add hints interface to the pvs_online file information

The information in /run/lvm/pvs_online/<pvid> files can
be used to build a list of devices for a given VG.

The pvscan -aay command has long used this information to
activate a VG while scanning only devices in that VG, which
is an important optimization for autoactivation.

This patch implements the same thing through the existing
device hints interface, so that the optimization can be
applied elsewhere.  A future patch will take advantage of
this optimization in vgchange -aay, which is now used in
place of pvscan -aay for event activation.

2 files changed, 123 insertions, 1 deletions

diff --git a/lib/label/hints.c b/lib/label/hints.c
index e444a0c82..c84bd1f1c 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";
@@ -1278,6 +1281,109 @@ 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
@@ -1299,7 +1405,7 @@ int get_hints(struct cmd_context *cmd, struct dm_list *hints_out, int *newhints,
 	*newhints = NEWHINTS_NONE;
 
 	/* No commands are using hints. */
-	if (!cmd->enable_hints)
+	if (!cmd->enable_hints && !cmd->hints_pvs_online)
 		return 0;
 
 	/*
@@ -1320,6 +1426,19 @@ int get_hints(struct cmd_context *cmd, struct dm_list *hints_out, int *newhints,
 		return 0;
 
 	/*
+	 * enable_hints is 0 for the special hints=pvs_online
+	 * and by lvm.conf hints="none" does not disable hints=pvs_online.
+	 * hints=pvs_online can be disabled with --nohints.
+	 */
+	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/lib/label/label.c b/lib/label/label.c
index 9fac3e464..f9ab9a1f1 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -1130,6 +1130,9 @@ int label_scan(struct cmd_context *cmd)
 			}
 		}
 	}
+
+	log_debug_devs("Filtering devices to scan done (nodata)");
+
 	cmd->filter_nodata_only = 0;
 
 	dm_list_iterate_items(devl, &all_devs)