Merge pull request #1058 from littlefs-project/fix-seek-eob-cache

Fixed incorrect cache reuse when seeking from end-of-block

.github/workflows/test.yml

@@ -273,7 +273,6 @@ jobs:
             }' | tee status/$(basename $f .csv).json
           done
       - name: upload-status-sizes
-        if: ${{matrix.arch == 'x86_64'}}
         uses: actions/upload-artifact@v4
         with:
           name: status-sizes-${{matrix.arch}}

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) {
@@ -2128,13 +2158,14 @@ static int lfs_dir_splittingcompact(lfs_t *lfs, lfs_mdir_t *dir,
             // And we cap at half a block to avoid degenerate cases with
             // nearly-full metadata blocks.
             //
+            lfs_size_t metadata_max = (lfs->cfg->metadata_max)
+                    ? lfs->cfg->metadata_max
+                    : lfs->cfg->block_size;
             if (end - split < 0xff
                     && size <= lfs_min(
-                        lfs->cfg->block_size - 40,
+                        metadata_max - 40,
                         lfs_alignup(
-                            (lfs->cfg->metadata_max
-                                ? lfs->cfg->metadata_max
-                                : lfs->cfg->block_size)/2,
+                            metadata_max/2,
                             lfs->cfg->prog_size))) {
                 break;
             }
@@ -2603,12 +2634,12 @@ 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;
     }
@@ -3057,7 +3088,7 @@ 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;
     }
@@ -3077,8 +3108,14 @@ 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;
@@ -3664,22 +3701,16 @@ static lfs_ssize_t lfs_file_write_(lfs_t *lfs, lfs_file_t *file,
 static lfs_soff_t lfs_file_seek_(lfs_t *lfs, lfs_file_t *file,
         lfs_soff_t off, int whence) {
     // find new pos
+    //
+    // fortunately for us, littlefs is limited to 31-bit file sizes, so we
+    // don't have to worry too much about integer overflow
     lfs_off_t npos = file->pos;
     if (whence == LFS_SEEK_SET) {
         npos = off;
     } else if (whence == LFS_SEEK_CUR) {
-        if ((lfs_soff_t)file->pos + off < 0) {
-            return LFS_ERR_INVAL;
-        } else {
-            npos = file->pos + off;
-        }
+        npos = file->pos + (lfs_off_t)off;
     } else if (whence == LFS_SEEK_END) {
-        lfs_soff_t res = lfs_file_size_(lfs, file) + off;
-        if (res < 0) {
-            return LFS_ERR_INVAL;
-        } else {
-            npos = res;
-        }
+        npos = (lfs_off_t)lfs_file_size_(lfs, file) + (lfs_off_t)off;
     }
 
     if (npos > lfs->file_max) {
@@ -3694,13 +3725,8 @@ static lfs_soff_t lfs_file_seek_(lfs_t *lfs, lfs_file_t *file,
 
     // if we're only reading and our new offset is still in the file's cache
     // we can avoid flushing and needing to reread the data
-    if (
-#ifndef LFS_READONLY
-        !(file->flags & LFS_F_WRITING)
-#else
-        true
-#endif
-            ) {
+    if ((file->flags & LFS_F_READING)
+            && file->off != lfs->cfg->block_size) {
         int oindex = lfs_ctz_index(lfs, &(lfs_off_t){file->pos});
         lfs_off_t noff = npos;
         int nindex = lfs_ctz_index(lfs, &noff);
@@ -3842,6 +3868,12 @@ 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);
 }
 
@@ -3944,7 +3976,7 @@ 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;
     }
 
@@ -3955,8 +3987,14 @@ 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;
         }
@@ -4016,7 +4054,8 @@ 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}));
@@ -4173,6 +4212,14 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     // which littlefs currently does not support
     LFS_ASSERT((bool)0x80000000);
 
+    // check that the required io functions are provided
+    LFS_ASSERT(lfs->cfg->read != NULL);
+#ifndef LFS_READONLY
+    LFS_ASSERT(lfs->cfg->prog != NULL);
+    LFS_ASSERT(lfs->cfg->erase != NULL);
+    LFS_ASSERT(lfs->cfg->sync != NULL);
+#endif
+
     // validate that the lfs-cfg sizes were initiated properly before
     // performing any arithmetic logics with them
     LFS_ASSERT(lfs->cfg->read_size != 0);
@@ -4209,6 +4256,15 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
     LFS_ASSERT(lfs->cfg->compact_thresh == (lfs_size_t)-1
             || lfs->cfg->compact_thresh <= lfs->cfg->block_size);
 
+    // check that metadata_max is a multiple of read_size and prog_size,
+    // and a factor of the block_size
+    LFS_ASSERT(!lfs->cfg->metadata_max
+            || lfs->cfg->metadata_max % lfs->cfg->read_size == 0);
+    LFS_ASSERT(!lfs->cfg->metadata_max
+            || lfs->cfg->metadata_max % lfs->cfg->prog_size == 0);
+    LFS_ASSERT(!lfs->cfg->metadata_max
+            || lfs->cfg->block_size % lfs->cfg->metadata_max == 0);
+
     // setup read cache
     if (lfs->cfg->read_buffer) {
         lfs->rcache.buffer = lfs->cfg->read_buffer;
@@ -4396,6 +4452,30 @@ cleanup:
 }
 #endif
 
+struct lfs_tortoise_t {
+    lfs_block_t pair[2];
+    lfs_size_t i;
+    lfs_size_t period;
+};
+
+static int lfs_tortoise_detectcycles(
+    const lfs_mdir_t *dir, struct lfs_tortoise_t *tortoise) {
+    // detect cycles with Brent's algorithm
+    if (lfs_pair_issync(dir->tail, tortoise->pair)) {
+        LFS_WARN("Cycle detected in tail list");
+        return LFS_ERR_CORRUPT;
+    }
+    if (tortoise->i == tortoise->period) {
+        tortoise->pair[0] = dir->tail[0];
+        tortoise->pair[1] = dir->tail[1];
+        tortoise->i = 0;
+        tortoise->period *= 2;
+    }
+    tortoise->i += 1;
+
+    return LFS_ERR_OK;
+}
+
 static int lfs_mount_(lfs_t *lfs, const struct lfs_config *cfg) {
     int err = lfs_init(lfs, cfg);
     if (err) {
@@ -4404,23 +4484,16 @@ static int lfs_mount_(lfs_t *lfs, const struct lfs_config *cfg) {
 
     // scan directory blocks for superblock and any global updates
     lfs_mdir_t dir = {.tail = {0, 1}};
-    lfs_block_t tortoise[2] = {LFS_BLOCK_NULL, LFS_BLOCK_NULL};
-    lfs_size_t tortoise_i = 1;
-    lfs_size_t tortoise_period = 1;
+    struct lfs_tortoise_t tortoise = {
+        .pair = {LFS_BLOCK_NULL, LFS_BLOCK_NULL},
+        .i = 1,
+        .period = 1,
+    };
     while (!lfs_pair_isnull(dir.tail)) {
-        // detect cycles with Brent's algorithm
-        if (lfs_pair_issync(dir.tail, tortoise)) {
-            LFS_WARN("Cycle detected in tail list");
-            err = LFS_ERR_CORRUPT;
+        err = lfs_tortoise_detectcycles(&dir, &tortoise);
+        if (err < 0) {
             goto cleanup;
         }
-        if (tortoise_i == tortoise_period) {
-            tortoise[0] = dir.tail[0];
-            tortoise[1] = dir.tail[1];
-            tortoise_i = 0;
-            tortoise_period *= 2;
-        }
-        tortoise_i += 1;
 
         // fetch next block in tail list
         lfs_stag_t tag = lfs_dir_fetchmatch(lfs, &dir, dir.tail,
@@ -4633,22 +4706,17 @@ int lfs_fs_traverse_(lfs_t *lfs,
     }
 #endif
 
-    lfs_block_t tortoise[2] = {LFS_BLOCK_NULL, LFS_BLOCK_NULL};
-    lfs_size_t tortoise_i = 1;
-    lfs_size_t tortoise_period = 1;
+    struct lfs_tortoise_t tortoise = {
+        .pair = {LFS_BLOCK_NULL, LFS_BLOCK_NULL},
+        .i = 1,
+        .period = 1,
+    };
+    int err = LFS_ERR_OK;
     while (!lfs_pair_isnull(dir.tail)) {
-        // detect cycles with Brent's algorithm
-        if (lfs_pair_issync(dir.tail, tortoise)) {
-            LFS_WARN("Cycle detected in tail list");
+        err = lfs_tortoise_detectcycles(&dir, &tortoise);
+        if (err < 0) {
             return LFS_ERR_CORRUPT;
         }
-        if (tortoise_i == tortoise_period) {
-            tortoise[0] = dir.tail[0];
-            tortoise[1] = dir.tail[1];
-            tortoise_i = 0;
-            tortoise_period *= 2;
-        }
-        tortoise_i += 1;
 
         for (int i = 0; i < 2; i++) {
             int err = cb(data, dir.tail[i]);
@@ -4727,22 +4795,17 @@ static int lfs_fs_pred(lfs_t *lfs,
     // iterate over all directory directory entries
     pdir->tail[0] = 0;
     pdir->tail[1] = 1;
-    lfs_block_t tortoise[2] = {LFS_BLOCK_NULL, LFS_BLOCK_NULL};
-    lfs_size_t tortoise_i = 1;
-    lfs_size_t tortoise_period = 1;
+    struct lfs_tortoise_t tortoise = {
+        .pair = {LFS_BLOCK_NULL, LFS_BLOCK_NULL},
+        .i = 1,
+        .period = 1,
+    };
+    int err = LFS_ERR_OK;
     while (!lfs_pair_isnull(pdir->tail)) {
-        // detect cycles with Brent's algorithm
-        if (lfs_pair_issync(pdir->tail, tortoise)) {
-            LFS_WARN("Cycle detected in tail list");
+        err = lfs_tortoise_detectcycles(pdir, &tortoise);
+        if (err < 0) {
             return LFS_ERR_CORRUPT;
         }
-        if (tortoise_i == tortoise_period) {
-            tortoise[0] = pdir->tail[0];
-            tortoise[1] = pdir->tail[1];
-            tortoise_i = 0;
-            tortoise_period *= 2;
-        }
-        tortoise_i += 1;
 
         if (lfs_pair_cmp(pdir->tail, pair) == 0) {
             return 0;
@@ -4792,22 +4855,17 @@ static lfs_stag_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t pair[2],
     // use fetchmatch with callback to find pairs
     parent->tail[0] = 0;
     parent->tail[1] = 1;
-    lfs_block_t tortoise[2] = {LFS_BLOCK_NULL, LFS_BLOCK_NULL};
-    lfs_size_t tortoise_i = 1;
-    lfs_size_t tortoise_period = 1;
+    struct lfs_tortoise_t tortoise = {
+        .pair = {LFS_BLOCK_NULL, LFS_BLOCK_NULL},
+        .i = 1,
+        .period = 1,
+    };
+    int err = LFS_ERR_OK;
     while (!lfs_pair_isnull(parent->tail)) {
-        // detect cycles with Brent's algorithm
-        if (lfs_pair_issync(parent->tail, tortoise)) {
-            LFS_WARN("Cycle detected in tail list");
-            return LFS_ERR_CORRUPT;
+        err = lfs_tortoise_detectcycles(parent, &tortoise);
+        if (err < 0) {
+            return err;
         }
-        if (tortoise_i == tortoise_period) {
-            tortoise[0] = parent->tail[0];
-            tortoise[1] = parent->tail[1];
-            tortoise_i = 0;
-            tortoise_period *= 2;
-        }
-        tortoise_i += 1;
 
         lfs_stag_t tag = lfs_dir_fetchmatch(lfs, parent, parent->tail,
                 LFS_MKTAG(0x7ff, 0, 0x3ff),
@@ -5890,7 +5948,7 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
                 ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
                 ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
                 ".block_size=%"PRIu32", .block_count=%"PRIu32", "
-                ".block_cycles=%"PRIu32", .cache_size=%"PRIu32", "
+                ".block_cycles=%"PRId32", .cache_size=%"PRIu32", "
                 ".lookahead_size=%"PRIu32", .read_buffer=%p, "
                 ".prog_buffer=%p, .lookahead_buffer=%p, "
                 ".name_max=%"PRIu32", .file_max=%"PRIu32", "
@@ -5920,7 +5978,7 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
                 ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
                 ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
                 ".block_size=%"PRIu32", .block_count=%"PRIu32", "
-                ".block_cycles=%"PRIu32", .cache_size=%"PRIu32", "
+                ".block_cycles=%"PRId32", .cache_size=%"PRIu32", "
                 ".lookahead_size=%"PRIu32", .read_buffer=%p, "
                 ".prog_buffer=%p, .lookahead_buffer=%p, "
                 ".name_max=%"PRIu32", .file_max=%"PRIu32", "
@@ -6057,7 +6115,7 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file, const char *path, int flags) {
         return err;
     }
     LFS_TRACE("lfs_file_open(%p, %p, \"%s\", %x)",
-            (void*)lfs, (void*)file, path, flags);
+            (void*)lfs, (void*)file, path, (unsigned)flags);
     LFS_ASSERT(!lfs_mlist_isopen(lfs->mlist, (struct lfs_mlist*)file));
 
     err = lfs_file_open_(lfs, file, path, flags);
@@ -6077,7 +6135,7 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
     }
     LFS_TRACE("lfs_file_opencfg(%p, %p, \"%s\", %x, %p {"
                  ".buffer=%p, .attrs=%p, .attr_count=%"PRIu32"})",
-            (void*)lfs, (void*)file, path, flags,
+            (void*)lfs, (void*)file, path, (unsigned)flags,
             (void*)cfg, cfg->buffer, (void*)cfg->attrs, cfg->attr_count);
     LFS_ASSERT(!lfs_mlist_isopen(lfs->mlist, (struct lfs_mlist*)file));
 
@@ -6439,7 +6497,7 @@ int lfs_migrate(lfs_t *lfs, const struct lfs_config *cfg) {
                 ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
                 ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
                 ".block_size=%"PRIu32", .block_count=%"PRIu32", "
-                ".block_cycles=%"PRIu32", .cache_size=%"PRIu32", "
+                ".block_cycles=%"PRId32", .cache_size=%"PRIu32", "
                 ".lookahead_size=%"PRIu32", .read_buffer=%p, "
                 ".prog_buffer=%p, .lookahead_buffer=%p, "
                 ".name_max=%"PRIu32", .file_max=%"PRIu32", "

lfs.h

@@ -21,7 +21,7 @@ extern "C"
 // Software library version
 // Major (top-nibble), incremented on backwards incompatible changes
 // Minor (bottom-nibble), incremented on feature additions
-#define LFS_VERSION 0x00020009
+#define LFS_VERSION 0x0002000a
 #define LFS_VERSION_MAJOR (0xffff & (LFS_VERSION >> 16))
 #define LFS_VERSION_MINOR (0xffff & (LFS_VERSION >>  0))
 

lfs_util.h

@@ -8,6 +8,9 @@
 #ifndef LFS_UTIL_H
 #define LFS_UTIL_H
 
+#define LFS_STRINGIZE(x) LFS_STRINGIZE2(x)
+#define LFS_STRINGIZE2(x) #x
+
 // Users can override lfs_util.h with their own configuration by defining
 // LFS_CONFIG as a header file to include (-DLFS_CONFIG=lfs_config.h).
 //
@@ -15,11 +18,26 @@
 // provided by the config file. To start, I would suggest copying lfs_util.h
 // and modifying as needed.
 #ifdef LFS_CONFIG
-#define LFS_STRINGIZE(x) LFS_STRINGIZE2(x)
-#define LFS_STRINGIZE2(x) #x
 #include LFS_STRINGIZE(LFS_CONFIG)
 #else
 
+// Alternatively, users can provide a header file which defines
+// macros and other things consumed by littlefs.
+//
+// For example, provide my_defines.h, which contains
+// something like:
+//
+// #include <stddef.h>
+// extern void *my_malloc(size_t sz);
+// #define LFS_MALLOC(sz) my_malloc(sz)
+//
+// And build littlefs with the header by defining LFS_DEFINES.
+// (-DLFS_DEFINES=my_defines.h)
+
+#ifdef LFS_DEFINES
+#include LFS_STRINGIZE(LFS_DEFINES)
+#endif
+
 // System includes
 #include <stdint.h>
 #include <stdbool.h>

runners/bench_runner.c

@@ -1322,6 +1322,7 @@ void perm_run(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     };
 

runners/bench_runner.h

@@ -96,12 +96,13 @@ intmax_t bench_define(size_t define);
 #define CACHE_SIZE_i         6
 #define LOOKAHEAD_SIZE_i     7
 #define COMPACT_THRESH_i     8
-#define INLINE_MAX_i         9
-#define BLOCK_CYCLES_i       10
-#define ERASE_VALUE_i        11
-#define ERASE_CYCLES_i       12
-#define BADBLOCK_BEHAVIOR_i  13
-#define POWERLOSS_BEHAVIOR_i 14
+#define METADATA_MAX_i       9
+#define INLINE_MAX_i         10
+#define BLOCK_CYCLES_i       11
+#define ERASE_VALUE_i        12
+#define ERASE_CYCLES_i       13
+#define BADBLOCK_BEHAVIOR_i  14
+#define POWERLOSS_BEHAVIOR_i 15
 
 #define READ_SIZE           bench_define(READ_SIZE_i)
 #define PROG_SIZE           bench_define(PROG_SIZE_i)
@@ -112,6 +113,7 @@ intmax_t bench_define(size_t define);
 #define CACHE_SIZE          bench_define(CACHE_SIZE_i)
 #define LOOKAHEAD_SIZE      bench_define(LOOKAHEAD_SIZE_i)
 #define COMPACT_THRESH      bench_define(COMPACT_THRESH_i)
+#define METADATA_MAX        bench_define(METADATA_MAX_i)
 #define INLINE_MAX          bench_define(INLINE_MAX_i)
 #define BLOCK_CYCLES        bench_define(BLOCK_CYCLES_i)
 #define ERASE_VALUE         bench_define(ERASE_VALUE_i)
@@ -129,6 +131,7 @@ intmax_t bench_define(size_t define);
     BENCH_DEF(CACHE_SIZE,         lfs_max(64,lfs_max(READ_SIZE,PROG_SIZE))) \
     BENCH_DEF(LOOKAHEAD_SIZE,     16) \
     BENCH_DEF(COMPACT_THRESH,     0) \
+    BENCH_DEF(METADATA_MAX,       0) \
     BENCH_DEF(INLINE_MAX,         0) \
     BENCH_DEF(BLOCK_CYCLES,       -1) \
     BENCH_DEF(ERASE_VALUE,        0xff) \
@@ -137,7 +140,7 @@ intmax_t bench_define(size_t define);
     BENCH_DEF(POWERLOSS_BEHAVIOR, LFS_EMUBD_POWERLOSS_NOOP)
 
 #define BENCH_GEOMETRY_DEFINE_COUNT 4
-#define BENCH_IMPLICIT_DEFINE_COUNT 15
+#define BENCH_IMPLICIT_DEFINE_COUNT 16
 
 
 #endif

runners/test_runner.c

@@ -1347,6 +1347,7 @@ static void run_powerloss_none(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     #ifdef LFS_MULTIVERSION
         .disk_version       = DISK_VERSION,
@@ -1425,6 +1426,7 @@ static void run_powerloss_linear(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     #ifdef LFS_MULTIVERSION
         .disk_version       = DISK_VERSION,
@@ -1520,6 +1522,7 @@ static void run_powerloss_log(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     #ifdef LFS_MULTIVERSION
         .disk_version       = DISK_VERSION,
@@ -1613,6 +1616,7 @@ static void run_powerloss_cycles(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     #ifdef LFS_MULTIVERSION
         .disk_version       = DISK_VERSION,
@@ -1804,6 +1808,7 @@ static void run_powerloss_exhaustive(
         .cache_size         = CACHE_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
         .compact_thresh     = COMPACT_THRESH,
+        .metadata_max       = METADATA_MAX,
         .inline_max         = INLINE_MAX,
     #ifdef LFS_MULTIVERSION
         .disk_version       = DISK_VERSION,

runners/test_runner.h

@@ -89,13 +89,14 @@ intmax_t test_define(size_t define);
 #define CACHE_SIZE_i         6
 #define LOOKAHEAD_SIZE_i     7
 #define COMPACT_THRESH_i     8
-#define INLINE_MAX_i         9
-#define BLOCK_CYCLES_i       10
-#define ERASE_VALUE_i        11
-#define ERASE_CYCLES_i       12
-#define BADBLOCK_BEHAVIOR_i  13
-#define POWERLOSS_BEHAVIOR_i 14
-#define DISK_VERSION_i       15
+#define METADATA_MAX_i       9
+#define INLINE_MAX_i         10
+#define BLOCK_CYCLES_i       11
+#define ERASE_VALUE_i        12
+#define ERASE_CYCLES_i       13
+#define BADBLOCK_BEHAVIOR_i  14
+#define POWERLOSS_BEHAVIOR_i 15
+#define DISK_VERSION_i       16
 
 #define READ_SIZE           TEST_DEFINE(READ_SIZE_i)
 #define PROG_SIZE           TEST_DEFINE(PROG_SIZE_i)
@@ -106,6 +107,7 @@ intmax_t test_define(size_t define);
 #define CACHE_SIZE          TEST_DEFINE(CACHE_SIZE_i)
 #define LOOKAHEAD_SIZE      TEST_DEFINE(LOOKAHEAD_SIZE_i)
 #define COMPACT_THRESH      TEST_DEFINE(COMPACT_THRESH_i)
+#define METADATA_MAX        TEST_DEFINE(METADATA_MAX_i)
 #define INLINE_MAX          TEST_DEFINE(INLINE_MAX_i)
 #define BLOCK_CYCLES        TEST_DEFINE(BLOCK_CYCLES_i)
 #define ERASE_VALUE         TEST_DEFINE(ERASE_VALUE_i)
@@ -124,6 +126,7 @@ intmax_t test_define(size_t define);
     TEST_DEF(CACHE_SIZE,         lfs_max(64,lfs_max(READ_SIZE,PROG_SIZE))) \
     TEST_DEF(LOOKAHEAD_SIZE,     16) \
     TEST_DEF(COMPACT_THRESH,     0) \
+    TEST_DEF(METADATA_MAX,       0) \
     TEST_DEF(INLINE_MAX,         0) \
     TEST_DEF(BLOCK_CYCLES,       -1) \
     TEST_DEF(ERASE_VALUE,        0xff) \
@@ -133,7 +136,7 @@ intmax_t test_define(size_t define);
     TEST_DEF(DISK_VERSION,       0)
 
 #define TEST_GEOMETRY_DEFINE_COUNT 4
-#define TEST_IMPLICIT_DEFINE_COUNT 16
+#define TEST_IMPLICIT_DEFINE_COUNT 17
 
 
 #endif

scripts/prettyasserts.py

@@ -86,6 +86,13 @@ def write_header(f, limit=LIMIT):
     f.writeln("}")
     f.writeln()
     f.writeln("__attribute__((unused))")
+    f.writeln("static void __pretty_assert_print_ptr(")
+    f.writeln("        const void *v, size_t size) {")
+    f.writeln("    (void)size;")
+    f.writeln("    printf(\"%p\", v);")
+    f.writeln("}")
+    f.writeln()
+    f.writeln("__attribute__((unused))")
     f.writeln("static void __pretty_assert_print_mem(")
     f.writeln("        const void *v, size_t size) {")
     f.writeln("    const uint8_t *v_ = v;")
@@ -183,6 +190,23 @@ def write_header(f, limit=LIMIT):
         f.writeln("                _rh, strlen(_rh)); \\")
         f.writeln("    } \\")
         f.writeln("} while (0)")
+    for op, cmp in sorted(CMP.items()):
+        # Only EQ and NE are supported when compared to NULL.
+        if cmp not in ['eq', 'ne']:
+            continue
+        f.writeln("#define __PRETTY_ASSERT_PTR_%s(lh, rh) do { \\"
+            % cmp.upper())
+        f.writeln("    const void *_lh = (const void*)(uintptr_t)lh; \\")
+        f.writeln("    const void *_rh = (const void*)(uintptr_t)rh; \\")
+        f.writeln("    if (!(_lh %s _rh)) { \\" % op)
+        f.writeln("        __pretty_assert_fail( \\")
+        f.writeln("                __FILE__, __LINE__, \\")
+        f.writeln("                __pretty_assert_print_ptr, \"%s\", \\"
+            % cmp)
+        f.writeln("                (const void*){_lh}, 0, \\")
+        f.writeln("                (const void*){_rh}, 0); \\")
+        f.writeln("    } \\")
+        f.writeln("} while (0)")
     f.writeln()
     f.writeln()
 
@@ -301,6 +325,8 @@ def p_assert(p):
         cmp = p.expect('cmp') ; p.accept('ws')
         rh = p_expr(p) ; p.accept('ws')
         p.expect(')')
+        if rh == 'NULL' or lh == 'NULL':
+            return mkassert('ptr', CMP[cmp], lh, rh)
         return mkassert('int', CMP[cmp], lh, rh)
     except ParseFailure:
         p.pop(state)

tests/test_seek.toml

@@ -137,6 +137,130 @@ code = '''
     lfs_unmount(&lfs) => 0;
 '''
 
+# boundary seek and reads
+[cases.test_seek_boundary_read]
+defines.COUNT = 132
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "kitty",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    size_t size = strlen("kittycatcat");
+    uint8_t buffer[1024];
+    memcpy(buffer, "kittycatcat", size);
+    for (int j = 0; j < COUNT; j++) {
+        lfs_file_write(&lfs, &file, buffer, size);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_file_open(&lfs, &file, "kitty", LFS_O_RDONLY) => 0;
+
+    size = strlen("kittycatcat");
+    const lfs_soff_t offsets[] = {
+        512,
+        1024-4,
+        512+1,
+        1024-4+1,
+        512-1,
+        1024-4-1,
+
+        512-strlen("kittycatcat"),
+        1024-4-strlen("kittycatcat"),
+        512-strlen("kittycatcat")+1,
+        1024-4-strlen("kittycatcat")+1,
+        512-strlen("kittycatcat")-1,
+        1024-4-strlen("kittycatcat")-1,
+
+        strlen("kittycatcat")*(COUNT-2)-1,
+    };
+
+    for (unsigned i = 0; i < sizeof(offsets) / sizeof(offsets[0]); i++) {
+        lfs_soff_t off = offsets[i];
+        // read @ offset
+        lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[off % strlen("kittycatcat")],
+                size) => 0;
+        // read after
+        lfs_file_seek(&lfs, &file, off+strlen("kittycatcat")+1, LFS_SEEK_SET)
+                => off+strlen("kittycatcat")+1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off+1) % strlen("kittycatcat")],
+                size) => 0;
+        // read before
+        lfs_file_seek(&lfs, &file, off-strlen("kittycatcat")-1, LFS_SEEK_SET)
+                => off-strlen("kittycatcat")-1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off-1) % strlen("kittycatcat")],
+                size) => 0;
+
+        // read @ 0
+        lfs_file_seek(&lfs, &file, 0, LFS_SEEK_SET) => 0;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer, "kittycatcat", size) => 0;
+
+        // read @ offset
+        lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[off % strlen("kittycatcat")],
+                size) => 0;
+        // read after
+        lfs_file_seek(&lfs, &file, off+strlen("kittycatcat")+1, LFS_SEEK_SET)
+                => off+strlen("kittycatcat")+1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off+1) % strlen("kittycatcat")],
+                size) => 0;
+        // read before
+        lfs_file_seek(&lfs, &file, off-strlen("kittycatcat")-1, LFS_SEEK_SET)
+                => off-strlen("kittycatcat")-1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off-1) % strlen("kittycatcat")],
+                size) => 0;
+
+        // sync
+        lfs_file_sync(&lfs, &file) => 0;
+
+        // read @ 0
+        lfs_file_seek(&lfs, &file, 0, LFS_SEEK_SET) => 0;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer, "kittycatcat", size) => 0;
+
+        // read @ offset
+        lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[off % strlen("kittycatcat")],
+                size) => 0;
+        // read after
+        lfs_file_seek(&lfs, &file, off+strlen("kittycatcat")+1, LFS_SEEK_SET)
+                => off+strlen("kittycatcat")+1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off+1) % strlen("kittycatcat")],
+                size) => 0;
+        // read before
+        lfs_file_seek(&lfs, &file, off-strlen("kittycatcat")-1, LFS_SEEK_SET)
+                => off-strlen("kittycatcat")-1;
+        lfs_file_read(&lfs, &file, buffer, size) => size;
+        memcmp(buffer,
+                &"kittycatcatkittycatcat"[(off-1) % strlen("kittycatcat")],
+                size) => 0;
+    }
+
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+'''
+
 # boundary seek and writes
 [cases.test_seek_boundary_write]
 defines.COUNT = 132
@@ -160,31 +284,54 @@ code = '''
     lfs_file_open(&lfs, &file, "kitty", LFS_O_RDWR) => 0;
 
     size = strlen("hedgehoghog");
-    const lfs_soff_t offsets[] = {512, 1020, 513, 1021, 511, 1019, 1441};
+    const lfs_soff_t offsets[] = {
+        512,
+        1024-4,
+        512+1,
+        1024-4+1,
+        512-1,
+        1024-4-1,
+
+        512-strlen("kittycatcat"),
+        1024-4-strlen("kittycatcat"),
+        512-strlen("kittycatcat")+1,
+        1024-4-strlen("kittycatcat")+1,
+        512-strlen("kittycatcat")-1,
+        1024-4-strlen("kittycatcat")-1,
+
+        strlen("kittycatcat")*(COUNT-2)-1,
+    };
 
     for (unsigned i = 0; i < sizeof(offsets) / sizeof(offsets[0]); i++) {
         lfs_soff_t off = offsets[i];
+        // write @ offset
         memcpy(buffer, "hedgehoghog", size);
         lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
         lfs_file_write(&lfs, &file, buffer, size) => size;
+
+        // read @ offset
         lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
         lfs_file_read(&lfs, &file, buffer, size) => size;
         memcmp(buffer, "hedgehoghog", size) => 0;
 
+        // read @ 0
         lfs_file_seek(&lfs, &file, 0, LFS_SEEK_SET) => 0;
         lfs_file_read(&lfs, &file, buffer, size) => size;
         memcmp(buffer, "kittycatcat", size) => 0;
 
+        // read @ offset
         lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
         lfs_file_read(&lfs, &file, buffer, size) => size;
         memcmp(buffer, "hedgehoghog", size) => 0;
 
         lfs_file_sync(&lfs, &file) => 0;
 
+        // read @ 0
         lfs_file_seek(&lfs, &file, 0, LFS_SEEK_SET) => 0;
         lfs_file_read(&lfs, &file, buffer, size) => size;
         memcmp(buffer, "kittycatcat", size) => 0;
 
+        // read @ offset
         lfs_file_seek(&lfs, &file, off, LFS_SEEK_SET) => off;
         lfs_file_read(&lfs, &file, buffer, size) => size;
         memcmp(buffer, "hedgehoghog", size) => 0;
@@ -405,3 +552,111 @@ code = '''
     lfs_file_close(&lfs, &file) => 0;
     lfs_unmount(&lfs) => 0;
 '''
+
+
+# test possible overflow/underflow conditions
+#
+# note these need -fsanitize=undefined to consistently detect
+# overflow/underflow conditions
+
+[cases.test_seek_filemax]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "kitty",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    uint8_t buffer[1024];
+    strcpy((char*)buffer, "kittycatcat");
+    size_t size = strlen((char*)buffer);
+    lfs_file_write(&lfs, &file, buffer, size) => size;
+
+    // seek with LFS_SEEK_SET
+    lfs_file_seek(&lfs, &file, LFS_FILE_MAX, LFS_SEEK_SET) => LFS_FILE_MAX;
+
+    // seek with LFS_SEEK_CUR
+    lfs_file_seek(&lfs, &file, 0, LFS_SEEK_CUR) => LFS_FILE_MAX;
+
+    // the file hasn't changed size, so seek end takes us back to the offset=0
+    lfs_file_seek(&lfs, &file, +10, LFS_SEEK_END) => size+10;
+
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+'''
+
+[cases.test_seek_underflow]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "kitty",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    uint8_t buffer[1024];
+    strcpy((char*)buffer, "kittycatcat");
+    size_t size = strlen((char*)buffer);
+    lfs_file_write(&lfs, &file, buffer, size) => size;
+
+    // underflow with LFS_SEEK_CUR, should error
+    lfs_file_seek(&lfs, &file, -(size+10), LFS_SEEK_CUR) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, -LFS_FILE_MAX, LFS_SEEK_CUR) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, -(size+LFS_FILE_MAX), LFS_SEEK_CUR)
+            => LFS_ERR_INVAL;
+
+    // underflow with LFS_SEEK_END, should error
+    lfs_file_seek(&lfs, &file, -(size+10), LFS_SEEK_END) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, -LFS_FILE_MAX, LFS_SEEK_END) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, -(size+LFS_FILE_MAX), LFS_SEEK_END)
+            => LFS_ERR_INVAL;
+
+    // file pointer should not have changed
+    lfs_file_tell(&lfs, &file) => size;
+
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+'''
+
+[cases.test_seek_overflow]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "kitty",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    uint8_t buffer[1024];
+    strcpy((char*)buffer, "kittycatcat");
+    size_t size = strlen((char*)buffer);
+    lfs_file_write(&lfs, &file, buffer, size) => size;
+
+    // seek to LFS_FILE_MAX
+    lfs_file_seek(&lfs, &file, LFS_FILE_MAX, LFS_SEEK_SET) => LFS_FILE_MAX;
+
+    // overflow with LFS_SEEK_CUR, should error
+    lfs_file_seek(&lfs, &file, +10, LFS_SEEK_CUR) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, +LFS_FILE_MAX, LFS_SEEK_CUR) => LFS_ERR_INVAL;
+
+    // LFS_SEEK_SET/END don't care about the current file position, but we can
+    // still overflow with a large offset
+
+    // overflow with LFS_SEEK_SET, should error
+    lfs_file_seek(&lfs, &file,
+            +((uint32_t)LFS_FILE_MAX+10),
+            LFS_SEEK_SET) => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file,
+            +((uint32_t)LFS_FILE_MAX+(uint32_t)LFS_FILE_MAX),
+            LFS_SEEK_SET) => LFS_ERR_INVAL;
+
+    // overflow with LFS_SEEK_END, should error
+    lfs_file_seek(&lfs, &file, +(LFS_FILE_MAX-size+10), LFS_SEEK_END)
+            => LFS_ERR_INVAL;
+    lfs_file_seek(&lfs, &file, +(LFS_FILE_MAX-size+LFS_FILE_MAX), LFS_SEEK_END)
+            => LFS_ERR_INVAL;
+
+    // file pointer should not have changed
+    lfs_file_tell(&lfs, &file) => LFS_FILE_MAX;
+
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+'''

tests/test_superblocks.toml

@@ -523,3 +523,30 @@ code = '''
     assert(memcmp(buffer, "hello!", 6) == 0);
     lfs_unmount(&lfs) => 0;
 '''
+
+# test that metadata_max does not cause problems for superblock compaction
+[cases.test_superblocks_metadata_max]
+defines.METADATA_MAX = [
+    'lfs_max(512, PROG_SIZE)',
+    'lfs_max(BLOCK_SIZE/2, PROG_SIZE)',
+    'BLOCK_SIZE'
+]
+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;
+        char name[256];
+        sprintf(name, "hello%03x", i);
+        lfs_file_open(&lfs, &file, name,
+                LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
+        lfs_file_close(&lfs, &file) => 0;
+        struct lfs_info info;
+        lfs_stat(&lfs, name, &info) => 0;
+        assert(strcmp(info.name, name) == 0);
+        assert(info.type == LFS_TYPE_REG);
+    }
+    lfs_unmount(&lfs) => 0;
+'''