paths: Changed CREAT with a trailing slash to return NOTDIR

- before: lfs_file_open("missing/") => LFS_ERR_ISDIR
- after:  lfs_file_open("missing/") => LFS_ERR_NOTDIR

As noted by bmcdonnell-fb, returning LFS_ERR_ISDIR here was inconsistent
with the case where the file exists:

  case                           before          after
  lfs_file_open("dir_a")      => LFS_ERR_ISDIR   LFS_ERR_ISDIR
  lfs_file_open("dir_a/")     => LFS_ERR_ISDIR   LFS_ERR_ISDIR
  lfs_file_open("reg_a/")     => LFS_ERR_NOTDIR  LFS_ERR_NOTDIR
  lfs_file_open("missing_a/") => LFS_ERR_ISDIR   LFS_ERR_NOTDIR

Note this is consistent with the behavior of lfs_stat:

  lfs_file_open("reg_a/") => LFS_ERR_NOTDIR
  lfs_stat("reg_a/")      => LFS_ERR_NOTDIR

And the only other function that can "create" files, lfs_rename:

  lfs_file_open("missing_a/")       => LFS_ERR_NOTDIR
  lfs_rename("reg_a", "missing_a/") => LFS_ERR_NOTDIR

There is some ongoing discussion about if these should return NOTDIR,
ISDIR, or INVAL, but this is at least an improvement over the
rename/open mismatch.

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
       github.event.workflow_run.head_sha == github.sha}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           ref: ${{github.event.workflow_run.head_sha}}
           # need workflow access since we push branches
@@ -30,26 +30,29 @@ jobs:
           fetch-depth: 0
 
       # try to get results from tests
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: actions/download-artifact@v4
         continue-on-error: true
         with:
-          workflow: ${{github.event.workflow_run.name}}
-          run_id: ${{github.event.workflow_run.id}}
-          name: sizes
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          run-id: ${{github.event.workflow_run.id}}
+          pattern: '{sizes,sizes-*}'
+          merge-multiple: true
           path: sizes
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: actions/download-artifact@v4
         continue-on-error: true
         with:
-          workflow: ${{github.event.workflow_run.name}}
-          run_id: ${{github.event.workflow_run.id}}
-          name: cov
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          run-id: ${{github.event.workflow_run.id}}
+          pattern: '{cov,cov-*}'
+          merge-multiple: true
           path: cov
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: actions/download-artifact@v4
         continue-on-error: true
         with:
-          workflow: ${{github.event.workflow_run.name}}
-          run_id: ${{github.event.workflow_run.id}}
-          name: bench
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          run-id: ${{github.event.workflow_run.id}}
+          pattern: '{bench,bench-*}'
+          merge-multiple: true
           path: bench
 
       - name: find-version

.github/workflows/status.yml

@@ -13,12 +13,13 @@ jobs:
   status:
     runs-on: ubuntu-latest
     steps:
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: actions/download-artifact@v4
         continue-on-error: true
         with:
-          workflow: ${{github.event.workflow_run.name}}
-          run_id: ${{github.event.workflow_run.id}}
-          name: status
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          run-id: ${{github.event.workflow_run.id}}
+          pattern: '{status,status-*}'
+          merge-multiple: true
           path: status
       - name: update-status
         continue-on-error: true
@@ -67,12 +68,13 @@ jobs:
 
     steps:
       # generated comment?
-      - uses: dawidd6/action-download-artifact@v2
+      - uses: actions/download-artifact@v4
         continue-on-error: true
         with:
-          workflow: ${{github.event.workflow_run.name}}
-          run_id: ${{github.event.workflow_run.id}}
-          name: comment
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          run-id: ${{github.event.workflow_run.id}}
+          pattern: '{comment,comment-*}'
+          merge-multiple: true
           path: comment
       - name: update-comment
         continue-on-error: true

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
         arch: [x86_64, thumb, mips, powerpc]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -235,9 +235,9 @@ jobs:
 
       # create size statuses
       - name: upload-sizes
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
-          name: sizes
+          name: sizes-${{matrix.arch}}
           path: sizes
       - name: status-sizes
         run: |
@@ -273,16 +273,17 @@ jobs:
             }' | tee status/$(basename $f .csv).json
           done
       - name: upload-status-sizes
-        uses: actions/upload-artifact@v2
+        if: ${{matrix.arch == 'x86_64'}}
+        uses: actions/upload-artifact@v4
         with:
-          name: status
+          name: status-sizes-${{matrix.arch}}
           path: status
           retention-days: 1
 
       # create cov statuses
       - name: upload-cov
         if: ${{matrix.arch == 'x86_64'}}
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: cov
           path: cov
@@ -317,11 +318,11 @@ jobs:
               target_step: env.STEP,
             }' | tee status/$(basename $f .csv)-$s.json
           done
-      - name: upload-status-sizes
+      - name: upload-status-cov
         if: ${{matrix.arch == 'x86_64'}}
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
-          name: status
+          name: status-cov
           path: status
           retention-days: 1
 
@@ -336,7 +337,7 @@ jobs:
         pls: [1, 2]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -361,7 +362,7 @@ jobs:
   test-no-intrinsics:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -378,7 +379,7 @@ jobs:
   test-multiversion:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -395,7 +396,7 @@ jobs:
   test-lfs2_0:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -414,7 +415,7 @@ jobs:
   test-valgrind:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -436,7 +437,7 @@ jobs:
   test-clang:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -459,7 +460,7 @@ jobs:
   bench:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -491,7 +492,7 @@ jobs:
 
       # create bench statuses
       - name: upload-bench
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: bench
           path: bench
@@ -525,9 +526,9 @@ jobs:
             }' | tee status/$(basename $f .csv)-$s.json
           done
       - name: upload-status-bench
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
-          name: status
+          name: status-bench
           path: status
           retention-days: 1
 
@@ -535,10 +536,10 @@ jobs:
   test-compat:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         if: ${{github.event_name == 'pull_request'}}
       # checkout the current pr target into lfsp
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         if: ${{github.event_name == 'pull_request'}}
         with:
           ref: ${{github.event.pull_request.base.ref}}
@@ -572,7 +573,7 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{!endsWith(github.ref, '-prefix')}}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -582,7 +583,7 @@ jobs:
           gcc --version
           python3 --version
           fusermount -V
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           repository: littlefs-project/littlefs-fuse
           ref: v2
@@ -622,7 +623,7 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{!endsWith(github.ref, '-prefix')}}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: install
         run: |
           # need a few things
@@ -632,12 +633,12 @@ jobs:
           gcc --version
           python3 --version
           fusermount -V
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           repository: littlefs-project/littlefs-fuse
           ref: v2
           path: v2
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           repository: littlefs-project/littlefs-fuse
           ref: v1
@@ -694,7 +695,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [test, bench]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         if: ${{github.event_name == 'pull_request'}}
       - name: install
         if: ${{github.event_name == 'pull_request'}}
@@ -704,23 +705,26 @@ jobs:
           pip3 install toml
           gcc --version
           python3 --version
-      - uses: actions/download-artifact@v2
+      - uses: actions/download-artifact@v4
         if: ${{github.event_name == 'pull_request'}}
         continue-on-error: true
         with:
-          name: sizes
+          pattern: '{sizes,sizes-*}'
+          merge-multiple: true
           path: sizes
-      - uses: actions/download-artifact@v2
+      - uses: actions/download-artifact@v4
         if: ${{github.event_name == 'pull_request'}}
         continue-on-error: true
         with:
-          name: cov
+          pattern: '{cov,cov-*}'
+          merge-multiple: true
           path: cov
-      - uses: actions/download-artifact@v2
+      - uses: actions/download-artifact@v4
         if: ${{github.event_name == 'pull_request'}}
         continue-on-error: true
         with:
-          name: bench
+          pattern: '{bench,bench-*}'
+          merge-multiple: true
           path: bench
 
       # try to find results from tests
@@ -862,7 +866,7 @@ jobs:
             body: $comment,
           }' | tee comment/comment.json
       - name: upload-comment
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: comment
           path: comment

SPEC.md

@@ -441,9 +441,10 @@ Superblock fields:
 
 7. **Attr max (32-bits)** - Maximum size of file attributes in bytes.
 
-The superblock must always be the first entry (id 0) in a metadata pair as well
-as be the first entry written to the block. This means that the superblock
-entry can be read from a device using offsets alone.
+The superblock must always be the first entry (id 0) in the metadata pair, and
+the name tag must always be the first tag in the metadata pair. This makes it
+so that the magic string "littlefs" will always reside at offset=8 in a valid
+littlefs superblock.
 
 ---
 #### `0x2xx` LFS_TYPE_STRUCT

lfs.c

@@ -282,6 +282,21 @@ static int lfs_bd_erase(lfs_t *lfs, lfs_block_t block) {
 
 
 /// Small type-level utilities ///
+
+// some operations on paths
+static inline lfs_size_t lfs_path_namelen(const char *path) {
+    return strcspn(path, "/");
+}
+
+static inline bool lfs_path_islast(const char *path) {
+    lfs_size_t namelen = lfs_path_namelen(path);
+    return path[namelen + strspn(path + namelen, "/")] == '\0';
+}
+
+static inline bool lfs_path_isdir(const char *path) {
+    return path[lfs_path_namelen(path)] != '\0';
+}
+
 // operations on block pairs
 static inline void lfs_pair_swap(lfs_block_t pair[2]) {
     lfs_block_t t = pair[0];
@@ -1461,32 +1476,46 @@ static int lfs_dir_find_match(void *data,
     return LFS_CMP_EQ;
 }
 
+// lfs_dir_find tries to set path and id even if file is not found
+//
+// returns:
+// - 0                  if file is found
+// - LFS_ERR_NOENT      if file or parent is not found
+// - LFS_ERR_NOTDIR     if parent is not a dir
 static lfs_stag_t lfs_dir_find(lfs_t *lfs, lfs_mdir_t *dir,
         const char **path, uint16_t *id) {
     // we reduce path to a single name if we can find it
     const char *name = *path;
-    if (id) {
-        *id = 0x3ff;
-    }
 
     // default to root dir
     lfs_stag_t tag = LFS_MKTAG(LFS_TYPE_DIR, 0x3ff, 0);
     dir->tail[0] = lfs->root[0];
     dir->tail[1] = lfs->root[1];
 
+    // empty paths are not allowed
+    if (*name == '\0') {
+        return LFS_ERR_INVAL;
+    }
+
     while (true) {
 nextname:
-        // skip slashes
-        name += strspn(name, "/");
+        // skip slashes if we're a directory
+        if (lfs_tag_type3(tag) == LFS_TYPE_DIR) {
+            name += strspn(name, "/");
+        }
         lfs_size_t namelen = strcspn(name, "/");
 
-        // skip '.' and root '..'
-        if ((namelen == 1 && memcmp(name, ".", 1) == 0) ||
-            (namelen == 2 && memcmp(name, "..", 2) == 0)) {
+        // skip '.'
+        if (namelen == 1 && memcmp(name, ".", 1) == 0) {
             name += namelen;
             goto nextname;
         }
 
+        // error on unmatched '..', trying to go above root?
+        if (namelen == 2 && memcmp(name, "..", 2) == 0) {
+            return LFS_ERR_INVAL;
+        }
+
         // skip if matched by '..' in name
         const char *suffix = name + namelen;
         lfs_size_t sufflen;
@@ -1498,7 +1527,9 @@ nextname:
                 break;
             }
 
-            if (sufflen == 2 && memcmp(suffix, "..", 2) == 0) {
+            if (sufflen == 1 && memcmp(suffix, ".", 1) == 0) {
+                // noop
+            } else if (sufflen == 2 && memcmp(suffix, "..", 2) == 0) {
                 depth -= 1;
                 if (depth == 0) {
                     name = suffix + sufflen;
@@ -1512,14 +1543,14 @@ nextname:
         }
 
         // found path
-        if (name[0] == '\0') {
+        if (*name == '\0') {
             return tag;
         }
 
         // update what we've found so far
         *path = name;
 
-        // only continue if we hit a directory
+        // only continue if we're a directory
         if (lfs_tag_type3(tag) != LFS_TYPE_DIR) {
             return LFS_ERR_NOTDIR;
         }
@@ -1539,8 +1570,7 @@ nextname:
             tag = lfs_dir_fetchmatch(lfs, dir, dir->tail,
                     LFS_MKTAG(0x780, 0, 0),
                     LFS_MKTAG(LFS_TYPE_NAME, 0, namelen),
-                     // are we last name?
-                    (strchr(name, '/') == NULL) ? id : NULL,
+                    id,
                     lfs_dir_find_match, &(struct lfs_dir_find_match){
                         lfs, name, namelen});
             if (tag < 0) {
@@ -2191,7 +2221,8 @@ static int lfs_dir_splittingcompact(lfs_t *lfs, lfs_mdir_t *dir,
                 // we can do, we'll error later if we've become frozen
                 LFS_WARN("Unable to expand superblock");
             } else {
-                end = begin;
+                // duplicate the superblock entry into the new superblock
+                end = 1;
             }
         }
     }
@@ -2358,7 +2389,9 @@ fixmlist:;
 
             while (d->id >= d->m.count && d->m.split) {
                 // we split and id is on tail now
-                d->id -= d->m.count;
+                if (lfs_pair_cmp(d->m.tail, lfs->root) != 0) {
+                    d->id -= d->m.count;
+                }
                 int err = lfs_dir_fetch(lfs, &d->m, d->m.tail);
                 if (err) {
                     return err;
@@ -2600,12 +2633,12 @@ static int lfs_mkdir_(lfs_t *lfs, const char *path) {
     cwd.next = lfs->mlist;
     uint16_t id;
     err = lfs_dir_find(lfs, &cwd.m, &path, &id);
-    if (!(err == LFS_ERR_NOENT && id != 0x3ff)) {
+    if (!(err == LFS_ERR_NOENT && lfs_path_islast(path))) {
         return (err < 0) ? err : LFS_ERR_EXIST;
     }
 
     // check that name fits
-    lfs_size_t nlen = strlen(path);
+    lfs_size_t nlen = lfs_path_namelen(path);
     if (nlen > lfs->name_max) {
         return LFS_ERR_NAMETOOLONG;
     }
@@ -3054,7 +3087,7 @@ static int lfs_file_opencfg_(lfs_t *lfs, lfs_file_t *file,
 
     // allocate entry for file if it doesn't exist
     lfs_stag_t tag = lfs_dir_find(lfs, &file->m, &path, &file->id);
-    if (tag < 0 && !(tag == LFS_ERR_NOENT && file->id != 0x3ff)) {
+    if (tag < 0 && !(tag == LFS_ERR_NOENT && lfs_path_islast(path))) {
         err = tag;
         goto cleanup;
     }
@@ -3074,8 +3107,14 @@ static int lfs_file_opencfg_(lfs_t *lfs, lfs_file_t *file,
             goto cleanup;
         }
 
+        // don't allow trailing slashes
+        if (lfs_path_isdir(path)) {
+            err = LFS_ERR_NOTDIR;
+            goto cleanup;
+        }
+
         // check that name fits
-        lfs_size_t nlen = strlen(path);
+        lfs_size_t nlen = lfs_path_namelen(path);
         if (nlen > lfs->name_max) {
             err = LFS_ERR_NAMETOOLONG;
             goto cleanup;
@@ -3839,6 +3878,12 @@ static int lfs_stat_(lfs_t *lfs, const char *path, struct lfs_info *info) {
         return (int)tag;
     }
 
+    // only allow trailing slashes on dirs
+    if (strchr(path, '/') != NULL
+            && lfs_tag_type3(tag) != LFS_TYPE_DIR) {
+        return LFS_ERR_NOTDIR;
+    }
+
     return lfs_dir_getinfo(lfs, &cwd, lfs_tag_id(tag), info);
 }
 
@@ -3941,7 +3986,7 @@ static int lfs_rename_(lfs_t *lfs, const char *oldpath, const char *newpath) {
     uint16_t newid;
     lfs_stag_t prevtag = lfs_dir_find(lfs, &newcwd, &newpath, &newid);
     if ((prevtag < 0 || lfs_tag_id(prevtag) == 0x3ff) &&
-            !(prevtag == LFS_ERR_NOENT && newid != 0x3ff)) {
+            !(prevtag == LFS_ERR_NOENT && lfs_path_islast(newpath))) {
         return (prevtag < 0) ? (int)prevtag : LFS_ERR_INVAL;
     }
 
@@ -3952,8 +3997,14 @@ static int lfs_rename_(lfs_t *lfs, const char *oldpath, const char *newpath) {
     struct lfs_mlist prevdir;
     prevdir.next = lfs->mlist;
     if (prevtag == LFS_ERR_NOENT) {
+        // if we're a file, don't allow trailing slashes
+        if (lfs_path_isdir(newpath)
+                && lfs_tag_type3(oldtag) != LFS_TYPE_DIR) {
+            return LFS_ERR_NOTDIR;
+        }
+
         // check that name fits
-        lfs_size_t nlen = strlen(newpath);
+        lfs_size_t nlen = lfs_path_namelen(newpath);
         if (nlen > lfs->name_max) {
             return LFS_ERR_NAMETOOLONG;
         }
@@ -4013,7 +4064,8 @@ static int lfs_rename_(lfs_t *lfs, const char *oldpath, const char *newpath) {
             {LFS_MKTAG_IF(prevtag != LFS_ERR_NOENT,
                 LFS_TYPE_DELETE, newid, 0), NULL},
             {LFS_MKTAG(LFS_TYPE_CREATE, newid, 0), NULL},
-            {LFS_MKTAG(lfs_tag_type3(oldtag), newid, strlen(newpath)), newpath},
+            {LFS_MKTAG(lfs_tag_type3(oldtag),
+                newid, lfs_path_namelen(newpath)), newpath},
             {LFS_MKTAG(LFS_FROM_MOVE, newid, lfs_tag_id(oldtag)), &oldcwd},
             {LFS_MKTAG_IF(samepair,
                 LFS_TYPE_DELETE, newoldid, 0), NULL}));
@@ -4466,6 +4518,7 @@ static int lfs_mount_(lfs_t *lfs, const struct lfs_config *cfg) {
             // found older minor version? set an in-device only bit in the
             // gstate so we know we need to rewrite the superblock before
             // the first write
+            bool needssuperblock = false;
             if (minor_version < lfs_fs_disk_version_minor(lfs)) {
                 LFS_DEBUG("Found older minor version "
                         "v%"PRIu16".%"PRIu16" < v%"PRIu16".%"PRIu16,
@@ -4473,10 +4526,11 @@ static int lfs_mount_(lfs_t *lfs, const struct lfs_config *cfg) {
                         minor_version,
                         lfs_fs_disk_version_major(lfs),
                         lfs_fs_disk_version_minor(lfs));
-                // note this bit is reserved on disk, so fetching more gstate
-                // will not interfere here
-                lfs_fs_prepsuperblock(lfs, true);
+                needssuperblock = true;
             }
+            // note this bit is reserved on disk, so fetching more gstate
+            // will not interfere here
+            lfs_fs_prepsuperblock(lfs, needssuperblock);
 
             // check superblock configuration
             if (superblock.name_max) {

tests/test_superblocks.toml

@@ -14,6 +14,24 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
+# make sure the magic string "littlefs" is always at offset=8
+[cases.test_superblocks_magic]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+
+    // check our magic string
+    //
+    // note if we lose power we may not have the magic string in both blocks!
+    // but we don't lose power in this test so we can assert the magic string
+    // is present in both
+    uint8_t magic[lfs_max(16, READ_SIZE)];
+    cfg->read(cfg, 0, 0, magic, lfs_max(16, READ_SIZE)) => 0;
+    assert(memcmp(&magic[8], "littlefs", 8) == 0);
+    cfg->read(cfg, 1, 0, magic, lfs_max(16, READ_SIZE)) => 0;
+    assert(memcmp(&magic[8], "littlefs", 8) == 0);
+'''
+
 # mount/unmount from interpretting a previous superblock block_count
 [cases.test_superblocks_mount_unknown_block_count]
 code = '''
@@ -28,7 +46,6 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
-
 # reentrant format
 [cases.test_superblocks_reentrant_format]
 reentrant = true
@@ -135,6 +152,39 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
+# make sure the magic string "littlefs" is always at offset=8
+[cases.test_superblocks_magic_expand]
+defines.BLOCK_CYCLES = [32, 33, 1]
+defines.N = [10, 100, 1000]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+    lfs_mount(&lfs, cfg) => 0;
+    for (int i = 0; i < N; i++) {
+        lfs_file_t file;
+        lfs_file_open(&lfs, &file, "dummy",
+                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
+        lfs_file_close(&lfs, &file) => 0;
+        struct lfs_info info;
+        lfs_stat(&lfs, "dummy", &info) => 0;
+        assert(strcmp(info.name, "dummy") == 0);
+        assert(info.type == LFS_TYPE_REG);
+        lfs_remove(&lfs, "dummy") => 0;
+    }
+    lfs_unmount(&lfs) => 0;
+
+    // check our magic string
+    //
+    // note if we lose power we may not have the magic string in both blocks!
+    // but we don't lose power in this test so we can assert the magic string
+    // is present in both
+    uint8_t magic[lfs_max(16, READ_SIZE)];
+    cfg->read(cfg, 0, 0, magic, lfs_max(16, READ_SIZE)) => 0;
+    assert(memcmp(&magic[8], "littlefs", 8) == 0);
+    cfg->read(cfg, 1, 0, magic, lfs_max(16, READ_SIZE)) => 0;
+    assert(memcmp(&magic[8], "littlefs", 8) == 0);
+'''
+
 # expanding superblock with power cycle
 [cases.test_superblocks_expand_power_cycle]
 defines.BLOCK_CYCLES = [32, 33, 1]
@@ -221,6 +271,7 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
+
 # mount with unknown block_count
 [cases.test_superblocks_unknown_blocks]
 code = '''