Don't actively violate the system limit of maximum open files (RLIMIT_NOFILE).

This avoids irritating kernel logs (if system overstep violations are enabled)
and also the grsecurity alert when starting PostgreSQL.

original patch by Jacek Drobiecki

References:
http://archives.postgresql.org/pgsql-bugs/2004-05/msg00103.php
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=248967

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index b91946a035052926415453c4eb22e99e6826fd40..7749d5a405233eb5201d5850ad882f7c4fee183a 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.147 2009/01/12 05:10:44 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.148 2009/03/04 09:12:49 petere Exp $
  *
  * NOTES:
  *
@@ -45,6 +45,9 @@
 #include 
 #include 
 #include 
+#ifdef HAVE_SYS_RESOURCE_H
+#include       /* for getrlimit */
+#endif
 
 #include "miscadmin.h"
 #include "access/xact.h"
@@ -361,15 +364,35 @@ count_usable_fds(int max_to_probe, int *usable_fds, int *already_open)
    int         used = 0;
    int         highestfd = 0;
    int         j;
+#ifdef HAVE_GETRLIMIT
+   struct rlimit rlim;
+   int         getrlimit_status;
+#endif
 
    size = 1024;
    fd = (int *) palloc(size * sizeof(int));
 
+#ifdef HAVE_GETRLIMIT
+# ifdef RLIMIT_NOFILE            /* most platforms use RLIMIT_NOFILE */
+   getrlimit_status = getrlimit(RLIMIT_NOFILE, &rlim);
+# else                           /* but BSD doesn't ... */
+   getrlimit_status = getrlimit(RLIMIT_OFILE, &rlim);
+# endif /* RLIMIT_NOFILE */
+   if (getrlimit_status != 0)
+       ereport(WARNING, (errmsg("getrlimit failed: %m")));
+#endif /* HAVE_GETRLIMIT */
+
    /* dup until failure or probe limit reached */
    for (;;)
    {
        int         thisfd;
 
+#ifdef HAVE_GETRLIMIT
+       /* don't go beyond RLIMIT_NOFILE; causes irritating kernel logs on some platforms */
+       if (getrlimit_status == 0 && highestfd >= rlim.rlim_cur - 1)
+           break;
+#endif
+
        thisfd = dup(0);
        if (thisfd < 0)
        {