vg_read: use the same async read code as label scan

Both for rescanning labels at the start of vg_read,
and then passing and using that reread data through
the vg_read() path to avoid rereading the same data
from disk.

13 files changed, 302 insertions, 50 deletions

diff --git a/lib/cache/lvmcache.c b/lib/cache/lvmcache.c
index 0602d8e8f..e9a68f18f 100644
--- a/lib/cache/lvmcache.c
+++ b/lib/cache/lvmcache.c
@@ -1136,7 +1136,25 @@ next:
 	goto next;
 }
 
-int lvmcache_label_refresh_for_vg(struct cmd_context *cmd, const char *vgname, const char *vgid)
+/*
+ * The initial label_scan at the start of the command is done without
+ * holding VG locks.  Then for each VG identified during the label_scan,
+ * vg_read(vgname) is called while holding the VG lock.  The labels
+ * and metadata on this VG's devices could have changed between the
+ * initial unlocked label_scan and the current vg_read().  So, we reread
+ * the labels/metadata for each device in the VG now that we hold the
+ * lock, and use this for processing the VG.
+ *
+ * FIXME: In some cases, the data read by label_scan may be fine, and not
+ * need to be reread here. e.g. a reporting command, possibly with a
+ * special option, could skip this second reread.  Or, we could look
+ * at the VG seqno in each copy of the metadata read in the first label
+ * scan, and if they all match, consider it good enough to use for
+ * reporting without rereading it.  (A command modifying the VG would
+ * always want to reread while the lock is held before modifying.)
+ */
+
+int lvmcache_label_rescan_vg(struct cmd_context *cmd, const char *vgname, const char *vgid)
 {
 	struct dm_list devs;
 	struct device_list *devl;
@@ -1160,10 +1178,8 @@ int lvmcache_label_refresh_for_vg(struct cmd_context *cmd, const char *vgname, c
 		dm_list_add(&devs, &devl->list);
 	}
 
-	dm_list_iterate_items(devl, &devs) {
-		log_debug_cache("Reading label on %s for VG %s", dev_name(devl->dev), vgname);
-		label_read(devl->dev, NULL, 0);
-	}
+	if (!cmd->use_aio || !label_rescan_async(cmd, &devs))
+		label_rescan_sync(cmd, &devs);
 
 	/*
 	 * TODO: grab vginfo again, and compare vginfo->infos
diff --git a/lib/cache/lvmcache.h b/lib/cache/lvmcache.h
index f46fdfd12..3a75d9ca3 100644
--- a/lib/cache/lvmcache.h
+++ b/lib/cache/lvmcache.h
@@ -74,7 +74,7 @@ void lvmcache_destroy(struct cmd_context *cmd, int retain_orphans, int reset);
  */
 void lvmcache_force_next_label_scan(void);
 int lvmcache_label_scan(struct cmd_context *cmd);
-int lvmcache_label_refresh_for_vg(struct cmd_context *cmd, const char *vgname, const char *vgid);
+int lvmcache_label_rescan_vg(struct cmd_context *cmd, const char *vgname, const char *vgid);
 
 /* Add/delete a device */
 struct lvmcache_info *lvmcache_add(struct labeller *labeller, const char *pvid,
diff --git a/lib/cache/lvmetad.c b/lib/cache/lvmetad.c
index 51e813d31..86a2caced 100644
--- a/lib/cache/lvmetad.c
+++ b/lib/cache/lvmetad.c
@@ -1766,7 +1766,7 @@ static int _lvmetad_pvscan_single(struct metadata_area *mda, void *baton)
 	struct volume_group *vg;
 
 	if (mda_is_ignored(mda) ||
-	    !(vg = mda->ops->vg_read(b->fid, "", mda, NULL, NULL)))
+	    !(vg = mda->ops->vg_read(b->fid, "", mda, NULL, NULL, NULL)))
 		return 1;
 
 	/* FIXME Also ensure contents match etc. */
diff --git a/lib/format1/format1.c b/lib/format1/format1.c
index 6e7e888ff..816e2580f 100644
--- a/lib/format1/format1.c
+++ b/lib/format1/format1.c
@@ -180,6 +180,7 @@ out:
 static struct volume_group *_format1_vg_read(struct format_instance *fid,
 				     const char *vg_name,
 				     struct metadata_area *mda __attribute__((unused)),
+				     struct label_read_data *ld __attribute__((unused)),
 				     struct cached_vg_fmtdata **vg_fmtdata __attribute__((unused)),
 				     unsigned *use_previous_vg __attribute__((unused)))
 {
diff --git a/lib/format_pool/format_pool.c b/lib/format_pool/format_pool.c
index f8223a392..93214a179 100644
--- a/lib/format_pool/format_pool.c
+++ b/lib/format_pool/format_pool.c
@@ -101,6 +101,7 @@ static int _check_usp(const char *vgname, struct user_subpool *usp, int sp_count
 static struct volume_group *_pool_vg_read(struct format_instance *fid,
 					  const char *vg_name,
 					  struct metadata_area *mda __attribute__((unused)),
+					  struct label_read_data *ld __attribute__((unused)),
 					  struct cached_vg_fmtdata **vg_fmtdata __attribute__((unused)),
 					  unsigned *use_previous_vg __attribute__((unused)))
 {
diff --git a/lib/format_text/archiver.c b/lib/format_text/archiver.c
index c696ee832..aa448735e 100644
--- a/lib/format_text/archiver.c
+++ b/lib/format_text/archiver.c
@@ -320,7 +320,7 @@ struct volume_group *backup_read_vg(struct cmd_context *cmd,
 	}
 
 	dm_list_iterate_items(mda, &tf->metadata_areas_in_use) {
-		if (!(vg = mda->ops->vg_read(tf, vg_name, mda, NULL, NULL)))
+		if (!(vg = mda->ops->vg_read(tf, vg_name, mda, NULL, NULL, NULL)))
 			stack;
 		break;
 	}
diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c
index 86ee888ac..3755169ba 100644
--- a/lib/format_text/format-text.c
+++ b/lib/format_text/format-text.c
@@ -515,6 +515,7 @@ static int _raw_holds_vgname(struct format_instance *fid,
 static struct volume_group *_vg_read_raw_area(struct format_instance *fid,
 					      const char *vgname,
 					      struct device_area *area,
+					      struct label_read_data *ld,
 					      struct cached_vg_fmtdata **vg_fmtdata,
 					      unsigned *use_previous_vg,
 					      int precommitted)
@@ -526,7 +527,7 @@ static struct volume_group *_vg_read_raw_area(struct format_instance *fid,
 	char *desc;
 	uint32_t wrap = 0;
 
-	if (!(mdah = raw_read_mda_header(fid->fmt, area, NULL)))
+	if (!(mdah = raw_read_mda_header(fid->fmt, area, ld)))
 		goto_out;
 
 	if (!(rlocn = _find_vg_rlocn(area, mdah, vgname, &precommitted))) {
@@ -543,7 +544,7 @@ static struct volume_group *_vg_read_raw_area(struct format_instance *fid,
 		goto out;
 	}
 
-	vg = text_read_metadata(fid, NULL, vg_fmtdata, use_previous_vg, area->dev,
+	vg = text_read_metadata(fid, area->dev, NULL, ld, vg_fmtdata, use_previous_vg,
 				(off_t) (area->start + rlocn->offset),
 				(uint32_t) (rlocn->size - wrap),
 				(off_t) (area->start + MDA_HEADER_SIZE),
@@ -573,6 +574,7 @@ static struct volume_group *_vg_read_raw_area(struct format_instance *fid,
 static struct volume_group *_vg_read_raw(struct format_instance *fid,
 					 const char *vgname,
 					 struct metadata_area *mda,
+					 struct label_read_data *ld,
 					 struct cached_vg_fmtdata **vg_fmtdata,
 					 unsigned *use_previous_vg)
 {
@@ -582,7 +584,7 @@ static struct volume_group *_vg_read_raw(struct format_instance *fid,
 	if (!dev_open_readonly(mdac->area.dev))
 		return_NULL;
 
-	vg = _vg_read_raw_area(fid, vgname, &mdac->area, vg_fmtdata, use_previous_vg, 0);
+	vg = _vg_read_raw_area(fid, vgname, &mdac->area, ld, vg_fmtdata, use_previous_vg, 0);
 
 	if (!dev_close(mdac->area.dev))
 		stack;
@@ -593,6 +595,7 @@ static struct volume_group *_vg_read_raw(struct format_instance *fid,
 static struct volume_group *_vg_read_precommit_raw(struct format_instance *fid,
 						   const char *vgname,
 						   struct metadata_area *mda,
+						   struct label_read_data *ld,
 						   struct cached_vg_fmtdata **vg_fmtdata,
 						   unsigned *use_previous_vg)
 {
@@ -602,7 +605,7 @@ static struct volume_group *_vg_read_precommit_raw(struct format_instance *fid,
 	if (!dev_open_readonly(mdac->area.dev))
 		return_NULL;
 
-	vg = _vg_read_raw_area(fid, vgname, &mdac->area, vg_fmtdata, use_previous_vg, 1);
+	vg = _vg_read_raw_area(fid, vgname, &mdac->area, ld, vg_fmtdata, use_previous_vg, 1);
 
 	if (!dev_close(mdac->area.dev))
 		stack;
@@ -917,6 +920,7 @@ static struct volume_group *_vg_read_file_name(struct format_instance *fid,
 static struct volume_group *_vg_read_file(struct format_instance *fid,
 					  const char *vgname,
 					  struct metadata_area *mda,
+					  struct label_read_data *ld,
 					  struct cached_vg_fmtdata **vg_fmtdata,
 					  unsigned *use_previous_vg __attribute__((unused)))
 {
@@ -928,6 +932,7 @@ static struct volume_group *_vg_read_file(struct format_instance *fid,
 static struct volume_group *_vg_read_precommit_file(struct format_instance *fid,
 						    const char *vgname,
 						    struct metadata_area *mda,
+					  	    struct label_read_data *ld,
 						    struct cached_vg_fmtdata **vg_fmtdata,
 						    unsigned *use_previous_vg __attribute__((unused)))
 {
@@ -1293,7 +1298,7 @@ static int _scan_raw(const struct format_type *fmt, const char *vgname __attribu
 
 		/* TODO: caching as in read_metadata_location() (trigger this code?) */
 		if (read_metadata_location(fmt, mdah, NULL, &rl->dev_area, &vgsummary, NULL)) {
-			vg = _vg_read_raw_area(&fid, vgsummary.vgname, &rl->dev_area, NULL, NULL, 0);
+			vg = _vg_read_raw_area(&fid, vgsummary.vgname, &rl->dev_area, NULL, NULL, NULL, 0);
 			if (vg)
 				lvmcache_update_vg(vg, 0);
 		}
diff --git a/lib/format_text/import-export.h b/lib/format_text/import-export.h
index a23a15c8f..2610a39b5 100644
--- a/lib/format_text/import-export.h
+++ b/lib/format_text/import-export.h
@@ -71,10 +71,11 @@ struct volume_group *text_read_metadata_file(struct format_instance *fid,
 					 const char *file,
 					 time_t *when, char **desc);
 struct volume_group *text_read_metadata(struct format_instance *fid,
+				       struct device *dev,
 				       const char *file,
+				       struct label_read_data *ld,
 				       struct cached_vg_fmtdata **vg_fmtdata,
 				       unsigned *use_previous_vg,
-				       struct device *dev,
 				       off_t offset, uint32_t size,
 				       off_t offset2, uint32_t size2,
 				       checksum_fn_t checksum_fn,
diff --git a/lib/format_text/import.c b/lib/format_text/import.c
index d7d707aa1..7dac1b86e 100644
--- a/lib/format_text/import.c
+++ b/lib/format_text/import.c
@@ -125,10 +125,11 @@ struct cached_vg_fmtdata {
 };
 
 struct volume_group *text_read_metadata(struct format_instance *fid,
+				       struct device *dev,
 				       const char *file,
+				       struct label_read_data *ld,
 				       struct cached_vg_fmtdata **vg_fmtdata,
 				       unsigned *use_previous_vg,
-				       struct device *dev,
 				       off_t offset, uint32_t size,
 				       off_t offset2, uint32_t size2,
 				       checksum_fn_t checksum_fn,
@@ -138,6 +139,7 @@ struct volume_group *text_read_metadata(struct format_instance *fid,
 	struct volume_group *vg = NULL;
 	struct dm_config_tree *cft;
 	struct text_vg_version_ops **vsn;
+	char *buf_async = NULL;
 	int skip_parse;
 
 	/*
@@ -168,12 +170,32 @@ struct volume_group *text_read_metadata(struct format_instance *fid,
 		     ((*vg_fmtdata)->cached_mda_checksum == checksum) &&
 		     ((*vg_fmtdata)->cached_mda_size == (size + size2));
 
+	if (ld) {
+		if (ld->buf_len >= (offset + size))
+			buf_async = ld->buf;
+		else {
+			/*
+			 * Needs data beyond the end of the async read buffer.
+			 * Will do a new synchronous read to get the data.
+			 * (ASYNC_SCAN_SIZE could also be made larger.)
+			 */
+			log_debug_metadata("async read buffer for %s too small %u for metadata offset %llu size %u",
+					   dev_name(dev), ld->buf_len, (unsigned long long)offset, size);
+			buf_async = NULL;
+		}
+	}
+
 	if (dev) {
-		log_debug_metadata("Reading metadata from %s at %llu size %d (+%d)",
-				   dev_name(dev), (unsigned long long)offset,
-				   size, size2);
+		if (buf_async)
+			log_debug_metadata("Copying metadata for %s at %llu size %d (+%d)",
+					   dev_name(dev), (unsigned long long)offset,
+					   size, size2);
+		else
+			log_debug_metadata("Reading metadata from %s at %llu size %d (+%d)",
+				   	   dev_name(dev), (unsigned long long)offset,
+				           size, size2);
 
-		if (!config_file_read_fd(cft, dev, NULL, offset, size,
+		if (!config_file_read_fd(cft, dev, buf_async, offset, size,
 					 offset2, size2, checksum_fn, checksum,
 					 skip_parse, 1)) {
 			/* FIXME: handle errors */
@@ -225,7 +247,7 @@ struct volume_group *text_read_metadata_file(struct format_instance *fid,
 					 const char *file,
 					 time_t *when, char **desc)
 {
-	return text_read_metadata(fid, file, NULL, NULL, NULL,
+	return text_read_metadata(fid, NULL, file, NULL, NULL, NULL,
 				 (off_t)0, 0, (off_t)0, 0,
 				 NULL,
 				 0,
diff --git a/lib/label/label.c b/lib/label/label.c
index f371c3588..77b498f3f 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -25,6 +25,8 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+static DM_LIST_INIT(label_read_list);
+
 /* FIXME Allow for larger labels?  Restricted to single sector currently */
 
 /*
@@ -447,6 +449,31 @@ struct label *label_create(struct labeller *labeller)
 	return label;
 }
 
+static void _free_label_read_list(int do_close)
+{
+	struct label_read_data *ld, *ld2;
+
+	dm_list_iterate_items_safe(ld, ld2, &label_read_list) {
+		dm_list_del(&ld->list);
+		if (do_close)
+			dev_close(ld->dev);
+		if (ld->buf)
+			free(ld->buf);
+		free(ld);
+	}
+}
+
+struct label_read_data *get_label_read_data(struct cmd_context *cmd, struct device *dev)
+{
+	struct label_read_data *ld;
+
+	dm_list_iterate_items(ld, &label_read_list) {
+		if (ld->dev == dev)
+			return ld;
+	}
+	return NULL;
+}
+
 /*
  * Start label aio read on a device.
  */
@@ -582,22 +609,22 @@ static int _label_read_async_process(struct cmd_context *cmd, struct label_read_
 #define MAX_ASYNC_EVENTS 1024
 
 /*
- * label_scan iterates over all visible devices, looking
- * for any that belong to lvm, and fills lvmcache with
- * basic info about them.  It's main job is to prepare
- * for subsequent vg_reads.  vg_read(vgname) needs to
- * know which devices/locations to read metadata from
- * for the given vg name.  The label_scan has scanned
- * all devices and saved info in lvmcache about:
- * the device, the mda locations on that device,
- * and the vgname referenced in those mdas.  So,
- * vg_read(vgname) can map the vgname to a set of
- * mda locations it needs to read to get the metadata.
+ * label_scan run at the start of a command iterates over all visible devices,
+ * looking for any that belong to lvm, and fills lvmcache with basic info about
+ * them.  It's main job is to prepare for subsequent vg_reads.  vg_read(vgname)
+ * needs to know which devices/locations to read metadata from for the given vg
+ * name.  The label_scan has scanned all devices and saved info in lvmcache
+ * about: the device, the mda locations on that device, and the vgname
+ * referenced in those mdas.  So, vg_read(vgname) can map the vgname to a the
+ * subset of devices it needs to read for that VG.
+ */
+
+/*
+ * Scan labels/metadata for all devices (async)
  */
 
 int label_scan_async(struct cmd_context *cmd)
 {
-	struct dm_list label_read_list;
 	struct label_read_data *ld, *ld2;
 	struct dev_iter *iter;
 	struct device *dev;
@@ -611,7 +638,7 @@ int label_scan_async(struct cmd_context *cmd)
 	int dev_count = 0;
 	int error;
 
-	dm_list_init(&label_read_list);
+	_free_label_read_list(0);
 
 	/*
 	 * "buf" is the buffer into which the first ASYNC_SCAN_SIZE bytes
@@ -652,7 +679,7 @@ int label_scan_async(struct cmd_context *cmd)
 
 	dev_cache_full_scan(cmd->full_filter);
 
-	log_debug_devs("Scanning labels async");
+	log_debug_devs("Scanning all labels async");
 
 	if (!(iter = dev_iter_create(cmd->full_filter, 0))) {
 		log_error("Scanning labels failed to get devices.");
@@ -780,13 +807,8 @@ int label_scan_async(struct cmd_context *cmd)
 
 	io_destroy(aio_ctx);
 
-	dm_list_iterate_items_safe(ld, ld2, &label_read_list) {
-		dm_list_del(&ld->list);
+	dm_list_iterate_items(ld, &label_read_list)
 		dev_close(ld->dev);
-		if (ld->buf)
-			free(ld->buf);
-		free(ld);
-	}
 
 	log_debug_devs("Scanned %d labels async", dev_count);
 	return 1;
@@ -808,6 +830,148 @@ bad:
 	return 0;
 }
 
+/*
+ * Rescan labels/metadata for select devices (async)
+ * (devs from a specific VG)
+ */
+
+int label_rescan_async(struct cmd_context *cmd, struct dm_list *devs)
+{
+	struct dm_list tmp_label_read_list;
+	struct label_read_data *ld, *ld2;
+	struct device_list *devl;
+	struct device *dev;
+	io_context_t aio_ctx;
+	int need_wait_count;
+	int need_process_count;
+	int dev_count = 0;
+	int error;
+
+	dm_list_init(&tmp_label_read_list);
+
+	memset(&aio_ctx, 0, sizeof(io_context_t));
+
+	error = io_setup(MAX_ASYNC_EVENTS, &aio_ctx);
+	if (error < 0) {
+		log_debug_devs("async io setup error %d, reverting to sync io.", error);
+		return_0;
+	}
+
+	log_debug_devs("Scanning labels for VG devs async");
+
+	dm_list_iterate_items(devl, devs) {
+		dev = devl->dev;
+
+		if (!(ld = get_label_read_data(cmd, dev))) {
+			log_warn("WARNING: label rescan cannot find dev %s", dev_name(dev));
+			continue;
+		}
+
+		/* Temporarily move structs being reread onto local list. */
+		dm_list_del(&ld->list);
+		dm_list_add(&tmp_label_read_list, &ld->list);
+
+		if (!dev_open_readonly(ld->dev)) {
+			log_debug_devs("Reading label skipped can't open %s", dev_name(dev));
+			continue;
+		}
+
+		ld->try_sync = 0;
+		ld->read_done = 0;
+		ld->process_done = 0;
+
+		if (!_label_read_async_start(cmd, aio_ctx, ld))
+			ld->try_sync = 1;
+		else
+			log_debug_devs("Reading sectors from device %s async", dev_name(ld->dev));
+
+		dev_count++;
+	}
+
+	/*
+	 * Try a synchronous read for any dev where aio couldn't be submitted.
+	 */
+	dm_list_iterate_items(ld, &tmp_label_read_list) {
+		if (ld->try_sync) {
+			log_debug_devs("Reading sectors from device %s trying sync", dev_name(ld->dev));
+
+			if (!dev_read(ld->dev, 0, ld->buf_len, ld->buf)) {
+				log_debug_devs("%s: Failed to read label area", dev_name(ld->dev));
+				ld->read_result = -1;
+			} else {
+				ld->read_result = ld->buf_len;
+			}
+			ld->read_done = 1;
+		}
+	}
+
+	/*
+	 * Reap the aio and process the results.
+	 */
+
+ check_aio:
+	need_wait_count = 0;
+	need_process_count = 0;
+
+	dm_list_iterate_items(ld, &tmp_label_read_list) {
+		if (!ld->read_done)
+			need_wait_count++;
+		else if (!ld->process_done)
+			need_process_count++;
+	}
+
+	/*
+	 * Process devices that have finished reading label sectors.
+	 * Processing includes sync i/o to read mda locations and vg metadata.
+	 *
+	 * FIXME: we shouldn't need to fully reprocess everything when rescanning.
+	 * lvmcache is already populated from the previous scan, and if nothing
+	 * has changed we don't need to repopulate it with the same data.
+	 * Do something like check the metadata checksum from previous label scan
+	 * and don't reprocess here if it's the same.
+	 */
+	if (need_process_count) {
+		dm_list_iterate_items(ld, &tmp_label_read_list) {
+			if (!ld->read_done || ld->process_done)
+				continue;
+			log_debug_devs("Parsing label and data from device %s", dev_name(ld->dev));
+			_label_read_async_process(cmd, ld);
+			ld->process_done = 1;
+		}
+	}
+
+	/*
+	 * Wait for more devices to finish reading label sectors.
+	 */
+	if (need_wait_count) {
+		if (_label_read_async_wait(cmd, aio_ctx, need_wait_count))
+			goto check_aio;
+
+		/* TODO: handle this error */
+		/* an error getting aio events, should we fall back
+		   to doing sync dev_read() on any that aren't done? */
+		log_error(INTERNAL_ERROR "aio getevents error");
+	}
+
+	io_destroy(aio_ctx);
+
+	dm_list_iterate_items(ld, &tmp_label_read_list)
+		dev_close(ld->dev);
+
+	/* Move structs being reread back to normal list */
+	dm_list_iterate_items_safe(ld, ld2, &tmp_label_read_list) {
+		dm_list_del(&ld->list);
+		dm_list_add(&label_read_list, &ld->list);
+	}
+
+	log_debug_devs("Scanned %d labels for VG devs async", dev_count);
+	return 1;
+}
+
+/*
+ * Read label/metadata for one dev (sync)
+ */
+
 static int _label_read_sync(struct cmd_context *cmd, struct device *dev)
 {
 	char scanbuf[LABEL_SCAN_SIZE] __attribute__((aligned(8)));
@@ -856,8 +1020,9 @@ static int _label_read_sync(struct cmd_context *cmd, struct device *dev)
 }
 
 /*
- * Read and process device labels/data without aio.
+ * Scan labels/metadata for all devices (sync)
  */
+
 int label_scan_sync(struct cmd_context *cmd)
 {
 	struct dev_iter *iter;
@@ -865,11 +1030,13 @@ int label_scan_sync(struct cmd_context *cmd)
 	int dev_count = 0;
 	struct lvmcache_info *info;
 
+	_free_label_read_list(0);
+
 	log_debug_devs("Finding devices to scan");
 
 	dev_cache_full_scan(cmd->full_filter);
 
-	log_very_verbose("Scanning labels sync");
+	log_very_verbose("Scanning all labels sync");
 
 	if (!(iter = dev_iter_create(cmd->full_filter, 0))) {
 		log_error("Scanning labels failed to get devices.");
@@ -900,3 +1067,33 @@ int label_scan_sync(struct cmd_context *cmd)
 	return 1;
 }
 
+/*
+ * Rescan labels/metadata for select devices (sync)
+ * (devs from a specific VG)
+ */
+
+int label_rescan_sync(struct cmd_context *cmd, struct dm_list *devs)
+{
+	struct device_list *devl;
+	int dev_count = 0;
+
+	log_debug_devs("Scanning labels for VG devs sync");
+
+	dm_list_iterate_items(devl, devs) {
+		if (!dev_open_readonly(devl->dev)) {
+			log_debug_devs("Reading label skipped can't open %s", dev_name(devl->dev));
+			continue;
+		}
+
+		_label_read_sync(cmd, devl->dev);
+
+		if (!dev_close(devl->dev))
+			stack;
+
+		dev_count++;
+	}
+
+	log_very_verbose("Scanned %d labels for VG devs sync", dev_count);
+	return 1;
+}
+
diff --git a/lib/label/label.h b/lib/label/label.h
index ebd0afb44..26424e5bd 100644
--- a/lib/label/label.h
+++ b/lib/label/label.h
@@ -131,5 +131,8 @@ void label_destroy(struct label *label);
 
 int label_scan_async(struct cmd_context *cmd);
 int label_scan_sync(struct cmd_context *cmd);
+int label_rescan_async(struct cmd_context *cmd, struct dm_list *devs);
+int label_rescan_sync(struct cmd_context *cmd, struct dm_list *devs);
+struct label_read_data *get_label_read_data(struct cmd_context *cmd, struct device *dev);
 
 #endif
diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index 895519d89..4ea5aca27 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -34,6 +34,7 @@
 #include "lvmlockd.h"
 #include "time.h"
 #include "lvmnotify.h"
+#include "label.h"
 
 #include <math.h>
 #include <sys/param.h>
@@ -3851,7 +3852,7 @@ static struct volume_group *_vg_read(struct cmd_context *cmd,
 	 */
 	log_debug_metadata("Reading VG rereading labels for %s", vgname);
 
-	if (!lvmcache_label_refresh_for_vg(cmd, vgname, vgid)) {
+	if (!lvmcache_label_rescan_vg(cmd, vgname, vgid)) {
 		/* The VG wasn't found, so force a full label scan. */
 		lvmcache_force_next_label_scan();
 		lvmcache_label_scan(cmd);
@@ -3901,15 +3902,16 @@ static struct volume_group *_vg_read(struct cmd_context *cmd,
 	inconsistent_mda_count=0;
 	dm_list_iterate_items(mda, &fid->metadata_areas_in_use) {
 		struct device *mda_dev = mda_get_device(mda);
+		struct label_read_data *ld;
 
 		use_previous_vg = 0;
 
-		log_debug_metadata("Reading VG %s from mda on %s", vgname, dev_name(mda_dev));
+		log_debug_metadata("Reading VG %s from %s", vgname, dev_name(mda_dev));
 
-		if ((use_precommitted &&
-		     !(vg = mda->ops->vg_read_precommit(fid, vgname, mda, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg) ||
-		    (!use_precommitted &&
-		     !(vg = mda->ops->vg_read(fid, vgname, mda, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg)) {
+		ld = get_label_read_data(cmd, mda_dev);
+
+		if ((use_precommitted && !(vg = mda->ops->vg_read_precommit(fid, vgname, mda, ld, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg) ||
+		    (!use_precommitted && !(vg = mda->ops->vg_read(fid, vgname, mda, ld, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg)) {
 			inconsistent = 1;
 			vg_fmtdata = NULL;
 			continue;
@@ -4099,9 +4101,9 @@ static struct volume_group *_vg_read(struct cmd_context *cmd,
 			use_previous_vg = 0;
 
 			if ((use_precommitted &&
-			     !(vg = mda->ops->vg_read_precommit(fid, vgname, mda, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg) ||
+			     !(vg = mda->ops->vg_read_precommit(fid, vgname, mda, NULL, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg) ||
 			    (!use_precommitted &&
-			     !(vg = mda->ops->vg_read(fid, vgname, mda, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg)) {
+			     !(vg = mda->ops->vg_read(fid, vgname, mda, NULL, &vg_fmtdata, &use_previous_vg)) && !use_previous_vg)) {
 				inconsistent = 1;
 				vg_fmtdata = NULL;
 				continue;
diff --git a/lib/metadata/metadata.h b/lib/metadata/metadata.h
index a60780ef7..937945607 100644
--- a/lib/metadata/metadata.h
+++ b/lib/metadata/metadata.h
@@ -25,6 +25,8 @@
 #include "dev-cache.h"
 #include "lvm-string.h"
 #include "metadata-exported.h"
+#include "lvm-logging.h"
+#include "label.h"
 
 //#define MAX_STRIPES 128U
 //#define SECTOR_SHIFT 9L
@@ -79,11 +81,13 @@ struct metadata_area_ops {
 	struct volume_group *(*vg_read) (struct format_instance * fi,
 					 const char *vg_name,
 					 struct metadata_area * mda,
+					 struct label_read_data *ld,
 					 struct cached_vg_fmtdata **vg_fmtdata,
 					 unsigned *use_previous_vg);
 	struct volume_group *(*vg_read_precommit) (struct format_instance * fi,
 					 const char *vg_name,
 					 struct metadata_area * mda,
+					 struct label_read_data *ld,
 					 struct cached_vg_fmtdata **vg_fmtdata,
 					 unsigned *use_previous_vg);
 	/*