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.

Makefile

@@ -55,7 +55,6 @@ test: \
 	test_attrs \
 	test_move \
 	test_orphan \
-	test_relocations \
 	test_corrupt
 	@rm test.c
 test_%: tests/test_%.sh

lfs.c

@@ -2068,10 +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) {
@@ -2084,6 +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;
         }
     }
 
@@ -2107,6 +2113,8 @@ int lfs_dir_rewind(lfs_t *lfs, lfs_dir_t *dir) {
         return err;
     }
 
+    dir->m.pair[0] = dir->head[0];
+    dir->m.pair[1] = dir->head[1];
     dir->id = 0;
     dir->pos = 0;
     LFS_TRACE("lfs_dir_rewind -> %d", 0);
@@ -3889,12 +3897,6 @@ static int lfs_fs_relocate(lfs_t *lfs,
             d->m.pair[0] = newpair[0];
             d->m.pair[1] = newpair[1];
         }
-
-        if (d->type == LFS_TYPE_DIR &&
-                lfs_pair_cmp(oldpair, ((lfs_dir_t*)d)->head) == 0) {
-            ((lfs_dir_t*)d)->head[0] = newpair[0];
-            ((lfs_dir_t*)d)->head[1] = newpair[1];
-        }
     }
 
     // find parent

tests/test_relocations.sh

@@ -1,88 +0,0 @@
-#!/bin/bash
-set -eu
-export TEST_FILE=$0
-trap 'export TEST_LINE=$LINENO' DEBUG
-
-ITERATIONS=20
-COUNT=10
-
-echo "=== Relocation tests ==="
-rm -rf blocks
-scripts/test.py << TEST
-    lfs_format(&lfs, &cfg) => 0;
-    // fill up filesystem so only ~16 blocks are left
-    lfs_mount(&lfs, &cfg) => 0;
-    lfs_file_open(&lfs, &file, "padding", LFS_O_CREAT | LFS_O_WRONLY) => 0;
-    memset(buffer, 0, 512);
-    while (LFS_BLOCK_COUNT - lfs_fs_size(&lfs) > 16) {
-        lfs_file_write(&lfs, &file, buffer, 512) => 512;
-    }
-    lfs_file_close(&lfs, &file) => 0;
-    // make a child dir to use in bounded space
-    lfs_mkdir(&lfs, "child") => 0;
-    lfs_unmount(&lfs) => 0;
-TEST
-
-echo "--- Outdated head test ---"
-scripts/test.py << TEST
-    lfs_mount(&lfs, &cfg) => 0;
-    for (int j = 0; j < $ITERATIONS; j++) {
-        for (int i = 0; i < $COUNT; i++) {
-            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
-            lfs_file_open(&lfs, &file, path, LFS_O_CREAT | LFS_O_WRONLY) => 0;
-            lfs_file_close(&lfs, &file) => 0;
-        }
-
-        lfs_dir_open(&lfs, &dir, "child") => 0;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        for (int i = 0; i < $COUNT; i++) {
-            sprintf(path, "test%03d_loooooooooooooooooong_name", i);
-            lfs_dir_read(&lfs, &dir, &info) => 1;
-            strcmp(info.name, path) => 0;
-            info.size => 0;
-
-            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
-            lfs_file_open(&lfs, &file, path, LFS_O_WRONLY) => 0;
-            lfs_file_write(&lfs, &file, "hi", 2) => 2;
-            lfs_file_close(&lfs, &file) => 0;
-        }
-        lfs_dir_read(&lfs, &dir, &info) => 0;
-
-        lfs_dir_rewind(&lfs, &dir) => 0;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        for (int i = 0; i < $COUNT; i++) {
-            sprintf(path, "test%03d_loooooooooooooooooong_name", i);
-            lfs_dir_read(&lfs, &dir, &info) => 1;
-            strcmp(info.name, path) => 0;
-            info.size => 2;
-
-            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
-            lfs_file_open(&lfs, &file, path, LFS_O_WRONLY) => 0;
-            lfs_file_write(&lfs, &file, "hi", 2) => 2;
-            lfs_file_close(&lfs, &file) => 0;
-        }
-        lfs_dir_read(&lfs, &dir, &info) => 0;
-
-        lfs_dir_rewind(&lfs, &dir) => 0;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        lfs_dir_read(&lfs, &dir, &info) => 1;
-        for (int i = 0; i < $COUNT; i++) {
-            sprintf(path, "test%03d_loooooooooooooooooong_name", i);
-            lfs_dir_read(&lfs, &dir, &info) => 1;
-            strcmp(info.name, path) => 0;
-            info.size => 2;
-        }
-        lfs_dir_read(&lfs, &dir, &info) => 0;
-        lfs_dir_close(&lfs, &dir) => 0;
-
-        for (int i = 0; i < $COUNT; i++) {
-            sprintf(path, "child/test%03d_loooooooooooooooooong_name", i);
-            lfs_remove(&lfs, path) => 0;
-        }
-    }
-    lfs_unmount(&lfs) => 0;
-TEST
-
-scripts/results.py

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