diff --git a/lfs.c b/lfs.c
index 48522e1d..6bba30c0 100644
--- a/lfs.c
+++ b/lfs.c
@@ -11331,6 +11331,13 @@ int lfsr_file_opencfg(lfs_t *lfs, lfsr_file_t *file,
     LFS_ASSERT(!lfsr_o_isrdonly(flags) || !lfsr_o_iscreat(flags));
     LFS_ASSERT(!lfsr_o_isrdonly(flags) || !lfsr_o_isexcl(flags));
     LFS_ASSERT(!lfsr_o_isrdonly(flags) || !lfsr_o_istrunc(flags));
+    // these flags are incompatible
+    LFS_ASSERT(lfsr_o_isrdonly(flags)
+            || !lfsr_o_issync(flags)
+            || !lfsr_o_isdesync(flags));
+    LFS_ASSERT(lfsr_o_isrdonly(flags)
+            || !lfsr_o_issync(lfs->flags)
+            || !lfsr_o_isdesync(flags));
     for (lfs_size_t i = 0; i < cfg->attr_count; i++) {
         // these flags require a writable attr
         LFS_ASSERT(!lfsr_o_isrdonly(cfg->attrs[i].flags)
@@ -11461,9 +11468,8 @@ int lfsr_file_opencfg(lfs_t *lfs, lfsr_file_t *file,
     lfsr_omdir_open(lfs, &file->b.o);
 
     // sync if requested
-    if (!lfsr_o_isrdonly(file->b.o.flags)
-            && lfsr_o_issync(file->b.o.flags)
-            && lfsr_o_isunsync(file->b.o.flags)) {
+    if (lfsr_o_issync(file->b.o.flags)
+            && !lfsr_o_isrdonly(file->b.o.flags)) {
         err = lfsr_file_sync(lfs, file);
         if (err) {
             lfsr_omdir_close(lfs, &file->b.o);
@@ -12946,6 +12952,8 @@ failed:;
 int lfsr_file_desync(lfs_t *lfs, lfsr_file_t *file) {
     (void)lfs;
     LFS_ASSERT(lfsr_omdir_isopen(lfs, &file->b.o));
+    // desyncing LFS_O_SYNC files is not allowed
+    LFS_ASSERT(!lfsr_o_issync(file->b.o.flags));
 
     // mark as desynced
     file->b.o.flags |= LFS_O_DESYNC;
diff --git a/tests/test_fsync.toml b/tests/test_fsync.toml
index 7669afd5..1bd6fd67 100644
--- a/tests/test_fsync.toml
+++ b/tests/test_fsync.toml
@@ -2480,7 +2480,7 @@ code = '''
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
 # SYNC=3 => sync via LFS_M_SYNC
-defines.SYNC = [2, 3]
+defines.SYNC = [2]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -2496,7 +2496,7 @@ code = '''
             CFG) => 0;
 
     // a - desynced writer
-    // b - writer
+    // b - synced writer
     // c - reader kept open, recvs updates from a
     // d - reader kept closed, checks disk state
     lfsr_file_t a;
@@ -2504,44 +2504,40 @@ code = '''
     lfsr_file_t c;
     lfsr_file_t d;
     uint8_t rbuf[256];
-    // LFS_O_SYNC/LFS_M_SYNC should immediately create the file
     lfsr_file_open(&lfs, &a, "jello",
             LFS_O_WRONLY
                 | LFS_O_CREAT
                 | LFS_O_EXCL
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
                 | LFS_O_DESYNC) => 0;
-    struct lfs_info info;
-    lfsr_stat(&lfs, "jello", &info) => 0;
-    assert(strcmp(info.name, "jello") == 0);
-    assert(info.type == LFS_TYPE_REG);
-    assert(info.size == 0);
-    // create the other files
     lfsr_file_open(&lfs, &b, "jello",
             LFS_O_WRONLY
+                | LFS_O_CREAT
+                | LFS_O_EXCL
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
                 | ((SYNC == 2) ? LFS_O_SYNC : 0)) => 0;
     lfsr_file_open(&lfs, &c, "jello", LFS_O_RDONLY) => 0;
 
-    // write to b
-    lfsr_file_write(&lfs, &b, "hello!", strlen("hello!"))
+    // write to a
+    lfsr_file_write(&lfs, &a, "hello!", strlen("hello!"))
             => strlen("hello!");
+    // write to b
+    lfsr_file_write(&lfs, &b, "bonjour!", strlen("bonjour!"))
+            => strlen("bonjour!");
 
     // our write should show up in c
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
     // sync a
     lfsr_file_sync(&lfs, &a) => 0;
 
-    // c should still have b, this may be surprising, but the implicit
-    // sync in open+O_CREAT clears the desync flag
+    // c should revert to a's contents
     lfsr_file_rewind(&lfs, &c) => 0;
     lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
     assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
@@ -2551,17 +2547,44 @@ code = '''
     assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // reopen with LFS_O_TRUNC
+    // reopen a with LFS_O_TRUNC
     lfsr_file_close(&lfs, &a) => 0;
     lfsr_file_open(&lfs, &a, "jello",
             LFS_O_WRONLY
                 | LFS_O_TRUNC
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
                 | LFS_O_DESYNC) => 0;
 
+    // c should still have a's contents
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    // and on disk
+    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    lfsr_file_close(&lfs, &d) => 0;
+
+    // rewrite b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_write(&lfs, &b, "ohayo!", strlen("ohayo!"))
+            => strlen("ohayo!");
+
     // should immediately show up in c
     lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
+    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    // and on disk
+    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
+    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    lfsr_file_close(&lfs, &d) => 0;
+
+    // sync a
+    lfsr_file_sync(&lfs, &a) => 0;
+
+    // c should revert to a's contents
+    lfsr_file_rewind(&lfs, &c) => 0;
     lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => 0;
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
@@ -2573,86 +2596,18 @@ code = '''
     lfsr_file_open(&lfs, &a, "jello",
             LFS_O_WRONLY
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
                 | LFS_O_DESYNC) => 0;
-    lfsr_file_write(&lfs, &a, "bonjour!", strlen("bonjour!"))
-            => strlen("bonjour!");
-
-    // should immediately show up in c
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // sync b
-    lfsr_file_sync(&lfs, &b) => 0;
-
-    // should still have a
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // reopen a
-    lfsr_file_close(&lfs, &a) => 0;
-    lfsr_file_open(&lfs, &a, "jello",
-            LFS_O_WRONLY
-                | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
-                | LFS_O_DESYNC) => 0;
-    // rewrite b
-    lfsr_file_rewind(&lfs, &b) => 0;
-    lfsr_file_write(&lfs, &b, "ohayo!", strlen("ohayo!"))
-            => strlen("ohayo!");
-
-    // should immediately show up in c
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
-    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
-    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // sync a
-    lfsr_file_sync(&lfs, &a) => 0;
-
-    // c should revert to a's contents
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
-    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // rewrite a
-    lfsr_file_rewind(&lfs, &a) => 0;
     lfsr_file_write(&lfs, &a, "zdrasti!", strlen("zdrasti!"))
             => strlen("zdrasti!");
 
-    // should immediately show up in c
+    // c should still have a's contents
     lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
-    assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => 0;
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
-    assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => 0;
     lfsr_file_close(&lfs, &d) => 0;
 
-    // desync a
-    lfsr_file_desync(&lfs, &a) => 0;
     // rewrite b
     lfsr_file_rewind(&lfs, &b) => 0;
     lfsr_file_write(&lfs, &b, "annyeong!", strlen("annyeong!"))
@@ -2681,9 +2636,12 @@ code = '''
     assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // lets rewrite a one last time
+    // lets rewrite a and b one last time
     lfsr_file_rewind(&lfs, &a) => 0;
-    lfsr_file_write(&lfs, &a, "czesc!", strlen("czesc!"))
+    lfsr_file_write(&lfs, &a, "moshimoshi!", strlen("moshimoshi!"))
+            => strlen("moshimoshi!");
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_write(&lfs, &b, "czesc!", strlen("czesc!"))
             => strlen("czesc!");
 
     // should immediately show up in c
@@ -2700,7 +2658,7 @@ code = '''
     lfsr_file_close(&lfs, &a) => 0;
     lfsr_file_close(&lfs, &b) => 0;
 
-    // should still have a
+    // should still have b
     lfsr_file_rewind(&lfs, &c) => 0;
     lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!i!");
     assert(memcmp(rbuf, "czesc!i!", strlen("czesc!i!")) == 0);
@@ -3063,7 +3021,7 @@ defines.R = 4
 # SYNC=0 => no sync, readers not updated
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
-defines.SYNC = [0, 1, 2]
+defines.SYNC = [0, 1]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -3156,7 +3114,7 @@ defines.R = 4
 # SYNC=0 => no sync, readers not updated
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
-defines.SYNC = [0, 1, 2]
+defines.SYNC = [0, 1]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -3451,7 +3409,7 @@ defines.RW = 4
 # SYNC=0 => no sync, readers not updated
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
-defines.SYNC = [0, 1, 2]
+defines.SYNC = [0, 1]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -3559,7 +3517,7 @@ defines.RW = 4
 # SYNC=0 => no sync, readers not updated
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
-defines.SYNC = [0, 1, 2]
+defines.SYNC = [0, 1]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -4344,7 +4302,7 @@ code = '''
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
 # SYNC=3 => sync via LFS_M_SYNC
-defines.SYNC = [2, 3]
+defines.SYNC = [2]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
@@ -4360,7 +4318,7 @@ code = '''
             CFG) => 0;
 
     // a - desynced writer
-    // b - writer
+    // b - synced writer
     // c - reader kept open, recvs updates from a
     // d - reader kept closed, checks disk state
     lfsr_file_t a;
@@ -4368,66 +4326,42 @@ code = '''
     lfsr_file_t c;
     lfsr_file_t d;
     uint8_t rbuf[256];
-    // LFS_O_SYNC/LFS_M_SYNC should immediately create the file
     lfsr_file_open(&lfs, &a, "jello",
             LFS_O_WRONLY
                 | LFS_O_CREAT
                 | LFS_O_EXCL
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
                 | LFS_O_DESYNC) => 0;
-    struct lfs_info info;
-    lfsr_stat(&lfs, "jello", &info) => 0;
-    assert(strcmp(info.name, "jello") == 0);
-    assert(info.type == LFS_TYPE_REG);
-    assert(info.size == 0);
-    // create the other files
     lfsr_file_open(&lfs, &b, "jello",
             LFS_O_WRONLY
+                | LFS_O_CREAT
+                | LFS_O_EXCL
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
                 | ((SYNC == 2) ? LFS_O_SYNC : 0)) => 0;
     lfsr_file_open(&lfs, &c, "jello", LFS_O_RDONLY) => 0;
 
-    // write to b
-    lfsr_file_write(&lfs, &b, "hello!", strlen("hello!"))
+    // write to a
+    lfsr_file_write(&lfs, &a, "hello!", strlen("hello!"))
             => strlen("hello!");
-
-    // our write should show up in c
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // sync a
-    lfsr_file_sync(&lfs, &a) => 0;
-
-    // c should still have b, this may be surprising, but the implicit
-    // sync in open+O_CREAT clears the desync flag
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // reopen a
-    lfsr_file_close(&lfs, &a) => 0;
-    lfsr_file_open(&lfs, &a, "jello",
-            LFS_O_WRONLY
-                | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
-                | LFS_O_DESYNC) => 0;
-    // rewrite b
-    lfsr_file_rewind(&lfs, &b) => 0;
+    // write to b
     lfsr_file_write(&lfs, &b, "bonjour!", strlen("bonjour!"))
             => strlen("bonjour!");
 
-    // should immediately show up in c
+    // our write should show up in c
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // and on disk
+    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    lfsr_file_close(&lfs, &d) => 0;
+
+    // resync a
+    lfsr_file_resync(&lfs, &a) => 0;
+    // sync a
+    lfsr_file_sync(&lfs, &a) => 0;
+
+    // c should still have b's contents
     lfsr_file_rewind(&lfs, &c) => 0;
     lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
     assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
@@ -4437,26 +4371,24 @@ code = '''
     assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // sync a
-    lfsr_file_sync(&lfs, &a) => 0;
-
-    // c should revert to a's contents
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
-    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // reopen a
+    // reopen a with LFS_O_TRUNC
     lfsr_file_close(&lfs, &a) => 0;
     lfsr_file_open(&lfs, &a, "jello",
             LFS_O_WRONLY
+                | LFS_O_TRUNC
                 | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
-                | ((SYNC == 2) ? LFS_O_SYNC : 0)
                 | LFS_O_DESYNC) => 0;
+
+    // c should still have b's contents
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // and on disk
+    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    lfsr_file_close(&lfs, &d) => 0;
+
     // rewrite b
     lfsr_file_rewind(&lfs, &b) => 0;
     lfsr_file_write(&lfs, &b, "ohayo!", strlen("ohayo!"))
@@ -4464,12 +4396,12 @@ code = '''
 
     // should immediately show up in c
     lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
     // resync a
@@ -4477,49 +4409,38 @@ code = '''
     // sync a
     lfsr_file_sync(&lfs, &a) => 0;
 
-    // c should still show b's changes
+    // c should still have b's contents
     lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // desync a
-    lfsr_file_desync(&lfs, &a) => 0;
-    // rewrite b
-    lfsr_file_rewind(&lfs, &b) => 0;
-    lfsr_file_write(&lfs, &b, "zdrasti!", strlen("zdrasti!"))
+    // reopen LFS_O_WRONLY and rewrite a
+    lfsr_file_close(&lfs, &a) => 0;
+    lfsr_file_open(&lfs, &a, "jello",
+            LFS_O_WRONLY
+                | ((FLUSH == 2) ? LFS_O_FLUSH : 0)
+                | LFS_O_DESYNC) => 0;
+    lfsr_file_write(&lfs, &a, "zdrasti!", strlen("zdrasti!"))
             => strlen("zdrasti!");
 
-    // should immediately show up in c
+    // c should still have b's contents
     lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
-    assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     // and on disk
     lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
-    assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
+    assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // sync a
-    lfsr_file_sync(&lfs, &a) => 0;
-
-    // c should revert to a's contents
-    lfsr_file_rewind(&lfs, &c) => 0;
-    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
-    // and on disk
-    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
-    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
-    assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
-    lfsr_file_close(&lfs, &d) => 0;
-
-    // rewrite a
-    lfsr_file_rewind(&lfs, &a) => 0;
-    lfsr_file_write(&lfs, &a, "annyeong!", strlen("annyeong!"))
+    // rewrite b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_write(&lfs, &b, "annyeong!", strlen("annyeong!"))
             => strlen("annyeong!");
 
     // should immediately show up in c
@@ -4532,14 +4453,32 @@ code = '''
     assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // desync b
-    lfsr_file_desync(&lfs, &b) => 0;
-    // resync b
-    lfsr_file_resync(&lfs, &b) => 0;
-    // rewrite b
+    // resync a
+    lfsr_file_resync(&lfs, &a) => 0;
+    // sync a
+    lfsr_file_sync(&lfs, &a) => 0;
+
+    // c should still have b's contents
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("annyeong!");
+    assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
+    // and on disk
+    lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("annyeong!");
+    assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
+    lfsr_file_close(&lfs, &d) => 0;
+
+    // desync a
+    lfsr_file_desync(&lfs, &a) => 0;
+    // lets rewrite a and b one last time
+    lfsr_file_rewind(&lfs, &a) => 0;
+    lfsr_file_write(&lfs, &a, "moshimoshi!", strlen("moshimoshi!"))
+            => strlen("moshimoshi!");
     lfsr_file_rewind(&lfs, &b) => 0;
     lfsr_file_write(&lfs, &b, "czesc!", strlen("czesc!"))
             => strlen("czesc!");
+    // resync a
+    lfsr_file_resync(&lfs, &a) => 0;
 
     // should immediately show up in c
     lfsr_file_rewind(&lfs, &c) => 0;
@@ -4551,12 +4490,11 @@ code = '''
     assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
     lfsr_file_close(&lfs, &d) => 0;
 
-    // close b
-    lfsr_file_close(&lfs, &b) => 0;
-    // close a
+    // close a and b
     lfsr_file_close(&lfs, &a) => 0;
+    lfsr_file_close(&lfs, &b) => 0;
 
-    // c should still show b's changes
+    // should still have b
     lfsr_file_rewind(&lfs, &c) => 0;
     lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!ng!");
     assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
@@ -4900,7 +4838,7 @@ defines.R = 4
 # SYNC=0 => no sync, readers not updated
 # SYNC=1 => sync via lfsr_file_sync
 # SYNC=2 => sync via LFS_O_SYNC
-defines.SYNC = [0, 1, 2]
+defines.SYNC = [0, 1]
 # FLUSH=0 => no flush
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH