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Add a new '-S' option to mountd, which tells it to suspend

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execution of the nfsd threads while it is reloading the exports.
This avoids clients from getting intermittent access errors
when the exports are being reloaded non-atomically.
It is not an ideal solution, since requests will back up while
the nfsd threads are suspended. Also, when this option is used,
if mountd crashes while reloading exports, mountd will have to
be restarted to get the nfsd threads to resume execution.
This has been tested by Vincent Hoffman (vince at unsane.co.uk)
and John Hickey (jh at deterlab.net).
The nfse patch offers a more comprehensive solution for this issue.

PR:		kern/9619, kern/131342
Reviewed by:	kib
MFC after:	2 weeks
This commit is contained in:
Rick Macklem 2012-10-15 00:17:16 +00:00
parent cf0c92d600
commit c548eb5cad
1 changed files with 11 additions and 2 deletions
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13
usr.sbin/mountd/mountd.c
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@ -246,6 +246,7 @@ static int mallocd_svcport = 0;
static int *sock_fd;
static int sock_fdcnt;
static int sock_fdpos;
static int suspend_nfsd = 0;
int opt_flags;
static int have_v6 = 1;
@ -311,7 +312,7 @@ main(int argc, char **argv)
else
close(s);
while ((c = getopt(argc, argv, "2deh:lnop:r")) != -1)
while ((c = getopt(argc, argv, "2deh:lnop:rS")) != -1)
switch (c) {
case '2':
force_v2 = 1;
@ -363,6 +364,9 @@ main(int argc, char **argv)
out_of_mem();
}
break;
case 'S':
suspend_nfsd = 1;
break;
default:
usage();
};
@ -921,7 +925,7 @@ usage(void)
{
fprintf(stderr,
"usage: mountd [-2] [-d] [-e] [-l] [-n] [-p <port>] [-r] "
"[-h <bindip>] [export_file ...]\n");
"[-S] [-h <bindip>] [export_file ...]\n");
exit(1);
}
@ -1659,6 +1663,8 @@ get_exportlist(void)
int done;
struct nfsex_args eargs;
if (suspend_nfsd != 0)
(void)nfssvc(NFSSVC_SUSPENDNFSD, NULL);
v4root_dirpath[0] = '\0';
bzero(&export, sizeof(export));
export.ex_flags = MNT_DELEXPORT;
@ -1787,6 +1793,9 @@ get_exportlist(void)
*/
if (run_v4server > 0 && has_publicfh == 0)
(void) nfssvc(NFSSVC_NOPUBLICFH, NULL);
/* Resume the nfsd. If they weren't suspended, this is harmless. */
(void)nfssvc(NFSSVC_RESUMENFSD, NULL);
}
/*