hints: new pvs_online type

A new form of hints to use in autoactivation commands
during startup to reduce device scanning.  Using these
hints, vgchange will read only the devices for the VG
it is activating.

Standard hints allow a command with a named VG arg to scan
only the PVs in the named VG, rather than scanning all
available PVs.  Standard hints are useful with a stable set
of system devices.  When new devices are arriving, as occurs
during system startup, the hints are repeatedly invalidated,
which makes standard hints unhelpful while devices are
regularly appearing.  This is the situation in which
vgchange -aay is used, so standard hints are not generally
helpful for autoactivation.

In the context of system startup, pvscan --cache is keeping
track of available PVs using the pvs_online files, similar
to what the hints file does for a running system.  Given this,
a new hint mode, hints = "pvs_online", is added which derives
an equivalent to standard hints, based on pvs_online files
that are being created by udev-run pvscans.  This hint mode
is useful while devices are appearing, e.g. during system
startup, and vgchange -aay can benefit from it.

pvscan --cache -aay autoactivation already has a similar
optimization (the "quick" activation case) that is based
on the pvs_online file, but it is not implemented as a
form of hints.

This new form of hints is mainly useful in the context of
event based autoactivation, during which standard hints are
not useful.  Once the system is in a steady state after startup
(devices are not regularly appearing), the standard hints are
most useful.  The pvs_online hint method could be used on a
running system, but would be no better than standard hints,
and may be inferior because pvs_online files are not rigidly
updated after system startup.

5 files changed, 129 insertions, 5 deletions

diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index 701b7a739..79da7d87d 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -183,6 +183,7 @@ struct cmd_context {
 	unsigned enable_hints:1;		/* hints are enabled for cmds in general */
 	unsigned use_hints:1;			/* if hints are enabled this cmd can use them */
 	unsigned pvscan_recreate_hints:1;	/* enable special case hint handling for pvscan --cache */
+	unsigned hints_pvs_online:1;		/* hints="pvs_online" */
 	unsigned scan_lvs:1;
 	unsigned wipe_outdated_pvs:1;
 	unsigned enable_devices_list:1;		/* command is using --devices option */
diff --git a/lib/config/defaults.h b/lib/config/defaults.h
index 1b1568a7b..3308b1ea6 100644
--- a/lib/config/defaults.h
+++ b/lib/config/defaults.h
@@ -328,4 +328,8 @@
 
 #define DEFAULT_WWIDS_FILE "/etc/multipath/wwids"
 
+#define PVS_ONLINE_DIR DEFAULT_RUN_DIR "/pvs_online"
+#define VGS_ONLINE_DIR DEFAULT_RUN_DIR "/vgs_online"
+#define PVS_LOOKUP_DIR DEFAULT_RUN_DIR "/pvs_lookup"
+
 #endif				/* _LVM_DEFAULTS_H */
diff --git a/lib/label/hints.c b/lib/label/hints.c
index 3dba9f8ec..4caadf774 100644
--- a/lib/label/hints.c
+++ b/lib/label/hints.c
@@ -150,11 +150,14 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <dirent.h>
 #include <time.h>
 #include <sys/types.h>
 #include <sys/file.h>
 #include <sys/sysmacros.h>
 
+int online_pvid_file_read(char *path, int *major, int *minor, char *vgname);
+
 static const char *_hints_file = DEFAULT_RUN_DIR "/hints";
 static const char *_nohints_file = DEFAULT_RUN_DIR "/nohints";
 static const char *_newhints_file = DEFAULT_RUN_DIR "/newhints";
@@ -1279,6 +1282,109 @@ check:
 	free(name);
 }
 
+static int _get_hints_from_pvs_online(struct cmd_context *cmd, struct dm_list *hints_out,
+				      struct dm_list *devs_in, struct dm_list *devs_out)
+{
+	char path[PATH_MAX];
+	char file_vgname[NAME_LEN];
+	struct dm_list hints_list;
+	struct hint file_hint;
+	struct hint *alloc_hint;
+	struct hint *hint, *hint2;
+	struct device_list *devl, *devl2;
+	int file_major, file_minor;
+	int found = 0;
+	DIR *dir;
+	struct dirent *de;
+	char *vgname = NULL;
+	char *pvid;
+
+	dm_list_init(&hints_list);
+
+	if (!(dir = opendir(PVS_ONLINE_DIR)))
+		return 0;
+
+	while ((de = readdir(dir))) {
+		if (de->d_name[0] == '.')
+			continue;
+
+		pvid = de->d_name;
+
+		if (strlen(pvid) != ID_LEN) /* 32 */
+			continue;
+
+		memset(path, 0, sizeof(path));
+		snprintf(path, sizeof(path), "%s/%s", PVS_ONLINE_DIR, pvid);
+
+		memset(&file_hint, 0, sizeof(file_hint));
+		memset(file_vgname, 0, sizeof(file_vgname));
+		file_major = 0;
+		file_minor = 0;
+
+		if (!online_pvid_file_read(path, &file_major, &file_minor, file_vgname))
+			continue;
+
+		if (!dm_strncpy(file_hint.pvid, pvid, sizeof(file_hint.pvid)))
+			continue;
+
+		file_hint.devt = makedev(file_major, file_minor);
+
+		if (file_vgname[0] && validate_name(file_vgname)) {
+			if (!dm_strncpy(file_hint.vgname, file_vgname, sizeof(file_hint.vgname)))
+				continue;
+		}
+
+		if (!(alloc_hint = malloc(sizeof(struct hint))))
+			continue;
+
+		memcpy(alloc_hint, &file_hint, sizeof(struct hint));
+
+		log_debug("add hint %s %d:%d %s from pvs_online", file_hint.pvid, file_major, file_minor, file_vgname);
+		dm_list_add(&hints_list, &alloc_hint->list);
+		found++;
+	}
+
+	if (closedir(dir))
+		stack;
+
+	log_debug("accept hints found %d from pvs_online", found);
+
+	_get_single_vgname_cmd_arg(cmd, &hints_list, &vgname);
+
+	/*
+	 * apply_hints equivalent, move devs from devs_in to devs_out if
+	 * their devno matches the devno of a hint (and if the hint matches
+	 * the vgname when a vgname is present.)
+	 */
+	dm_list_iterate_items_safe(devl, devl2, devs_in) {
+		dm_list_iterate_items_safe(hint, hint2, &hints_list) {
+			if ((MAJOR(devl->dev->dev) == MAJOR(hint->devt)) &&
+			    (MINOR(devl->dev->dev) == MINOR(hint->devt))) {
+
+				if (vgname && hint->vgname[0] && strcmp(vgname, hint->vgname))
+					goto next_dev;
+
+				snprintf(hint->name, sizeof(hint->name), "%s", dev_name(devl->dev));
+				hint->chosen = 1;
+
+				dm_list_del(&devl->list);
+				dm_list_add(devs_out, &devl->list);
+			}
+		}
+ next_dev:
+		;
+	}
+
+	log_debug("applied hints using %d other %d vgname %s from pvs_online",
+		  dm_list_size(devs_out), dm_list_size(devs_in), vgname ?: "");
+
+	dm_list_splice(hints_out, &hints_list);
+
+	free(vgname);
+
+	return 1;
+}
+
 /*
  * Returns 0: no hints are used.
  *  . newhints is set if this command should create new hints after scan
@@ -1320,6 +1426,15 @@ int get_hints(struct cmd_context *cmd, struct dm_list *hints_out, int *newhints,
 	if (!cmd->use_hints)
 		return 0;
 
+	/* hints = "pvs_online" */
+	if (cmd->hints_pvs_online) {
+		if (!_get_hints_from_pvs_online(cmd, &hints_list, devs_in, devs_out)) {
+			log_debug("get_hints: pvs_online failed");
+			return 0;
+		}
+		return 1;
+	}
+
 	/*
 	 * Check if another command created the nohints file to prevent us from
 	 * using hints.
diff --git a/tools/lvmcmdline.c b/tools/lvmcmdline.c
index 1e12bedca..9cbeab91d 100644
--- a/tools/lvmcmdline.c
+++ b/tools/lvmcmdline.c
@@ -2540,6 +2540,8 @@ static int _get_current_settings(struct cmd_context *cmd)
 		if (!strcmp(hint_mode, "none")) {
 			cmd->enable_hints = 0;
 			cmd->use_hints = 0;
+		} else if (!strcmp(hint_mode, "pvs_online")) {
+			cmd->hints_pvs_online = 1;
 		}
 	}
 
diff --git a/tools/pvscan.c b/tools/pvscan.c
index 7d84e45d4..01f57af0c 100644
--- a/tools/pvscan.c
+++ b/tools/pvscan.c
@@ -21,6 +21,8 @@
 
 #include <dirent.h>
 
+int online_pvid_file_read(char *path, int *major, int *minor, char *vgname);
+
 struct pvscan_params {
 	int new_pvs_found;
 	int pvs_found;
@@ -225,7 +227,7 @@ static char *_vgname_in_pvid_file_buf(char *buf)
 
 #define MAX_PVID_FILE_SIZE 512
 
-static int _online_pvid_file_read(char *path, int *major, int *minor, char *vgname)
+int online_pvid_file_read(char *path, int *major, int *minor, char *vgname)
 {
 	char buf[MAX_PVID_FILE_SIZE] = { 0 };
 	char *name;
@@ -328,7 +330,7 @@ static void _online_pvid_file_remove_devno(int major, int minor)
 		file_minor = 0;
 		memset(file_vgname, 0, sizeof(file_vgname));
 
-		_online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
+		online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
 
 		if ((file_major == major) && (file_minor == minor)) {
 			log_debug("Unlink pv online %s", path);
@@ -447,7 +449,7 @@ check_duplicate:
 
 	memset(file_vgname, 0, sizeof(file_vgname));
 
-	_online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
+	online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
 
 	if ((file_major == major) && (file_minor == minor)) {
 		log_debug("Existing online file for %d:%d", major, minor);
@@ -847,7 +849,7 @@ static int _get_devs_from_saved_vg(struct cmd_context *cmd, const char *vgname,
 		file_minor = 0;
 		memset(file_vgname, 0, sizeof(file_vgname));
 
-		_online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
+		online_pvid_file_read(path, &file_major, &file_minor, file_vgname);
 
 		if (file_vgname[0] && strcmp(vgname, file_vgname)) {
 			log_error_pvscan(cmd, "Wrong VG found for %d:%d PVID %s: %s vs %s",
@@ -1254,7 +1256,7 @@ static void _set_pv_devices_online(struct cmd_context *cmd, struct volume_group
 		minor = 0;
 		file_vgname[0] = '\0';
 
-		_online_pvid_file_read(path, &major, &minor, file_vgname);
+		online_pvid_file_read(path, &major, &minor, file_vgname);
 
 		if (file_vgname[0] && strcmp(vg->name, file_vgname)) {
 			log_warn("WARNING: VG %s PV %s wrong vgname in online file %s",