exportfs - test exportability of filesystems when exportfs is run.

When exporting a filesystem test to see if the kernel is likely
to accept the export and print suitable warning message if not.
Don't actually fail the 'exportfs' as by the time a MOUNT request
arrives, the filesystem might be exportable.

Signed-off-by: Neil Brown <neilb@suse.de>

diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
index 8c3f634de5984848de3ccc61037774ecbf89f791..99618c94ee0ed0040f29a32246b3af50d2824539 100644 (file)
--- a/utils/exportfs/exportfs.c
+++ b/utils/exportfs/exportfs.c
@@ -12,6 +12,7 @@
 #include <config.h>
 #endif
 
+#include <unistd.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
@@ -32,7 +33,7 @@ static void   exports_update(int verbose);
 static void    dump(int verbose);
 static void    error(nfs_export *exp, int err);
 static void    usage(void);
-
+static void    validate_export(nfs_export *exp);
 
 int
 main(int argc, char **argv)
@@ -219,6 +220,7 @@ export_all(int verbose)
                        exp->m_mayexport = 1;
                        exp->m_changed = 1;
                        exp->m_warned = 0;
+                       validate_export(exp);
                }
        }
 }
@@ -276,6 +278,7 @@ exportfs(char *arg, char *options, int verbose)
        exp->m_mayexport = 1;
        exp->m_changed = 1;
        exp->m_warned = 0;
+       validate_export(exp);
        if (hp) free (hp);
 }
 
@@ -340,6 +343,87 @@ unexportfs(char *arg, int verbose)
        if (hp) free (hp);
 }
 
+static int can_test(void)
+{
+       int fd;
+       int n;
+       char *setup = "nfsd 0.0.0.0 2147483647 -test-client-\n";
+       fd = open("/proc/net/rpc/auth.unix.ip/channel", O_WRONLY);
+       if ( fd < 0) return 0;
+       n = write(fd, setup, strlen(setup));
+       close(fd);
+       if (n < 0)
+               return 0;
+       fd = open("/proc/net/rpc/nfsd.export/channel", O_WRONLY);
+       if ( fd < 0) return 0;
+       close(fd);
+       return 1;
+}
+
+static int test_export(char *path, int with_fsid)
+{
+       char buf[1024];
+       int fd, n;
+
+       sprintf(buf, "-test-client- %s 3 %d -1 -1 0\n",
+               path,
+               with_fsid ? NFSEXP_FSID : 0);
+       fd = open("/proc/net/rpc/nfsd.export/channel", O_WRONLY);
+       if (fd < 0)
+               return 0;
+       n = write(fd, buf, strlen(buf));
+       close(fd);
+       if (n < 0)
+               return 0;
+       return 1;
+}
+
+static void
+validate_export(nfs_export *exp)
+{
+       /* Check that the given export point is potentially exportable.
+        * We just give warnings here, don't cause anything to fail.
+        * If a path doesn't exist, or is not a dir or file, give an warning
+        * otherwise trial-export to '-test-client-' and check for failure.
+        */
+       struct stat stb;
+       char *path = exp->m_export.e_path;
+
+       if (stat(path, &stb) < 0) {
+               fprintf(stderr, "exportfs: Warning: %s does not exist\n",
+                       path);
+               return;
+       }
+       if (!S_ISDIR(stb.st_mode) && !S_ISREG(stb.st_mode)) {
+               fprintf(stderr, "exportfs: Warning: %s is neither "
+                       "a directory nor a file.\n"
+                       "     remote access will fail\n", path);
+               return;
+       }
+       if (!can_test())
+               return;
+
+       if ((exp->m_export.e_flags & NFSEXP_FSID) || exp->m_export.e_uuid) {
+               if ( !test_export(path, 1)) {
+                       fprintf(stderr, "exportfs: Warning: %s does not "
+                               "support NFS export.\n",
+                               path);
+                       return;
+               }
+       } else if ( ! test_export(path, 0)) {
+               if (test_export(path, 1))
+                       fprintf(stderr, "exportfs: Warning: %s requires fsid= "
+                               "for NFS export\n", path);
+               else
+                       fprintf(stderr, "exportfs: Warning: %s does not "
+                               "support NFS export.\n",
+                               path);
+               return;
+
+       }
+}
+
+
 static char
 dumpopt(char c, char *fmt, ...)
 {