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 <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
+#ifdef HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>              /* 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)
                {