disk: update epoc.txt and vere.txt atomically (#669)

Fixes #640
urbit · Jul 24, 2024 · e388128 · e388128
2 parents 692466f + 8f1bf10
commit e388128
Showing 1 changed file with 64 additions and 17 deletions.
diff --git a/pkg/vere/disk.c b/pkg/vere/disk.c
@@ -1123,18 +1123,39 @@ u3_disk_epoc_zero(u3_disk* log_u)
   }
 
   //  create epoch version file, overwriting any existing file
+  c3_c epi_c[8193];
   c3_c epv_c[8193];
+  snprintf(epi_c, sizeof(epv_c), "%s/epoc.tmp", epo_c);
   snprintf(epv_c, sizeof(epv_c), "%s/epoc.txt", epo_c);
-  FILE* epv_f = fopen(epv_c, "w");  // XX errors
-  fprintf(epv_f, "%d", U3E_VERLAT);
-  fclose(epv_f);
+  FILE* epv_f = fopen(epi_c, "w");  // XX errors
+
+  if (  !epv_f
+     || (0 > fprintf(epv_f, "%d", U3E_VERLAT))
+     || fflush(epv_f)
+     || (-1 == c3_sync(fileno(epv_f)))
+     || fclose(epv_f)
+     || (-1 == rename(epi_c, epv_c)) )
+  {
+    fprintf(stderr, "disk: write epoc.txt failed %s\r\n", strerror(errno));
+    goto fail3;
+  }
 
   //  create binary version file, overwriting any existing file
+  c3_c bii_c[8193];
   c3_c biv_c[8193];
-  snprintf(biv_c, sizeof(biv_c), "%s/vere.txt", epo_c);
-  FILE* biv_f = fopen(biv_c, "w");  //  XX errors
-  fprintf(biv_f, URBIT_VERSION);    //  XX append a sentinel for auto-rollover?
-  fclose(biv_f);
+  snprintf(bii_c, sizeof(biv_c), "%s/vere.tmp", epo_c);
+  snprintf(biv_c, sizeof(epv_c), "%s/vere.txt", epo_c);
+  FILE* biv_f = fopen(bii_c, "w");
+  if (  !biv_f
+     || (0 > fprintf(biv_f, URBIT_VERSION))
+     || fflush(biv_f)
+     || (-1 == c3_sync(fileno(biv_f)))
+     || fclose(biv_f)
+     || (-1 == rename(bii_c, biv_c)) )
+  {
+    fprintf(stderr, "disk: write vere.txt failed %s\r\n", strerror(errno));
+    goto fail3;
+  }
 
   if ( -1 == c3_sync(epo_i) ) {  //  XX fdatasync on linux?
     fprintf(stderr, "disk: sync epoch dir 0i0 failed: %s\r\n", strerror(errno));
@@ -1205,18 +1226,44 @@ _disk_epoc_roll(u3_disk* log_u, c3_d epo_d)
   }
 
   //  create epoch version file, overwriting any existing file
+  c3_c epi_c[8193];
   c3_c epv_c[8193];
+  snprintf(epi_c, sizeof(epv_c), "%s/epoc.tmp", epo_c);
   snprintf(epv_c, sizeof(epv_c), "%s/epoc.txt", epo_c);
-  FILE* epv_f = fopen(epv_c, "w");  // XX errors
-  fprintf(epv_f, "%d", U3E_VERLAT);
-  fclose(epv_f);
+  FILE* epv_f = fopen(epi_c, "w");
+
+  if (  !epv_f
+     || (0 > fprintf(epv_f, "%d", U3E_VERLAT))
+     || fflush(epv_f)
+     || (-1 == c3_sync(fileno(epv_f)))
+     || fclose(epv_f)
+     || (-1 == rename(epi_c, epv_c)) )
+  {
+    fprintf(stderr, "disk: write epoc.txt failed %s\r\n", strerror(errno));
+    goto fail3;
+  }
 
   //  create binary version file, overwriting any existing file
+  c3_c bii_c[8193];
   c3_c biv_c[8193];
-  snprintf(biv_c, sizeof(biv_c), "%s/vere.txt", epo_c);
-  FILE* biv_f = fopen(biv_c, "w");  //  XX errors
-  fprintf(biv_f, URBIT_VERSION);
-  fclose(biv_f);
+  snprintf(bii_c, sizeof(biv_c), "%s/vere.tmp", epo_c);
+  snprintf(biv_c, sizeof(epv_c), "%s/vere.txt", epo_c);
+  FILE* biv_f = fopen(bii_c, "w");
+  if (  !biv_f
+     || (0 > fprintf(biv_f, URBIT_VERSION))
+     || fflush(biv_f)
+     || (-1 == c3_sync(fileno(biv_f)))
+     || fclose(biv_f)
+     || (-1 == rename(bii_c, biv_c)) )
+  {
+    fprintf(stderr, "disk: write vere.txt failed %s\r\n", strerror(errno));
+    goto fail3;
+  }
+
+  if ( -1 == c3_sync(epo_i) ) {  //  XX fdatasync on linux?
+    fprintf(stderr, "disk: sync epoch dir 0i0 failed: %s\r\n", strerror(errno));
+    goto fail3;
+  }
 
   //  get metadata from old log
   c3_d     who_d[2];
@@ -1707,9 +1754,9 @@ _disk_epoc_load(u3_disk* log_u, c3_d lat_d)
       return _epoc_gone;
     }
 
-    if (  (1 != sscanf(ver_c, "%" SCNu32 "%n", &ver_w, &car_i))
-       && (0 < car_i)
-       && ('\0' == *(ver_c + car_i)) )
+    if ( !(  (1 == sscanf(ver_c, "%" SCNu32 "%n", &ver_w, &car_i))
+          && (0 < car_i)
+          && ('\0' == *(ver_c + car_i)) ) )
     {
       fprintf(stderr, "disk: failed to parse epoch version: '%s'\r\n", ver_c);
       return _epoc_fail;