autofs-5.1.8 - use device id to locate autofs_point when setting log priotity

From: Ian Kent <raven@themaw.net>

Using a fifo pipe for every autofs mount to dynamically set the log
priority is expensive in terms of the number of file handles used.

It would be better to use a single file handle and locate the autofs
mount point by it's id to set the log priority.

Start by making the communication pipe send the device id as well as
the log priority to be set and use the newly added helper function
master_find_mapent_by_devid() to locate the autofs mount to change the
log priority.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 CHANGELOG          |    1 +
 daemon/automount.c |   63 ++++++++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 5af03a7d..86326a8d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -65,6 +65,7 @@
 - make signal handling consistent.
 - eliminate last remaining state_pipe usage.
 - add function master_find_mapent_by_devid().
+- use device id to locate autofs_point when setting log priotity.
 
 19/10/2021 autofs-5.1.8
 - add xdr_exports().
diff --git a/daemon/automount.c b/daemon/automount.c
index 840c178a..1164198e 100644
--- a/daemon/automount.c
+++ b/daemon/automount.c
@@ -69,6 +69,8 @@ unsigned int mp_mode = 0755;
 unsigned int nfs_mount_uses_string_options = 0;
 static struct nfs_mount_vers vers, check = {1, 1, 1};
 
+#define FIFO_BUF_SIZE		25
+
 /* autofs fifo name prefix */
 #define FIFO_NAME_PREFIX "autofs.fifo"
 const char *fifodir = AUTOFS_FIFO_DIR "/" FIFO_NAME_PREFIX;
@@ -961,35 +963,57 @@ static void cleanup_stale_logpri_fifo_pipes(void)
 	closedir(dfd);
 }
 
-static void handle_fifo_message(struct autofs_point *ap, int fd)
+static void handle_fifo_message(int fd)
 {
+	struct autofs_point *ap;
 	int ret;
 	char buffer[PIPE_BUF];
-	char *end;
+	char *end, *sep;
 	long pri;
 	char buf[MAX_ERR_BUF];
+	dev_t devid;
 
 	memset(buffer, 0, sizeof(buffer));
 	ret = read(fd, &buffer, sizeof(buffer));
 	if (ret < 0) {
 		char *estr = strerror_r(errno, buf, MAX_ERR_BUF);
-		warn(ap->logopt, "read on fifo returned error: %s", estr);
+		warn(LOGOPT_ANY, "read on fifo returned error: %s", estr);
+		return;
+	}
+
+	sep = strrchr(buffer, ' ');
+	if (!sep) {
+		error(LOGOPT_ANY, "Incorrect cmd message format %s.", buffer);
+		return;
+	}
+	sep++;
+
+	errno = 0;
+	devid = strtol(buffer, &end, 10);
+	if ((devid == LONG_MIN || devid == LONG_MAX) && errno == ERANGE) {
+		debug(LOGOPT_ANY, "strtol reported a range error.");
+		error(LOGOPT_ANY, "Invalid cmd message format %s.", buffer);
+		return;
+	}
+	if ((devid == 0 && errno == EINVAL) || end == buffer) {
+		debug(LOGOPT_ANY, "devid id is expected to be a integer.");
 		return;
 	}
 
-	if (ret != 2) {
-		debug(ap->logopt, "expected 2 bytes, received %d.", ret);
+	ap = master_find_mapent_by_devid(master_list, devid);
+	if (!ap) {
+		error(LOGOPT_ANY, "Can't locate autofs_point for device id %ld.", devid);
 		return;
 	}
 
 	errno = 0;
-	pri = strtol(buffer, &end, 10);
+	pri = strtol(sep, &end, 10);
 	if ((pri == LONG_MIN || pri == LONG_MAX) && errno == ERANGE) {
 		debug(ap->logopt, "strtol reported an %s.  Failed to set "
 		      "log priority.", pri == LONG_MIN ? "underflow" : "overflow");
 		return;
 	}
-	if ((pri == 0 && errno == EINVAL) || end == buffer) {
+	if ((pri == 0 && errno == EINVAL) || end == sep) {
 		debug(ap->logopt, "priority is expected to be an integer "
 		      "in the range 0-7 inclusive.");
 		return;
@@ -1026,9 +1050,24 @@ static void handle_fifo_message(struct autofs_point *ap, int fd)
 
 static int set_log_priority(const char *path, int priority)
 {
+	struct ioctl_ops *ops = get_ioctl_ops();
 	int fd;
 	char *fifo_name;
-	char buf[2];
+	char buf[FIFO_BUF_SIZE];
+	int ret;
+	dev_t devid;
+
+	if (!ops) {
+		fprintf(stderr, "Could not get ioctl ops\n");
+		return -1;
+	} else {
+		ret = ops->mount_device(LOGOPT_ANY, path, 0, &devid);
+		if (ret == -1 || ret == 0) {
+			fprintf(stderr,
+				"Could not find device id for mount %s\n", path);
+			return -1;
+		}
+	}
 
 	if (priority > LOG_DEBUG || priority < LOG_EMERG) {
 		fprintf(stderr, "Log priority %d is invalid.\n", priority);
@@ -1040,7 +1079,11 @@ static int set_log_priority(const char *path, int priority)
 	 * This is an ascii based protocol, so we want the string
 	 * representation of the integer log priority.
 	 */
-	snprintf(buf, sizeof(buf), "%d", priority);
+	ret = snprintf(buf, sizeof(buf), "%ld %d", devid, priority);
+	if (ret >= FIFO_BUF_SIZE) {
+		fprintf(stderr, "Invalid device id or log priotity\n");
+		return -1;
+	}
 
 	fifo_name = automount_path_to_fifo(LOGOPT_NONE, path);
 	if (!fifo_name) {
@@ -1139,7 +1182,7 @@ static int get_pkt(struct autofs_point *ap, union autofs_v5_packet_union *pkt)
 
 		if (fds[1].fd != -1 && fds[1].revents & POLLIN) {
 			debug(ap->logopt, "message pending on control fifo.");
-			handle_fifo_message(ap, fds[1].fd);
+			handle_fifo_message(fds[1].fd);
 		}
 	}
 }