Stop wear-leveling during migration

Stop proactively relocate blocks during migrations, this can cause a number of
failure states such: clobbering the v1 superblock if we relocate root, and
invalidating directory pointers if we relocate the head of a directory. On top
of this, relocations increase the overall complexity of lfs_migration, which is
already a delicate operation.

README.md

@@ -53,6 +53,7 @@ const struct lfs_config cfg = {
     .block_count = 128,
     .cache_size = 16,
     .lookahead_size = 16,
+    .block_cycles = 500,
 };
 
 // entry point

lfs.c

@@ -977,7 +977,7 @@ static int lfs_dir_fetch(lfs_t *lfs,
         lfs_mdir_t *dir, const lfs_block_t pair[2]) {
     // note, mask=-1, tag=0 can never match a tag since this
     // pattern has the invalid bit set
-    return lfs_dir_fetchmatch(lfs, dir, pair, -1, 0, NULL, NULL, NULL);
+    return (int)lfs_dir_fetchmatch(lfs, dir, pair, -1, 0, NULL, NULL, NULL);
 }
 
 static int lfs_dir_getgstate(lfs_t *lfs, const lfs_mdir_t *dir,
@@ -1010,7 +1010,7 @@ static int lfs_dir_getinfo(lfs_t *lfs, lfs_mdir_t *dir,
     lfs_stag_t tag = lfs_dir_get(lfs, dir, LFS_MKTAG(0x780, 0x3ff, 0),
             LFS_MKTAG(LFS_TYPE_NAME, id, lfs->name_max+1), info->name);
     if (tag < 0) {
-        return tag;
+        return (int)tag;
     }
 
     info->type = lfs_tag_type3(tag);
@@ -1019,7 +1019,7 @@ static int lfs_dir_getinfo(lfs_t *lfs, lfs_mdir_t *dir,
     tag = lfs_dir_get(lfs, dir, LFS_MKTAG(0x700, 0x3ff, 0),
             LFS_MKTAG(LFS_TYPE_STRUCT, id, sizeof(ctz)), &ctz);
     if (tag < 0) {
-        return tag;
+        return (int)tag;
     }
     lfs_ctz_fromle32(&ctz);
 
@@ -1062,7 +1062,7 @@ static int lfs_dir_find_match(void *data,
     return LFS_CMP_EQ;
 }
 
-static int lfs_dir_find(lfs_t *lfs, lfs_mdir_t *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;
@@ -1503,9 +1503,13 @@ static int lfs_dir_compact(lfs_t *lfs,
                 }
             }
 #ifdef LFS_MIGRATE
-        } else if (lfs_pair_cmp(dir->pair, lfs->root) == 0 && lfs->lfs1) {
+        } else if (lfs->lfs1) {
-            // we can't relocate our root during migrations, as this would
+            // do not proactively relocate blocks during migrations, this
-            // cause the superblock to get updated, which would clobber v1
+            // can cause a number of failure states such: clobbering the
+            // v1 superblock if we relocate root, and invalidating directory
+            // pointers if we relocate the head of a directory. On top of
+            // this, relocations increase the overall complexity of
+            // lfs_migration, which is already a delicate operation.
 #endif
         } else {
             // we're writing too much, time to relocate
@@ -2064,10 +2068,14 @@ int lfs_dir_seek(lfs_t *lfs, lfs_dir_t *dir, lfs_off_t off) {
     dir->pos = lfs_min(2, off);
     off -= dir->pos;
 
-    while (off != 0) {
+    // skip superblock entry
-        dir->id = lfs_min(dir->m.count, off);
+    dir->id = (off > 0 && lfs_pair_cmp(dir->head, lfs->root) == 0);
-        dir->pos += dir->id;
+
-        off -= dir->id;
+    while (off > 0) {
+        int diff = lfs_min(dir->m.count - dir->id, off);
+        dir->id += diff;
+        dir->pos += diff;
+        off -= diff;
 
         if (dir->id == dir->m.count) {
             if (!dir->m.split) {
@@ -2080,6 +2088,8 @@ int lfs_dir_seek(lfs_t *lfs, lfs_dir_t *dir, lfs_off_t off) {
                 LFS_TRACE("lfs_dir_seek -> %d", err);
                 return err;
             }
+
+            dir->id = 0;
         }
     }
 
@@ -3006,10 +3016,10 @@ int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size) {
     } else if (size > oldsize) {
         // flush+seek if not already at end
         if (file->pos != oldsize) {
-            int err = lfs_file_seek(lfs, file, 0, LFS_SEEK_END);
+            lfs_soff_t res = lfs_file_seek(lfs, file, 0, LFS_SEEK_END);
-            if (err < 0) {
+            if (res < 0) {
-                LFS_TRACE("lfs_file_truncate -> %d", err);
+                LFS_TRACE("lfs_file_truncate -> %d", res);
-                return err;
+                return (int)res;
             }
         }
 
@@ -3018,16 +3028,16 @@ int lfs_file_truncate(lfs_t *lfs, lfs_file_t *file, lfs_off_t size) {
             lfs_ssize_t res = lfs_file_write(lfs, file, &(uint8_t){0}, 1);
             if (res < 0) {
                 LFS_TRACE("lfs_file_truncate -> %d", res);
-                return res;
+                return (int)res;
             }
         }
     }
 
     // restore pos
-    int err = lfs_file_seek(lfs, file, pos, LFS_SEEK_SET);
+    lfs_soff_t res = lfs_file_seek(lfs, file, pos, LFS_SEEK_SET);
-    if (err < 0) {
+    if (res < 0) {
-      LFS_TRACE("lfs_file_truncate -> %d", err);
+      LFS_TRACE("lfs_file_truncate -> %d", res);
-      return err;
+      return (int)res;
     }
 
     LFS_TRACE("lfs_file_truncate -> %d", 0);
@@ -3047,7 +3057,7 @@ int lfs_file_rewind(lfs_t *lfs, lfs_file_t *file) {
     lfs_soff_t res = lfs_file_seek(lfs, file, 0, LFS_SEEK_SET);
     if (res < 0) {
         LFS_TRACE("lfs_file_rewind -> %d", res);
-        return res;
+        return (int)res;
     }
 
     LFS_TRACE("lfs_file_rewind -> %d", 0);
@@ -3076,7 +3086,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
     lfs_stag_t tag = lfs_dir_find(lfs, &cwd, &path, NULL);
     if (tag < 0) {
         LFS_TRACE("lfs_stat -> %d", tag);
-        return tag;
+        return (int)tag;
     }
 
     int err = lfs_dir_getinfo(lfs, &cwd, lfs_tag_id(tag), info);
@@ -3097,7 +3107,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
     lfs_stag_t tag = lfs_dir_find(lfs, &cwd, &path, NULL);
     if (tag < 0 || lfs_tag_id(tag) == 0x3ff) {
         LFS_TRACE("lfs_remove -> %d", (tag < 0) ? tag : LFS_ERR_INVAL);
-        return (tag < 0) ? tag : LFS_ERR_INVAL;
+        return (tag < 0) ? (int)tag : LFS_ERR_INVAL;
     }
 
     lfs_mdir_t dir;
@@ -3108,7 +3118,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
                 LFS_MKTAG(LFS_TYPE_STRUCT, lfs_tag_id(tag), 8), pair);
         if (res < 0) {
             LFS_TRACE("lfs_remove -> %d", res);
-            return res;
+            return (int)res;
         }
         lfs_pair_fromle32(pair);
 
@@ -3171,7 +3181,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     lfs_stag_t oldtag = lfs_dir_find(lfs, &oldcwd, &oldpath, NULL);
     if (oldtag < 0 || lfs_tag_id(oldtag) == 0x3ff) {
         LFS_TRACE("lfs_rename -> %d", (oldtag < 0) ? oldtag : LFS_ERR_INVAL);
-        return (oldtag < 0) ? oldtag : LFS_ERR_INVAL;
+        return (oldtag < 0) ? (int)oldtag : LFS_ERR_INVAL;
     }
 
     // find new entry
@@ -3181,7 +3191,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     if ((prevtag < 0 || lfs_tag_id(prevtag) == 0x3ff) &&
             !(prevtag == LFS_ERR_NOENT && newid != 0x3ff)) {
         LFS_TRACE("lfs_rename -> %d", (prevtag < 0) ? prevtag : LFS_ERR_INVAL);
-        return (prevtag < 0) ? prevtag : LFS_ERR_INVAL;
+        return (prevtag < 0) ? (int)prevtag : LFS_ERR_INVAL;
     }
 
     lfs_mdir_t prevdir;
@@ -3202,7 +3212,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
                 LFS_MKTAG(LFS_TYPE_STRUCT, newid, 8), prevpair);
         if (res < 0) {
             LFS_TRACE("lfs_rename -> %d", res);
-            return res;
+            return (int)res;
         }
         lfs_pair_fromle32(prevpair);
 

tests/test_seek.sh

@@ -428,4 +428,78 @@ scripts/test.py << TEST
 TEST
 done
 
+echo "--- Root seek test ---"
+./scripts/test.py << TEST
+    lfs_mount(&lfs, &cfg) => 0;
+    for (int i = 3; i < $MEDIUMSIZE; i++) {
+        sprintf(path, "hi%03d", i);
+        lfs_mkdir(&lfs, path) => 0;
+    }
+
+    lfs_dir_open(&lfs, &dir, "/") => 0;
+    for (int i = 0; i < $MEDIUMSIZE; i++) {
+        if (i == 0) {
+            sprintf(path, ".");
+        } else if (i == 1) {
+            sprintf(path, "..");
+        } else if (i == 2) {
+            sprintf(path, "hello");
+        } else {
+            sprintf(path, "hi%03d", i);
+        }
+        lfs_dir_read(&lfs, &dir, &info) => 1;
+        strcmp(path, info.name) => 0;
+    }
+    lfs_dir_read(&lfs, &dir, &info) => 0;
+    lfs_dir_close(&lfs, &dir) => 0;
+
+    for (int j = 0; j < $MEDIUMSIZE; j++) {
+        lfs_soff_t off = -1;
+
+        lfs_dir_open(&lfs, &dir, "/") => 0;
+        for (int i = 0; i < $MEDIUMSIZE; i++) {
+            if (i == 0) {
+                sprintf(path, ".");
+            } else if (i == 1) {
+                sprintf(path, "..");
+            } else if (i == 2) {
+                sprintf(path, "hello");
+            } else {
+                sprintf(path, "hi%03d", i);
+            }
+
+            if (i == j) {
+                off = lfs_dir_tell(&lfs, &dir);
+                off >= 0 => true;
+            }
+
+            lfs_dir_read(&lfs, &dir, &info) => 1;
+            strcmp(path, info.name) => 0;
+        }
+        lfs_dir_read(&lfs, &dir, &info) => 0;
+        lfs_dir_close(&lfs, &dir) => 0;
+
+        lfs_dir_open(&lfs, &dir, "/") => 0;
+        lfs_dir_seek(&lfs, &dir, off) => 0;
+        for (int i = j; i < $MEDIUMSIZE; i++) {
+            if (i == 0) {
+                sprintf(path, ".");
+            } else if (i == 1) {
+                sprintf(path, "..");
+            } else if (i == 2) {
+                sprintf(path, "hello");
+            } else {
+                sprintf(path, "hi%03d", i);
+            }
+
+            lfs_dir_read(&lfs, &dir, &info) => 1;
+            strcmp(path, info.name) => 0;
+        }
+        lfs_dir_read(&lfs, &dir, &info) => 0;
+        lfs_dir_close(&lfs, &dir) => 0;
+    }
+
+    lfs_unmount(&lfs) => 0;
+TEST
+
 scripts/results.py