Relocate calls to CheckDiskSpace

Make sure we're checking disk space for block index writes and allow for pruning to happen before chainstate writes.

src/main.cpp

@@ -1919,12 +1919,8 @@ bool static FlushStateToDisk(CValidationState &state, FlushStateMode mode) {
     bool fDoFullFlush = (mode == FLUSH_STATE_ALWAYS) || fCacheLarge || fCacheCritical || fPeriodicFlush || fFlushForPrune;
     // Write blocks and block index to disk.
     if (fDoFullFlush || fPeriodicWrite) {
-        // Typical CCoins structures on disk are around 128 bytes in size.
-        // Pushing a new one to the database can cause it to be written
-        // twice (once in the log, and once in the tables). This is already
-        // an overestimation, as most will delete an existing entry or
-        // overwrite one. Still, use a conservative safety factor of 2.
-        if (fDoFullFlush && !CheckDiskSpace(128 * 2 * 2 * pcoinsTip->GetCacheSize()))
+        // Depend on nMinDiskSpace to ensure we can write block index
+        if (!CheckDiskSpace(0))
             return state.Error("out of disk space");
         // First make sure all block and undo data is flushed to disk.
         FlushBlockFile();
@@ -1955,6 +1951,13 @@ bool static FlushStateToDisk(CValidationState &state, FlushStateMode mode) {
     }
     // Flush best chain related state. This can only be done if the blocks / block index write was also done.
     if (fDoFullFlush) {
+        // Typical CCoins structures on disk are around 128 bytes in size.
+        // Pushing a new one to the database can cause it to be written
+        // twice (once in the log, and once in the tables). This is already
+        // an overestimation, as most will delete an existing entry or
+        // overwrite one. Still, use a conservative safety factor of 2.
+        if (!CheckDiskSpace(128 * 2 * 2 * pcoinsTip->GetCacheSize()))
+            return state.Error("out of disk space");
         // Flush the chainstate (which may refer to block index entries).
         if (!pcoinsTip->Flush())
             return state.Abort("Failed to write to coin database");