diff --git a/bd/lfs3_emubd.c b/bd/lfs3_emubd.c
index b627c163..f72d5fe9 100644
--- a/bd/lfs3_emubd.c
+++ b/bd/lfs3_emubd.c
@@ -166,23 +166,52 @@ static uint32_t lfs3_emubd_prng_(uint32_t *state) {
 
 int lfs3_emubd_createcfg(const struct lfs3_cfg *cfg, const char *path,
         const struct lfs3_emubd_cfg *bdcfg) {
-    LFS3_EMUBD_TRACE("lfs3_emubd_createcfg(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
-                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
+    LFS3_EMUBD_TRACE("lfs3_emubd_createcfg("
+                "%p {"
+                    ".context=%p, "
+                    ".read=%p, "
+                    ".prog=%p, "
+                    ".erase=%p, "
+                    ".sync=%p, "
+                    ".read_size=%"PRIu32", "
+                    ".prog_size=%"PRIu32", "
+                    ".block_size=%"PRIu32", "
+                    ".block_count=%"PRIu32"}, "
                 "\"%s\", "
-                "%p {.erase_value=%"PRId32", .erase_cycles=%"PRIu32", "
-                ".badblock_behavior=%"PRIu8", .power_cycles=%"PRIu32", "
-                ".powerloss_behavior=%"PRIu8", .powerloss_cb=%p, "
-                ".powerloss_data=%p, seed=%"PRIu32"})",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
-            path, (void*)bdcfg, bdcfg->erase_value, bdcfg->erase_cycles,
-            bdcfg->badblock_behavior, bdcfg->power_cycles,
-            bdcfg->powerloss_behavior, (void*)(uintptr_t)bdcfg->powerloss_cb,
-            bdcfg->powerloss_data, bdcfg->seed);
+                "%p {.erase_value=%"PRId32", "
+                    ".erase_cycles=%"PRIu32", "
+                    ".badblock_behavior=%"PRIu8", "
+                    ".power_cycles=%"PRIu32", "
+                    ".powerloss_behavior=%"PRIu8", "
+                    ".powerloss_cb=%p, "
+                    ".powerloss_data=%p, "
+                    ".seed=%"PRIu32", "
+                    ".read_sleep=%"PRIu64", "
+                    ".prog_sleep=%"PRIu64", "
+                    ".erase_sleep=%"PRIu64"})",
+            (void*)cfg,
+            cfg->context,
+            (void*)(uintptr_t)cfg->read,
+            (void*)(uintptr_t)cfg->prog,
+            (void*)(uintptr_t)cfg->erase,
+            (void*)(uintptr_t)cfg->sync,
+            cfg->read_size,
+            cfg->prog_size,
+            cfg->block_size,
+            cfg->block_count,
+            path,
+            (void*)bdcfg,
+            bdcfg->erase_value,
+            bdcfg->erase_cycles,
+            bdcfg->badblock_behavior,
+            bdcfg->power_cycles,
+            bdcfg->powerloss_behavior,
+            (void*)(uintptr_t)bdcfg->powerloss_cb,
+            bdcfg->powerloss_data,
+            bdcfg->seed,
+            bdcfg->read_sleep,
+            bdcfg->prog_sleep,
+            bdcfg->erase_sleep);
     lfs3_emubd_t *bd = cfg->context;
     bd->cfg = bdcfg;
 
@@ -229,7 +258,7 @@ int lfs3_emubd_createcfg(const struct lfs3_cfg *cfg, const char *path,
                 cfg->block_count * sizeof(lfs3_emubd_block_t*));
     }
 
-    if (bd->cfg->disk_path) {
+    if (path) {
         bd->disk = malloc(sizeof(lfs3_emubd_disk_t));
         if (!bd->disk) {
             err = LFS3_ERR_NOMEM;
@@ -240,11 +269,9 @@ int lfs3_emubd_createcfg(const struct lfs3_cfg *cfg, const char *path,
         bd->disk->scratch = NULL;
 
         #ifdef _WIN32
-        bd->disk->fd = open(bd->cfg->disk_path,
-                O_RDWR | O_CREAT | O_BINARY, 0666);
+        bd->disk->fd = open(path, O_RDWR | O_CREAT | O_BINARY, 0666);
         #else
-        bd->disk->fd = open(bd->cfg->disk_path,
-                O_RDWR | O_CREAT, 0666);
+        bd->disk->fd = open(path, O_RDWR | O_CREAT, 0666);
         #endif
         if (bd->disk->fd < 0) {
             err = -errno;
@@ -293,15 +320,28 @@ failed:;
 }
 
 int lfs3_emubd_create(const struct lfs3_cfg *cfg, const char *path) {
-    LFS3_EMUBD_TRACE("lfs3_emubd_create(%p {.context=%p, "
-                ".read=%p, .prog=%p, .erase=%p, .sync=%p, "
-                ".read_size=%"PRIu32", .prog_size=%"PRIu32", "
-                ".block_size=%"PRIu32", .block_count=%"PRIu32"}, "
+    LFS3_EMUBD_TRACE("lfs3_emubd_create("
+                "%p {"
+                    ".context=%p, "
+                    ".read=%p, "
+                    ".prog=%p, "
+                    ".erase=%p, "
+                    ".sync=%p, "
+                    ".read_size=%"PRIu32", "
+                    ".prog_size=%"PRIu32", "
+                    ".block_size=%"PRIu32", "
+                    ".block_count=%"PRIu32"}, "
                 "\"%s\")",
-            (void*)cfg, cfg->context,
-            (void*)(uintptr_t)cfg->read, (void*)(uintptr_t)cfg->prog,
-            (void*)(uintptr_t)cfg->erase, (void*)(uintptr_t)cfg->sync,
-            cfg->read_size, cfg->prog_size, cfg->block_size, cfg->block_count,
+            (void*)cfg,
+            cfg->context,
+            (void*)(uintptr_t)cfg->read,
+            (void*)(uintptr_t)cfg->prog,
+            (void*)(uintptr_t)cfg->erase,
+            (void*)(uintptr_t)cfg->sync,
+            cfg->read_size,
+            cfg->prog_size,
+            cfg->block_size,
+            cfg->block_count,
             path);
     static const struct lfs3_emubd_cfg defaults = {.erase_value=-1};
     int err = lfs3_emubd_createcfg(cfg, path, &defaults);
diff --git a/bd/lfs3_emubd.h b/bd/lfs3_emubd.h
index f9783948..f1b67bc7 100644
--- a/bd/lfs3_emubd.h
+++ b/bd/lfs3_emubd.h
@@ -100,11 +100,6 @@ struct lfs3_emubd_cfg {
     // not affect normal operation.
     uint32_t seed;
 
-    // Path to file to use as a mirror of the disk. This provides a way to view
-    // the current state of the block device, but does not eliminate the RAM
-    // requirement.
-    const char *disk_path;
-
     // Artificial delay in nanoseconds, there is no purpose for this other
     // than slowing down the simulation.
     lfs3_emubd_sleep_t read_sleep;
@@ -160,11 +155,10 @@ typedef struct lfs3_emubd {
 
 // Create an emulating block device using the geometry in lfs3_cfg
 //
-// If disk_path is provided, emubd will mirror the block device in the
-// file. Note this is a write-only mirror intended for introspection,
-// and does not eliminate the RAM requirement.
+// If path is provided, emubd will mirror the block device in the file.
+// This provides a way to view the current state of the block device,
+// but does not eliminate the RAM requirement.
 //
-// TODO wait, why do we have both disk_path and path here?
 int lfs3_emubd_create(const struct lfs3_cfg *cfg, const char *path);
 int lfs3_emubd_createcfg(const struct lfs3_cfg *cfg, const char *path,
         const struct lfs3_emubd_cfg *bdcfg);
diff --git a/bd/lfs3_kiwibd.c b/bd/lfs3_kiwibd.c
index e2b84b95..53dec9be 100644
--- a/bd/lfs3_kiwibd.c
+++ b/bd/lfs3_kiwibd.c
@@ -92,7 +92,6 @@ int lfs3_kiwibd_createcfg(const struct lfs3_cfg *cfg, const char *path,
                 "\"%s\", "
                 "%p {"
                     ".erase_value=%"PRId32", "
-                    ".disk_path=\"%s\", "
                     ".buffer=%p, "
                     ".read_sleep=%"PRIu64", "
                     ".prog_sleep=%"PRIu64", "
@@ -110,7 +109,6 @@ int lfs3_kiwibd_createcfg(const struct lfs3_cfg *cfg, const char *path,
             path,
             (void*)bdcfg,
             bdcfg->erase_value,
-            bdcfg->disk_path,
             bdcfg->buffer,
             bdcfg->read_sleep,
             bdcfg->prog_sleep,
@@ -122,35 +120,34 @@ int lfs3_kiwibd_createcfg(const struct lfs3_cfg *cfg, const char *path,
     bd->readed = 0;
     bd->proged = 0;
     bd->erased = 0;
-    if (bd->cfg->disk_path) {
-        bd->u.disk.fd = -1;
-        bd->u.disk.scratch = NULL;
+    bd->fd = -1;
+    if (path) {
+        bd->u.scratch = NULL;
     } else {
         bd->u.mem = NULL;
     }
     int err;
 
-    // if we have a disk_path, try to open the backing file
-    if (bd->cfg->disk_path) {
-        bd->u.disk.fd = open(bd->cfg->disk_path,
-                O_RDWR | O_CREAT, 0666);
-        if (bd->u.disk.fd < 0) {
+    // if we have a path, try to open the backing file
+    if (path) {
+        bd->fd = open(path, O_RDWR | O_CREAT, 0666);
+        if (bd->fd < 0) {
             err = -errno;
             goto failed;
         }
 
         // allocate a scratch buffer to help with zeroing/masking/etc
-        bd->u.disk.scratch = malloc(cfg->block_size);
-        if (!bd->u.disk.scratch) {
+        bd->u.scratch = malloc(cfg->block_size);
+        if (!bd->u.scratch) {
             err = LFS3_ERR_NOMEM;
             goto failed;
         }
 
         // zero for reproducibility
-        lfs3_kiwibd_memzero(cfg, bd->u.disk.scratch, cfg->block_size);
+        lfs3_kiwibd_memzero(cfg, bd->u.scratch, cfg->block_size);
         for (lfs3_block_t i = 0; i < cfg->block_count; i++) {
-            ssize_t res = write(bd->u.disk.fd,
-                    bd->u.disk.scratch,
+            ssize_t res = write(bd->fd,
+                    bd->u.scratch,
                     cfg->block_size);
             if (res < 0) {
                 err = -errno;
@@ -177,11 +174,9 @@ int lfs3_kiwibd_createcfg(const struct lfs3_cfg *cfg, const char *path,
 failed:;
     LFS3_KIWIBD_TRACE("lfs3_kiwibd_createcfg -> %d", err);
     // clean up memory
-    if (bd->cfg->disk_path) {
-        if (bd->u.disk.fd != -1) {
-            close(bd->u.disk.fd);
-        }
-        free(bd->u.disk.scratch);
+    if (bd->fd >= 0) {
+        close(bd->fd);
+        free(bd->u.scratch);
     } else {
         free(bd->u.mem);
     }
@@ -223,9 +218,9 @@ int lfs3_kiwibd_destroy(const struct lfs3_cfg *cfg) {
     lfs3_kiwibd_t *bd = cfg->context;
 
     // clean up memory
-    if (bd->cfg->disk_path) {
-        close(bd->u.disk.fd);
-        free(bd->u.disk.scratch);
+    if (bd->fd >= 0) {
+        close(bd->fd);
+        free(bd->u.scratch);
     } else {
         free(bd->u.mem);
     }
@@ -251,12 +246,12 @@ int lfs3_kiwibd_read(const struct lfs3_cfg *cfg, lfs3_block_t block,
     LFS3_ASSERT(off+size <= cfg->block_size);
 
     // read in file?
-    if (bd->cfg->disk_path) {
+    if (bd->fd >= 0) {
         lfs3_kiwibd_memerase(cfg,
-                bd->u.disk.scratch,
+                bd->u.scratch,
                 cfg->block_size);
 
-        off_t res = lseek(bd->u.disk.fd,
+        off_t res = lseek(bd->fd,
                 (off_t)block*cfg->block_size + (off_t)off,
                 SEEK_SET);
         if (res < 0) {
@@ -265,7 +260,7 @@ int lfs3_kiwibd_read(const struct lfs3_cfg *cfg, lfs3_block_t block,
             return err;
         }
 
-        ssize_t res_ = read(bd->u.disk.fd, buffer, size);
+        ssize_t res_ = read(bd->fd, buffer, size);
         if (res_ < 0) {
             int err = -errno;
             LFS3_KIWIBD_TRACE("lfs3_kiwibd_read -> %d", err);
@@ -312,10 +307,10 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
     LFS3_ASSERT(off+size <= cfg->block_size);
 
     // prog in file?
-    if (bd->cfg->disk_path) {
+    if (bd->fd >= 0) {
         // were we erased properly?
         if (bd->cfg->erase_value >= 0) {
-            off_t res = lseek(bd->u.disk.fd,
+            off_t res = lseek(bd->fd,
                     (off_t)block*cfg->block_size + (off_t)off,
                     SEEK_SET);
             if (res < 0) {
@@ -324,7 +319,7 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
                 return err;
             }
 
-            ssize_t res_ = read(bd->u.disk.fd, bd->u.disk.scratch, size);
+            ssize_t res_ = read(bd->fd, bd->u.scratch, size);
             if (res_ < 0) {
                 int err = -errno;
                 LFS3_KIWIBD_TRACE("lfs3_kiwibd_prog -> %d", err);
@@ -332,13 +327,13 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
             }
 
             for (lfs3_off_t i = 0; i < size; i++) {
-                LFS3_ASSERT(bd->u.disk.scratch[i] == bd->cfg->erase_value);
+                LFS3_ASSERT(bd->u.scratch[i] == bd->cfg->erase_value);
             }
         }
 
         // masking progs?
         if (bd->cfg->erase_value == -2) {
-            off_t res = lseek(bd->u.disk.fd,
+            off_t res = lseek(bd->fd,
                     (off_t)block*cfg->block_size + (off_t)off,
                     SEEK_SET);
             if (res < 0) {
@@ -347,16 +342,16 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
                 return err;
             }
 
-            ssize_t res_ = read(bd->u.disk.fd, bd->u.disk.scratch, size);
+            ssize_t res_ = read(bd->fd, bd->u.scratch, size);
             if (res_ < 0) {
                 int err = -errno;
                 LFS3_KIWIBD_TRACE("lfs3_kiwibd_prog -> %d", err);
                 return err;
             }
 
-            lfs3_kiwibd_memprog(cfg, bd->u.disk.scratch, buffer, size);
+            lfs3_kiwibd_memprog(cfg, bd->u.scratch, buffer, size);
 
-            res = lseek(bd->u.disk.fd,
+            res = lseek(bd->fd,
                     (off_t)block*cfg->block_size + (off_t)off,
                     SEEK_SET);
             if (res < 0) {
@@ -365,7 +360,7 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
                 return err;
             }
 
-            res_ = write(bd->u.disk.fd, bd->u.disk.scratch, size);
+            res_ = write(bd->fd, bd->u.scratch, size);
             if (res_ < 0) {
                 int err = -errno;
                 LFS3_KIWIBD_TRACE("lfs3_kiwibd_prog -> %d", err);
@@ -374,7 +369,7 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
 
         // normal progs?
         } else {
-            off_t res = lseek(bd->u.disk.fd,
+            off_t res = lseek(bd->fd,
                     (off_t)block*cfg->block_size + (off_t)off,
                     SEEK_SET);
             if (res < 0) {
@@ -383,7 +378,7 @@ int lfs3_kiwibd_prog(const struct lfs3_cfg *cfg, lfs3_block_t block,
                 return err;
             }
 
-            ssize_t res_ = write(bd->u.disk.fd, buffer, size);
+            ssize_t res_ = write(bd->fd, buffer, size);
             if (res_ < 0) {
                 int err = -errno;
                 LFS3_KIWIBD_TRACE("lfs3_kiwibd_prog -> %d", err);
@@ -437,8 +432,8 @@ int lfs3_kiwibd_erase(const struct lfs3_cfg *cfg, lfs3_block_t block) {
     // emulate an erase value?
     if (bd->cfg->erase_value != -1) {
         // erase in file?
-        if (bd->cfg->disk_path) {
-            off_t res = lseek(bd->u.disk.fd,
+        if (bd->fd >= 0) {
+            off_t res = lseek(bd->fd,
                     (off_t)block*cfg->block_size,
                     SEEK_SET);
             if (res < 0) {
@@ -448,11 +443,11 @@ int lfs3_kiwibd_erase(const struct lfs3_cfg *cfg, lfs3_block_t block) {
             }
 
             lfs3_kiwibd_memerase(cfg,
-                    bd->u.disk.scratch,
+                    bd->u.scratch,
                     cfg->block_size);
 
-            ssize_t res_ = write(bd->u.disk.fd,
-                    bd->u.disk.scratch,
+            ssize_t res_ = write(bd->fd,
+                    bd->u.scratch,
                     cfg->block_size);
             if (res_ < 0) {
                 int err = -errno;
diff --git a/bd/lfs3_kiwibd.h b/bd/lfs3_kiwibd.h
index 2e182fa9..0cd36728 100644
--- a/bd/lfs3_kiwibd.h
+++ b/bd/lfs3_kiwibd.h
@@ -39,10 +39,6 @@ struct lfs3_kiwibd_cfg {
     // does _not_ rely on this!).
     int32_t erase_value;
 
-    // Path to file to back the block device. If provided kiwibd uses this
-    // instead of RAM, allowing emulation of block devices > available RAM.
-    const char *disk_path;
-
     // Optional statically allocated buffer for the block device. Ignored
     // if disk_path is provided.
     void *buffer;
@@ -63,11 +59,9 @@ struct lfs3_kiwibd_cfg {
 // kiwibd state
 typedef struct lfs3_kiwibd {
     // backing disk
+    int fd;
     union {
-        struct {
-            int fd;
-            uint8_t *scratch;
-        } disk;
+        uint8_t *scratch;
         uint8_t *mem;
     } u;
 
@@ -84,10 +78,9 @@ typedef struct lfs3_kiwibd {
 
 // Create a kiwibd using the geometry in lfs3_cfg
 //
-// If disk_path is provided, it will be used to back the kiwibd,
-// otherwise kiwibd will try to use RAM.
+// If path is provided, kiwibd will use the file to back the block
+// device, allowing emulation of block devices > available RAM.
 //
-// TODO wait, why do we have both disk_path and path here?
 int lfs3_kiwibd_create(const struct lfs3_cfg *cfg, const char *path);
 int lfs3_kiwibd_createcfg(const struct lfs3_cfg *cfg, const char *path,
         const struct lfs3_kiwibd_cfg *bdcfg);
diff --git a/runners/bench_runner.c b/runners/bench_runner.c
index 7805e333..50bc8be9 100644
--- a/runners/bench_runner.c
+++ b/runners/bench_runner.c
@@ -1355,7 +1355,6 @@ void perm_run(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = bench_disk_path,
         .read_sleep         = bench_read_sleep,
         .prog_sleep         = bench_prog_sleep,
         .erase_sleep        = bench_erase_sleep,
diff --git a/runners/test_runner.c b/runners/test_runner.c
index 3b948d2d..ae2d4d52 100644
--- a/runners/test_runner.c
+++ b/runners/test_runner.c
@@ -1319,7 +1319,6 @@ static void run_powerloss_none(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = test_disk_path,
         .read_sleep         = test_read_sleep,
         .prog_sleep         = test_prog_sleep,
         .erase_sleep        = test_erase_sleep,
@@ -1380,7 +1379,6 @@ static void run_powerloss_linear(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = test_disk_path,
         .read_sleep         = test_read_sleep,
         .prog_sleep         = test_prog_sleep,
         .erase_sleep        = test_erase_sleep,
@@ -1457,7 +1455,6 @@ static void run_powerloss_log(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = test_disk_path,
         .read_sleep         = test_read_sleep,
         .prog_sleep         = test_prog_sleep,
         .erase_sleep        = test_erase_sleep,
@@ -1534,7 +1531,6 @@ static void run_powerloss_cycles(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = test_disk_path,
         .read_sleep         = test_read_sleep,
         .prog_sleep         = test_prog_sleep,
         .erase_sleep        = test_erase_sleep,
@@ -1709,7 +1705,6 @@ static void run_powerloss_exhaustive(
     };
 
     struct lfs3_emubd_cfg bdcfg = {
-        .disk_path          = test_disk_path,
         .read_sleep         = test_read_sleep,
         .prog_sleep         = test_prog_sleep,
         .erase_sleep        = test_erase_sleep,