Do not hardcode umount(8) path, emulate lazy umount

1) Use a system-dependent macro for umount(8) location instead of
relying on $PATH  to find it, for security and portability sake.

2) Introduce gf_umount_lazy() to replace umount -l (-l for lazy) invocations,
which is only supported on Linux; On Linux behavior in unchanged. On other
systems, we fork an external process (umountd) that will take care of
periodically attempt to unmount, and optionally rmdir.

BUG: 1129939
Change-Id: Ia91167c0652f8ddab85136324b08f87c5ac1e51d
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/8649
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Csaba Henk <csaba@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

2 files changed, 257 insertions, 0 deletions

diff --git a/contrib/umountd/Makefile.am b/contrib/umountd/Makefile.am
new file mode 100644
index 00000000000..c03b0cbcae6
--- /dev/null
+++ b/contrib/umountd/Makefile.am
@@ -0,0 +1,10 @@
+sbin_PROGRAMS = umountd
+umountd_SOURCES = umountd.c
+umountd_CFLAGS = $(GF_CFLAGS) -DDATADIR=\"$(localstatedir)\"
+umountd_LDADD = $(top_builddir)/libglusterfs/src/libglusterfs.la ${GF_LDADD}
+umountd_LDFLAGS = $(GF_LDFLAGS)
+
+AM_CPPFLAGS = $(GF_CPPFLAGS) -I$(top_srcdir)/libglusterfs/src 
+AM_CFLAGS = -Wall $(GF_CFLAGS)
+
+CLEANFILES =
diff --git a/contrib/umountd/umountd.c b/contrib/umountd/umountd.c
new file mode 100644
index 00000000000..42f867d1983
--- /dev/null
+++ b/contrib/umountd/umountd.c
@@ -0,0 +1,247 @@
+/*
+  Copyright (c) 2008-2012 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <dirent.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+
+#include "glusterfs.h"
+#include "globals.h"
+#include "logging.h"
+#include "syscall.h"
+#include "mem-types.h"
+
+static void
+usage (void)
+{
+        fprintf (stderr, "Usage: umountd [-d dev] [-t timeout] [-r] path\n");
+        exit (EXIT_FAILURE);
+}
+
+
+static int
+sanity_check (char *path, dev_t *devp)
+{
+        struct stat st;
+        struct stat parent_st;
+        int ret;
+        char pathtmp[PATH_MAX];
+        char *parent;
+
+        if (path == NULL)
+                usage ();
+
+        if (stat (path, &st) != 0) {
+                gf_log ("umountd", GF_LOG_ERROR,
+                        "Cannot access %s\n", path, strerror (errno));
+                goto out;
+        }
+
+        /* If dev was not specified, get it from path */
+        if (*devp == -1)
+                *devp = st.st_dev;
+
+        strncpy (pathtmp, path, PATH_MAX);
+        parent = dirname (pathtmp);
+
+        if (stat (parent, &parent_st) != 0) {
+                gf_log ("umountd", GF_LOG_ERROR,
+                        "Cannot access %s\n", parent, strerror (errno));
+                goto out;
+        }
+
+        if (st.st_dev == parent_st.st_dev) {
+                gf_log ("umountd", GF_LOG_ERROR,
+                        "No filesystem mounted on %s\n", path);
+                goto out;
+        }
+
+        ret = 0;
+
+out:
+        return ret;
+}
+
+static void
+log_rotate (int signum)
+{
+        gf_log_logrotate (1);
+
+        if (signal (SIGHUP, *log_rotate) == SIG_ERR) {
+                gf_log ("umountd", GF_LOG_ERROR, "signal () failed");
+                exit (EXIT_FAILURE);
+        }
+
+        return;
+}
+
+static int
+logging_init (void)
+{
+        glusterfs_ctx_t *ctx;
+        char log_file[PATH_MAX];
+        int ret = -1;
+
+        ctx = glusterfs_ctx_new ();
+        if (!ctx) {
+                fprintf (stderr, "glusterfs_ctx_new failed\n");
+                goto out;
+        }
+
+        ret = glusterfs_globals_init (ctx);
+        if (ret) {
+                fprintf (stderr, "glusterfs_globals_init failed\n");
+                goto out;
+        }
+
+        THIS->ctx = ctx;
+        xlator_mem_acct_init (THIS, gf_common_mt_end);
+
+        snprintf (log_file, PATH_MAX,
+                  "%s/umountd.log", DEFAULT_LOG_FILE_DIRECTORY);
+
+        ret = gf_log_init (ctx, log_file, "umountd");
+        if (ret) {
+                fprintf (stderr, "gf_log_init failed\n");
+                goto out;
+        }
+
+        if (signal (SIGHUP, *log_rotate) == SIG_ERR) {
+                gf_log ("umountd", GF_LOG_ERROR, "signal () failed");
+                goto out;
+        }
+
+        ret = 0;
+out:
+        return ret;
+}
+
+static int
+umountd_async (char *path, dev_t dev, int frmdir, int timeout)
+{
+        int                   ret        = -1;
+        struct stat           stbuf      = {0, };
+        int                       unmount_ret = 0;
+
+        do {
+                unmount_ret = unmount (path, 0);
+                if (unmount_ret == 0)
+                        gf_log ("umountd", GF_LOG_INFO, "Unmounted %s", path);
+
+                if (unmount_ret != 0 && errno != EBUSY) {
+                               gf_log ("umountd", GF_LOG_WARNING,
+                                      "umount %s failed: %s",
+                                path, strerror (errno));
+                }
+
+                ret = sys_lstat (path, &stbuf);
+                if (ret != 0) {
+                        gf_log ("umountd", GF_LOG_WARNING,
+                                      "Cannot stat device from %s",
+                                path, strerror (errno));
+                        break;
+                }
+
+                if (stbuf.st_dev != dev) {
+                        if (unmount_ret != 0)
+                                gf_log ("umountd", GF_LOG_INFO,
+                                        "device mismatch "
+                                        "(expect %lld, found %lld), "
+                                        "someone else unmounted %s",
+                                        dev, stbuf.st_dev, path);
+                        ret = 0;
+                        break;
+                }
+
+                sleep (timeout);
+        } while (1/*CONSTCOND*/);
+
+        if (ret) {
+                gf_log ("umountd", GF_LOG_ERROR,
+                        "Asynchronous unmount of %s failed: %s",
+                        path, strerror (errno));
+        } else {
+                if (frmdir) {
+                        ret = rmdir (path);
+                        if (ret)
+                                gf_log ("umountd", GF_LOG_WARNING,
+                                         "rmdir %s failed: %s",
+                                         path, strerror (errno));
+                        else
+                                gf_log ("umountd", GF_LOG_INFO,
+                                         "Removed %s", path);
+                }
+        }
+
+        return ret;
+}
+
+int
+main (int argc, char **argv)
+{
+        char *path = NULL;
+        dev_t dev = -1;
+        int frmdir = 0;
+        int timeout = 30;
+        int f;
+
+        while ((f = getopt (argc, argv, "d:rt:")) != -1) {
+                switch (f) {
+                case 'p':
+                        path = optarg;
+                        break;
+                case 'd':
+                        dev = strtoll (optarg, NULL, 10);
+                        break;
+                case 't':
+                        timeout = atoi (optarg);
+                        break;
+                case 'r':
+                        frmdir = 1;
+                        break;
+                default:
+                        usage ();
+                        break;
+                }
+        }
+
+        argc -= optind;
+        argv += optind;
+
+        if (argc != 1)
+                usage ();
+
+        path = argv[0];
+
+        if (logging_init () != 0)
+                exit (EXIT_FAILURE);
+
+        if (sanity_check (path, &dev) != 0)
+                exit (EXIT_FAILURE);
+
+        if (daemon (0, 0) != 0)
+                exit (EXIT_FAILURE);
+
+        if (umountd_async (path, dev, frmdir, timeout) != 0)
+                exit (EXIT_FAILURE);
+
+        return EXIT_SUCCESS;
+}