Second part of the format-upgrade support: ensure snapshots are there

 We don't want to install compiled dbs without having a snapshot of
their source set, so whenever we test that the compiled db is up to
date, we also test that a snapshot is present. This is important
because we will auto-cleanup unused snapshots after installation.

1 files changed, 34 insertions, 0 deletions

diff --git a/src/repo/s6rc_repo_setuptodate.c b/src/repo/s6rc_repo_setuptodate.c
index f01143f..cfc6731 100644
--- a/src/repo/s6rc_repo_setuptodate.c
+++ b/src/repo/s6rc_repo_setuptodate.c
@@ -6,6 +6,7 @@
 #include <string.h>
 #include <stdint.h>
 #include <errno.h>
+#include <unistd.h>
 
 #include <skalibs/stat.h>
 #include <skalibs/strerr.h>
@@ -34,12 +35,43 @@ int s6rc_repo_setuptodate (char const *repo, char const *set)
     strerr_warnfusys("stat ", srcfn) ;
     return -1 ;
   }
+
+ /* Do we have a compiled db for this set? */
   if (stat(dstfn, &stcompiled) == -1)
   {
     if (errno == ENOENT) return 0 ;
     strerr_warnfusys("stat ", dstfn) ;
     return -1 ;
   }
+
+ /* Do we have a snapshot of the source set for the compiled db? */
+  {
+    struct stat stsnap ;
+    char snap[repolen + 54 + setlen] ;
+    ssize_t r ;
+    memcpy(snap, srcfn, repolen + 9) ;
+    memcpy(snap + repolen + 9, ".snapshot", 9) ;
+    r = readlink(dstfn, snap + repolen + 18, setlen + 35) ;
+    if (r == -1)
+    {
+      strerr_warnfusys("readlink ", dstfn) ;
+      return -1 ;
+    }
+    if (r != setlen + 34)
+    {
+      strerr_warnf("invalid symlink: ", dstfn) ;
+      return -1 ;
+    }
+    snap[repolen + setlen + 53] = 0 ;
+    if (stat(snap, &stsnap) == -1)
+    {
+      if (errno == ENOENT) return 0 ;
+      strerr_warnfusys("stat ", snap) ;
+      return -1 ;
+    }
+  }
+
+ /* Has the compiled db been built with the latest major s6-rc version? */
   {
     uint32_t version = s6rc_repo_read_major(dstfn) ;
     if (!version)
@@ -49,6 +81,8 @@ int s6rc_repo_setuptodate (char const *repo, char const *set)
     }
     if (version < s6rc_get_major(S6RC_VERSION)) return 0 ;
   }
+
+ /* Is the compiled db more recent than the source set? */
   return
     stsource.st_mtim.tv_sec < stcompiled.st_mtim.tv_sec ? 1 :
     stsource.st_mtim.tv_sec > stcompiled.st_mtim.tv_sec ? 0 :