_t ack = -1;
+        ack = -1;
         dir->count = end - begin;
 
         if (true) {
@@ -1111,7 +1166,7 @@ split:
         tail.tail[0] = dir->tail[0];
         tail.tail[1] = dir->tail[1];
 
-        err = lfs_dir_compact(lfs, &tail, attrs, dir, ack+1, end);
+        err = lfs_dir_compact(lfs, &tail, attrs, dir, ack+1-expanding, end);
         if (err) {
             return err;
         }
@@ -1390,25 +1445,10 @@ nextname:
         }
 
         // find entry matching name
-        while (true) {
-            tag = lfs_dir_find(lfs, dir, pair, 0x7c000fff,
-                    LFS_MKTAG(LFS_TYPE_NAME, 0, namelen), name);
-            if (tag < 0 && tag != LFS_ERR_NOENT) {
-                return tag;
-            }
-
-            if (tag != LFS_ERR_NOENT) {
-                // found it
-                break;
-            }
-
-            if (!dir->split) {
-                // couldn't find it
-                return LFS_ERR_NOENT;
-            }
-
-            pair[0] = dir->tail[0];
-            pair[1] = dir->tail[1];
+        tag = lfs_dir_find(lfs, dir, pair, false, 0x7c000fff,
+                LFS_MKTAG(LFS_TYPE_NAME, 0, namelen), name);
+        if (tag < 0) {
+            return tag;
         }
 
         // to next name
@@ -2721,24 +2761,6 @@ int lfs_setattr(lfs_t *lfs, const char *path,
 
 
 /// Filesystem operations ///
-static inline void lfs_superblockfromle32(lfs_superblock_t *superblock) {
-    superblock->version     = lfs_fromle32(superblock->version);
-    superblock->block_size  = lfs_fromle32(superblock->block_size);
-    superblock->block_count = lfs_fromle32(superblock->block_count);
-    superblock->inline_max  = lfs_fromle32(superblock->inline_max);
-    superblock->attr_max    = lfs_fromle32(superblock->attr_max);
-    superblock->name_max    = lfs_fromle32(superblock->name_max);
-}
-
-static inline void lfs_superblocktole32(lfs_superblock_t *superblock) {
-    superblock->version     = lfs_tole32(superblock->version);
-    superblock->block_size  = lfs_tole32(superblock->block_size);
-    superblock->block_count = lfs_tole32(superblock->block_count);
-    superblock->inline_max  = lfs_tole32(superblock->inline_max);
-    superblock->attr_max    = lfs_tole32(superblock->attr_max);
-    superblock->name_max    = lfs_tole32(superblock->name_max);
-}
-
 static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     lfs->cfg = cfg;
     int err = 0;
@@ -2859,30 +2881,13 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
     lfs->free.i = 0;
     lfs_alloc_ack(lfs);
 
-    // create superblock dir
-    lfs_mdir_t dir;
-    err = lfs_dir_alloc(lfs, &dir);
-    if (err) {
-        goto cleanup;
-    }
-
-    // write root directory
+    // create root dir
     lfs_mdir_t root;
     err = lfs_dir_alloc(lfs, &root);
     if (err) {
         goto cleanup;
     }
 
-    err = lfs_dir_commit(lfs, &root, NULL);
-    if (err) {
-        goto cleanup;
-    }
-
-    lfs->root[0] = root.pair[0];
-    lfs->root[1] = root.pair[1];
-    dir.tail[0] = lfs->root[0];
-    dir.tail[1] = lfs->root[1];
-
     // write one superblock
     lfs_superblock_t superblock = {
         .magic = {"littlefs"},
@@ -2895,20 +2900,17 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
         .inline_max  = lfs->inline_max,
     };
 
-    lfs_superblocktole32(&superblock);
-    lfs_pair_tole32(lfs->root);
-    err = lfs_dir_commit(lfs, &dir,
+    lfs_superblock_tole32(&superblock);
+    err = lfs_dir_commit(lfs, &root,
             LFS_MKATTR(LFS_TYPE_SUPERBLOCK, 0, &superblock, sizeof(superblock),
-            LFS_MKATTR(LFS_TYPE_DIRSTRUCT, 0, lfs->root, sizeof(lfs->root),
+            LFS_MKATTR(LFS_TYPE_ROOT, 1, NULL, 0,
             NULL)));
-    lfs_pair_fromle32(lfs->root);
-    lfs_superblockfromle32(&superblock);
     if (err) {
         goto cleanup;
     }
 
     // sanity check that fetch works
-    err = lfs_dir_fetch(lfs, &dir, (const lfs_block_t[2]){0, 1});
+    err = lfs_dir_fetch(lfs, &root, (const lfs_block_t[2]){0, 1});
     if (err) {
         goto cleanup;
     }
@@ -2931,27 +2933,34 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     lfs_alloc_ack(lfs);
 
     // load superblock
-    lfs_mdir_t superdir;
-    err = lfs_dir_fetch(lfs, &superdir, (const lfs_block_t[2]){0, 1});
+    lfs_mdir_t root;
+    err = lfs_dir_fetch(lfs, &root, (const lfs_block_t[2]){0, 1});
     if (err) {
-        goto cleanup;
+        return err;
     }
 
     lfs_superblock_t superblock;
-    int32_t res = lfs_dir_get(lfs, &superdir, 0x7ffff000,
+    int32_t res = lfs_dir_get(lfs, &root, 0x7fc00000,
             LFS_MKTAG(LFS_TYPE_SUPERBLOCK, 0, sizeof(superblock)),
             &superblock);
     if (res < 0) {
         err = res;
         goto cleanup;
     }
-    lfs_superblockfromle32(&superblock);
+    lfs_superblock_fromle32(&superblock);
 
-    if (memcmp(superblock.magic, "littlefs", 8) != 0) {
-        LFS_ERROR("Invalid superblock \"%.8s\"", superblock.magic);
-        return LFS_ERR_INVAL;
+    // find root
+    int32_t tag = lfs_dir_find(lfs,
+            &root, (const lfs_block_t[2]){0, 1}, false, 0x7fc00000,
+            LFS_MKTAG(LFS_TYPE_ROOT, 0, 0), NULL);
+    if (tag < 0) {
+        return tag;
     }
 
+    lfs->root[0] = root.pair[0];
+    lfs->root[1] = root.pair[1];
+
+    // check version
     uint16_t major_version = (0xffff & (superblock.version >> 16));
     uint16_t minor_version = (0xffff & (superblock.version >>  0));
     if ((major_version != LFS_DISK_VERSION_MAJOR ||
@@ -2962,15 +2971,6 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
         goto cleanup;
     }
 
-    res = lfs_dir_get(lfs, &superdir, 0x7ffff000,
-            LFS_MKTAG(LFS_TYPE_DIRSTRUCT, 0, sizeof(lfs->root)),
-            &lfs->root);
-    if (res < 0) {
-        err = res;
-        goto cleanup;
-    }
-    lfs_pair_fromle32(lfs->root);
-
     // check superblock configuration
     if (superblock.attr_max) {
         if (superblock.attr_max > lfs->attr_max) {
@@ -3145,16 +3145,11 @@ static int32_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t pair[2],
     lfs_block_t child[2] = {pair[0], pair[1]};
     lfs_pair_tole32(child);
     for (int i = 0; i < 2; i++) {
-        // iterate over all directory directory entries
-        parent->tail[0] = 0;
-        parent->tail[1] = 1;
-        while (!lfs_pair_isnull(parent->tail)) {
-            int32_t tag = lfs_dir_find(lfs, parent, parent->tail, 0x7fc00fff,
-                    LFS_MKTAG(LFS_TYPE_DIRSTRUCT, 0, sizeof(child)),
-                    child);
-            if (tag != LFS_ERR_NOENT) {
-                return tag;
-            }
+        int32_t tag = lfs_dir_find(lfs, parent,
+                (const lfs_block_t[2]){0, 1}, true, 0x7fc00fff,
+                LFS_MKTAG(LFS_TYPE_DIRSTRUCT, 0, sizeof(child)), child);
+        if (tag != LFS_ERR_NOENT) {
+            return tag;
         }
 
         lfs_pair_swap(child);
@@ -3190,6 +3185,7 @@ static int lfs_fs_relocate(lfs_t *lfs,
 
     if (tag != LFS_ERR_NOENT) {
         // update disk, this creates a desync
+        lfs_global_deorphaned(lfs, false);
         lfs_pair_tole32(newpair);
         int err = lfs_dir_commit(lfs, &parent,
                 &(lfs_mattr_t){.tag=tag, .buffer=newpair});
diff --git a/lfs.h b/lfs.h
index 4ced50a..df0927e 100644
--- a/lfs.h
+++ b/lfs.h
@@ -93,7 +93,8 @@ enum lfs_type {
 
     // internally used types
     LFS_TYPE_USER           = 0x100,
-    LFS_TYPE_SUPERBLOCK     = 0x010,
+    LFS_TYPE_SUPERBLOCK     = 0x011,
+    LFS_TYPE_ROOT           = 0x012,
     LFS_TYPE_NAME           = 0x000,
     LFS_TYPE_DELETE         = 0x030,
     LFS_TYPE_STRUCT         = 0x040,
@@ -110,8 +111,9 @@ enum lfs_type {
     // internal chip sources
     LFS_FROM_REGION         = 0x000,
     LFS_FROM_DISK           = 0x200,
-    LFS_FROM_MOVE           = 0x021,
-    LFS_FROM_ATTRS          = 0x022,
+    LFS_FROM_MOVE           = 0x050,
+    LFS_FROM_ATTRS          = 0x060,
+    LFS_FROM_SUPERBLOCK     = 0x070,
 };
 
 // File open flags
diff --git a/tests/test_alloc.sh b/tests/test_alloc.sh
index d3c8da4..2be8e17 100755
--- a/tests/test_alloc.sh
+++ b/tests/test_alloc.sh
@@ -206,7 +206,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < (cfg.block_count-6)*(cfg.block_size-8);
+            i < (cfg.block_count-4)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -286,7 +286,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < (cfg.block_count-6)*(cfg.block_size-8);
+            i < (cfg.block_count-4)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -320,7 +320,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -331,7 +331,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -349,7 +349,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -363,7 +363,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -383,7 +383,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -394,7 +394,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i < ((cfg.block_count-2+1)/2)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
@@ -412,7 +412,7 @@ tests/test.py << TEST
     size = strlen("blahblahblahblah");
     memcpy(buffer, "blahblahblahblah", size);
     for (lfs_size_t i = 0;
-            i < ((cfg.block_count-4)/2 - 1)*(cfg.block_size-8);
+            i < ((cfg.block_count-2)/2 - 1)*(cfg.block_size-8);
             i += size) {
         lfs_file_write(&lfs, &file[0], buffer, size) => size;
     }
diff --git a/tests/test_format.sh b/tests/test_format.sh
index cff0bac..06438bc 100755
--- a/tests/test_format.sh
+++ b/tests/test_format.sh
@@ -9,6 +9,15 @@ tests/test.py << TEST
     lfs_format(&lfs, &cfg) => 0;
 TEST
 
+echo "--- Basic mounting ---"
+tests/test.py << TEST
+    lfs_format(&lfs, &cfg) => 0;
+TEST
+tests/test.py << TEST
+    lfs_mount(&lfs, &cfg) => 0;
+    lfs_unmount(&lfs) => 0;
+TEST
+
 echo "--- Invalid superblocks ---"
 ln -f -s /dev/zero blocks/0
 ln -f -s /dev/zero blocks/1
@@ -17,22 +26,25 @@ tests/test.py << TEST
 TEST
 rm blocks/0 blocks/1
 
-echo "--- Basic mounting ---"
-tests/test.py << TEST
-    lfs_format(&lfs, &cfg) => 0;
-TEST
+echo "--- Invalid mount ---"
 tests/test.py << TEST
-    lfs_mount(&lfs, &cfg) => 0;
-    lfs_unmount(&lfs) => 0;
+    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
 TEST
 
-echo "--- Invalid mount ---"
+echo "--- Expanding superblock ---"
 tests/test.py << TEST
     lfs_format(&lfs, &cfg) => 0;
+    lfs_mount(&lfs, &cfg) => 0;
+    for (int i = 0; i < 100; i++) {
+        lfs_mkdir(&lfs, "dummy") => 0;
+        lfs_remove(&lfs, "dummy") => 0;
+    }
+    lfs_unmount(&lfs) => 0;
 TEST
-rm -f blocks/0 blocks/1
 tests/test.py << TEST
-    lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
+    lfs_mount(&lfs, &cfg) => 0;
+    lfs_mkdir(&lfs, "dummy") => 0;
+    lfs_unmount(&lfs) => 0;
 TEST
 
 echo "--- Results ---"
diff --git a/tests/test_move.sh b/tests/test_move.sh
index a36d058..824d4d3 100755
--- a/tests/test_move.sh
+++ b/tests/test_move.sh
@@ -59,7 +59,7 @@ tests/test.py << TEST
     lfs_rename(&lfs, "b/hello", "c/hello") => 0;
     lfs_unmount(&lfs) => 0;
 TEST
-tests/corrupt.py blocks/{6,7}
+tests/corrupt.py blocks/{4,5}
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_dir_open(&lfs, &dir[0], "b") => 0;
@@ -86,8 +86,8 @@ tests/test.py << TEST
     lfs_rename(&lfs, "c/hello", "d/hello") => 0;
     lfs_unmount(&lfs) => 0;
 TEST
+tests/corrupt.py blocks/{6,7}
 tests/corrupt.py blocks/{8,9}
-tests/corrupt.py blocks/{a,b}
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_dir_open(&lfs, &dir[0], "c") => 0;
@@ -166,7 +166,7 @@ tests/test.py << TEST
     lfs_rename(&lfs, "b/hi", "c/hi") => 0;
     lfs_unmount(&lfs) => 0;
 TEST
-tests/corrupt.py blocks/{6,7}
+tests/corrupt.py blocks/{4,5}
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_dir_open(&lfs, &dir[0], "b") => 0;
@@ -193,8 +193,8 @@ tests/test.py << TEST
     lfs_rename(&lfs, "c/hi", "d/hi") => 0;
     lfs_unmount(&lfs) => 0;
 TEST
+tests/corrupt.py blocks/{6,7}
 tests/corrupt.py blocks/{8,9}
-tests/corrupt.py blocks/{a,b}
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_dir_open(&lfs, &dir[0], "c") => 0;
diff --git a/tests/test_orphan.sh b/tests/test_orphan.sh
index 6aa36d9..e66e592 100755
--- a/tests/test_orphan.sh
+++ b/tests/test_orphan.sh
@@ -17,26 +17,26 @@ tests/test.py << TEST
 TEST
 # corrupt most recent commit, this should be the update to the previous
 # linked-list entry and should orphan the child
-tests/corrupt.py blocks/{8,9}
-tests/test.py  << TEST
+tests/corrupt.py blocks/{6,7}
+tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
 
     lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
     lfs_ssize_t before = lfs_fs_size(&lfs);
-    before => 10;
+    before => 8;
 
     lfs_unmount(&lfs) => 0;
     lfs_mount(&lfs, &cfg) => 0;
 
     lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
     lfs_ssize_t orphaned = lfs_fs_size(&lfs);
-    orphaned => 10;
+    orphaned => 8;
 
     lfs_mkdir(&lfs, "parent/otherchild") => 0;
 
     lfs_stat(&lfs, "parent/orphan", &info) => LFS_ERR_NOENT;
     lfs_ssize_t deorphaned = lfs_fs_size(&lfs);
-    deorphaned => 10;
+    deorphaned => 8;
 
     lfs_unmount(&lfs) => 0;
 TEST