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Fix mountd so that it will not lose SIGHUPs that indicate "reload exports".

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Without this patch, if a SIGHUP is handled while the process is executing
get_exportlist(), that SIGHUP is essentially ignored because the got_sighup
variable is reset to 0 after get_exportlist().
This results in the exports file(s) not being reloaded until another SIGHUP
signal is sent to mountd.
This patch fixes this by resetting got_sighup to zero before the
get_exportlist() call while SIGHUP is blocked.
It also defines a delay time of 250msec before doing another exports reload
if there are RPC request(s) to process. This prevents repeated exports reloads
from delaying handling of RPC requests significantly.

PR:		246597
Reported by:	patrykkotlowski@gmail.com
Tested by:	patrykkotlowski@gmail.com
Reviewed by:	markj
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D25127
This commit is contained in:
Rick Macklem 2020-06-06 00:40:02 +00:00
parent 24ed6f550a
commit 7674d489fc
1 changed files with 46 additions and 6 deletions
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52
usr.sbin/mountd/mountd.c
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@ -184,6 +184,12 @@ struct fhreturn {
#define GETPORT_MAXTRY 20 /* Max tries to get a port # */
/*
* How long to delay a reload of exports when there are RPC request(s)
* to process, in usec. Must be less than 1second.
*/
#define RELOADDELAY 250000
/* Global defs */
static char *add_expdir(struct dirlist **, char *, int);
static void add_dlist(struct dirlist **, struct dirlist *,
@ -410,6 +416,10 @@ main(int argc, char **argv)
int maxrec = RPC_MAXDATASIZE;
int attempt_cnt, port_len, port_pos, ret;
char **port_list;
uint64_t curtime, nexttime;
struct timeval tv;
struct timespec tp;
sigset_t sighup_mask;
/* Check that another mountd isn't already running. */
pfh = pidfile_open(_PATH_MOUNTDPID, 0600, &otherpid);
@ -665,19 +675,49 @@ main(int argc, char **argv)
}
/* Expand svc_run() here so that we can call get_exportlist(). */
curtime = nexttime = 0;
sigemptyset(&sighup_mask);
sigaddset(&sighup_mask, SIGHUP);
for (;;) {
if (got_sighup) {
get_exportlist(1);
clock_gettime(CLOCK_MONOTONIC, &tp);
curtime = tp.tv_sec;
curtime = curtime * 1000000 + tp.tv_nsec / 1000;
sigprocmask(SIG_BLOCK, &sighup_mask, NULL);
if (got_sighup && curtime >= nexttime) {
got_sighup = 0;
}
sigprocmask(SIG_UNBLOCK, &sighup_mask, NULL);
get_exportlist(1);
clock_gettime(CLOCK_MONOTONIC, &tp);
nexttime = tp.tv_sec;
nexttime = nexttime * 1000000 + tp.tv_nsec / 1000 +
RELOADDELAY;
} else
sigprocmask(SIG_UNBLOCK, &sighup_mask, NULL);
/*
* If a reload is pending, poll for received request(s),
* otherwise set a RELOADDELAY timeout, since a SIGHUP
* could be processed between the got_sighup test and
* the select() system call.
*/
tv.tv_sec = 0;
if (got_sighup)
tv.tv_usec = 0;
else
tv.tv_usec = RELOADDELAY;
readfds = svc_fdset;
switch (select(svc_maxfd + 1, &readfds, NULL, NULL, NULL)) {
switch (select(svc_maxfd + 1, &readfds, NULL, NULL, &tv)) {
case -1:
if (errno == EINTR)
continue;
if (errno == EINTR) {
/* Allow a reload now. */
nexttime = 0;
continue;
}
syslog(LOG_ERR, "mountd died: select: %m");
exit(1);
case 0:
/* Allow a reload now. */
nexttime = 0;
continue;
default:
svc_getreqset(&readfds);