Enumerate available tablespaces after starting the backup

This closes a race condition where if a tablespace was created
after the enumeration happened but before the do_pg_start_backup()
was called, the backup would be incomplete. Now that it's done
while we are in backup mode, WAL replay will recreate it during
restore.

Noted by Heikki.

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 1ed5e2a..b4d5bbe 100644 (file)
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -40,7 +40,7 @@ static void send_int8_string(StringInfoData *buf, int64 intval);
 static void SendBackupHeader(List *tablespaces);
 static void SendBackupDirectory(char *location, char *spcoid);
 static void base_backup_cleanup(int code, Datum arg);
-static void perform_base_backup(const char *backup_label, List *tablespaces);
+static void perform_base_backup(const char *backup_label, bool progress, DIR *tblspcdir);
 
 typedef struct
 {
@@ -67,13 +67,50 @@ base_backup_cleanup(int code, Datum arg)
  * clobbered by longjmp" from stupider versions of gcc.
  */
 static void
-perform_base_backup(const char *backup_label, List *tablespaces)
+perform_base_backup(const char *backup_label, bool progress, DIR *tblspcdir)
 {
        do_pg_start_backup(backup_label, true);
 
        PG_ENSURE_ERROR_CLEANUP(base_backup_cleanup, (Datum) 0);
        {
+               List       *tablespaces = NIL;
                ListCell   *lc;
+               struct dirent *de;
+               tablespaceinfo *ti;
+
+
+               /* Add a node for the base directory */
+               ti = palloc0(sizeof(tablespaceinfo));
+               ti->size = progress ? sendDir(".", 1, true) : -1;
+               tablespaces = lappend(tablespaces, ti);
+
+               /* Collect information about all tablespaces */
+               while ((de = ReadDir(tblspcdir, "pg_tblspc")) != NULL)
+               {
+                       char            fullpath[MAXPGPATH];
+                       char            linkpath[MAXPGPATH];
+
+                       /* Skip special stuff */
+                       if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
+                               continue;
+
+                       snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name);
+
+                       MemSet(linkpath, 0, sizeof(linkpath));
+                       if (readlink(fullpath, linkpath, sizeof(linkpath) - 1) == -1)
+                       {
+                               ereport(WARNING,
+                                               (errmsg("unable to read symbolic link %s: %m", fullpath)));
+                               continue;
+                       }
+
+                       ti = palloc(sizeof(tablespaceinfo));
+                       ti->oid = pstrdup(de->d_name);
+                       ti->path = pstrdup(linkpath);
+                       ti->size = progress ? sendDir(linkpath, strlen(linkpath), true) : -1;
+                       tablespaces = lappend(tablespaces, ti);
+               }
+
 
                /* Send tablespace header */
                SendBackupHeader(tablespaces);
@@ -101,9 +138,6 @@ void
 SendBaseBackup(const char *backup_label, bool progress)
 {
        DIR                *dir;
-       struct dirent *de;
-       List       *tablespaces = NIL;
-       tablespaceinfo *ti;
        MemoryContext backup_context;
        MemoryContext old_context;
 
@@ -134,41 +168,10 @@ SendBaseBackup(const char *backup_label, bool progress)
                ereport(ERROR,
                                (errmsg("unable to open directory pg_tblspc: %m")));
 
-       /* Add a node for the base directory */
-       ti = palloc0(sizeof(tablespaceinfo));
-       ti->size = progress ? sendDir(".", 1, true) : -1;
-       tablespaces = lappend(tablespaces, ti);
-
-       /* Collect information about all tablespaces */
-       while ((de = ReadDir(dir, "pg_tblspc")) != NULL)
-       {
-               char            fullpath[MAXPGPATH];
-               char            linkpath[MAXPGPATH];
-
-               /* Skip special stuff */
-               if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
-                       continue;
-
-               snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name);
-
-               MemSet(linkpath, 0, sizeof(linkpath));
-               if (readlink(fullpath, linkpath, sizeof(linkpath) - 1) == -1)
-               {
-                       ereport(WARNING,
-                                 (errmsg("unable to read symbolic link %s: %m", fullpath)));
-                       continue;
-               }
+       perform_base_backup(backup_label, progress, dir);
 
-               ti = palloc(sizeof(tablespaceinfo));
-               ti->oid = pstrdup(de->d_name);
-               ti->path = pstrdup(linkpath);
-               ti->size = progress ? sendDir(linkpath, strlen(linkpath), true) : -1;
-               tablespaces = lappend(tablespaces, ti);
-       }
        FreeDir(dir);
 
-       perform_base_backup(backup_label, tablespaces);
-
        MemoryContextSwitchTo(old_context);
        MemoryContextDelete(backup_context);
 }