lib/cache/lvmcache.c          |  24 +++++++++

 lib/cache/lvmcache.h          |   4 ++

 lib/device/bcache-utils.c     |  15 ++++++

 lib/device/bcache.h           |   1 +

 lib/format_text/format-text.c |  16 +++++-

 lib/format_text/layout.h      |   2 +-

 lib/format_text/text_label.c  |   2 +-

 lib/label/label.c             |   5 ++

 lib/label/label.h             |   1 +

 lib/metadata/metadata.c       | 117 +++++++++++++++++++++++++++++++++++++++++-

 lib/metadata/metadata.h       |   4 +-

 11 files changed, 186 insertions(+), 5 deletions(-)

diff --git a/lib/cache/lvmcache.c b/lib/cache/lvmcache.c

index b6a02b0..5b8dce8 100644

--- a/lib/cache/lvmcache.c

+++ b/lib/cache/lvmcache.c

@@ -3068,3 +3068,27 @@ uint64_t lvmcache_max_metadata_size(void)

 	return _max_metadata_size;

 }

+void lvmcache_get_mdas(struct cmd_context *cmd,

+		       const char *vgname, const char *vgid,

+                       struct dm_list *mda_list)

+{

+	struct lvmcache_vginfo *vginfo;

+	struct lvmcache_info *info;

+	struct mda_list *mdal;

+	struct metadata_area *mda, *mda2;

+

+	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, vgid))) {

+		log_error(INTERNAL_ERROR "lvmcache_get_mdas no vginfo %s", vgname);

+		return;

+	}

+

+	dm_list_iterate_items(info, &vginfo->infos) {

+		dm_list_iterate_items_safe(mda, mda2, &info->mdas) {

+			if (!(mdal = dm_zalloc(sizeof(*mdal))))

+				continue;

+			mdal->mda = mda;

+			dm_list_add(mda_list, &mdal->list);

+		}

+	}

+}

+

diff --git a/lib/cache/lvmcache.h b/lib/cache/lvmcache.h

index f436785..541e8be 100644

--- a/lib/cache/lvmcache.h

+++ b/lib/cache/lvmcache.h

@@ -228,4 +228,8 @@ void lvmcache_drop_saved_vgid(const char *vgid);

 uint64_t lvmcache_max_metadata_size(void);

 void lvmcache_save_metadata_size(uint64_t val);

+void lvmcache_get_mdas(struct cmd_context *cmd,

+                       const char *vgname, const char *vgid,

+                       struct dm_list *mda_list);

+

 #endif

diff --git a/lib/device/bcache-utils.c b/lib/device/bcache-utils.c

index a533a66..2f0b01d 100644

--- a/lib/device/bcache-utils.c

+++ b/lib/device/bcache-utils.c

@@ -79,6 +79,21 @@ bool bcache_read_bytes(struct bcache *cache, int fd, uint64_t start, size_t len,

 	return true;

 }

+bool bcache_invalidate_bytes(struct bcache *cache, int fd, uint64_t start, size_t len)

+{

+	block_address bb, be;

+	bool result = true;

+

+	byte_range_to_block_range(cache, start, len, &bb, &be);

+

+	for (; bb != be; bb++) {

+		if (!bcache_invalidate(cache, fd, bb))

+			result = false;

+	}

+

+	return result;

+}

+

 //----------------------------------------------------------------

 // Writing bytes and zeroing bytes are very similar, so we factor out

diff --git a/lib/device/bcache.h b/lib/device/bcache.h

index f9067f7..3e7a168 100644

--- a/lib/device/bcache.h

+++ b/lib/device/bcache.h

@@ -163,6 +163,7 @@ bool bcache_read_bytes(struct bcache *cache, int fd, uint64_t start, size_t len,

 bool bcache_write_bytes(struct bcache *cache, int fd, uint64_t start, size_t len, void *data);

 bool bcache_zero_bytes(struct bcache *cache, int fd, uint64_t start, size_t len);

 bool bcache_set_bytes(struct bcache *cache, int fd, uint64_t start, size_t len, uint8_t val);

+bool bcache_invalidate_bytes(struct bcache *cache, int fd, uint64_t start, size_t len);

 void bcache_set_last_byte(struct bcache *cache, int fd, uint64_t offset, int sector_size);

 void bcache_unset_last_byte(struct bcache *cache, int fd);

diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c

index 6f5d739..75d7fcd 100644

--- a/lib/format_text/format-text.c

+++ b/lib/format_text/format-text.c

@@ -1199,6 +1199,7 @@ static int _scan_file(const struct format_type *fmt, const char *vgname)

 }

 int read_metadata_location_summary(const struct format_type *fmt,

+		    struct metadata_area *mda,

 		    struct mda_header *mdah, int primary_mda, struct device_area *dev_area,

 		    struct lvmcache_vgsummary *vgsummary, uint64_t *mda_free_sectors)

 {

@@ -1251,6 +1252,19 @@ int read_metadata_location_summary(const struct format_type *fmt,

 		return 0;

 	}

+	/*

+	 * This function is used to read the vg summary during label scan.

+	 * Save the text start location and checksum during scan.  After the VG

+	 * lock is acquired in vg_read, we can reread the mda_header, and

+	 * compare rlocn->offset,checksum to what was saved during scan.  If

+	 * unchanged, it means that the metadata was not changed between scan

+	 * and the read.

+	 */

+	if (mda) {

+		mda->scan_text_offset = rlocn->offset;

+		mda->scan_text_checksum = rlocn->checksum;

+	}

+

 	/* We found a VG - now check the metadata */

 	if (rlocn->offset + rlocn->size > mdah->size)

 		wrap = (uint32_t) ((rlocn->offset + rlocn->size) - mdah->size);

@@ -1374,7 +1388,7 @@ static int _scan_raw(const struct format_type *fmt, const char *vgname __attribu

 			continue;

 		}

-		if (read_metadata_location_summary(fmt, mdah, 0, &rl->dev_area, &vgsummary, NULL)) {

+		if (read_metadata_location_summary(fmt, NULL, mdah, 0, &rl->dev_area, &vgsummary, NULL)) {

 			vg = _vg_read_raw_area(&fid, vgsummary.vgname, &rl->dev_area, NULL, NULL, 0, 0);

 			if (vg) {

 				lvmcache_update_vg(vg, 0);

diff --git a/lib/format_text/layout.h b/lib/format_text/layout.h

index 2671bbf..4601952 100644

--- a/lib/format_text/layout.h

+++ b/lib/format_text/layout.h

@@ -104,7 +104,7 @@ struct mda_context {

 #define MDA_SIZE_MIN (8 * (unsigned) lvm_getpagesize())

 #define MDA_ORIGINAL_ALIGNMENT 512	/* Original alignment used for start of VG metadata content */

-int read_metadata_location_summary(const struct format_type *fmt, struct mda_header *mdah, int primary_mda, 

+int read_metadata_location_summary(const struct format_type *fmt, struct metadata_area *mda, struct mda_header *mdah, int primary_mda, 

 		    struct device_area *dev_area, struct lvmcache_vgsummary *vgsummary,

 		    uint64_t *mda_free_sectors);

diff --git a/lib/format_text/text_label.c b/lib/format_text/text_label.c

index 7d10e06..fc8294e 100644

--- a/lib/format_text/text_label.c

+++ b/lib/format_text/text_label.c

@@ -345,7 +345,7 @@ static int _read_mda_header_and_metadata(struct metadata_area *mda, void *baton)

 		return 1;

 	}

-	if (!read_metadata_location_summary(fmt, mdah, mda_is_primary(mda), &mdac->area,

+	if (!read_metadata_location_summary(fmt, mda, mdah, mda_is_primary(mda), &mdac->area,

 					    &vgsummary, &mdac->free_sectors)) {

 		if (vgsummary.zero_offset)

 			return 1;

diff --git a/lib/label/label.c b/lib/label/label.c

index 70b7934..8a4b662 100644

--- a/lib/label/label.c

+++ b/lib/label/label.c

@@ -1418,6 +1418,11 @@ bool dev_write_bytes(struct device *dev, uint64_t start, size_t len, void *data)

 	return true;

 }

+bool dev_invalidate_bytes(struct device *dev, uint64_t start, size_t len)

+{

+	return bcache_invalidate_bytes(scan_bcache, dev->bcache_fd, start, len);

+}

+

 bool dev_write_zeros(struct device *dev, uint64_t start, size_t len)

 {

 	if (test_mode())

diff --git a/lib/label/label.h b/lib/label/label.h

index 42c9946..ea29c84 100644

--- a/lib/label/label.h

+++ b/lib/label/label.h

@@ -128,6 +128,7 @@ bool dev_read_bytes(struct device *dev, uint64_t start, size_t len, void *data);

 bool dev_write_bytes(struct device *dev, uint64_t start, size_t len, void *data);

 bool dev_write_zeros(struct device *dev, uint64_t start, size_t len);

 bool dev_set_bytes(struct device *dev, uint64_t start, size_t len, uint8_t val);

+bool dev_invalidate_bytes(struct device *dev, uint64_t start, size_t len);

 void dev_set_last_byte(struct device *dev, uint64_t offset);

 void dev_unset_last_byte(struct device *dev);

diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c

index d448fd9..39f10fe 100644

--- a/lib/metadata/metadata.c

+++ b/lib/metadata/metadata.c

@@ -33,6 +33,8 @@

 #include "lvmlockd.h"

 #include "time.h"

 #include "lvmnotify.h"

+#include "format_text/format-text.h"

+#include "format_text/layout.h"

 #include <math.h>

 #include <sys/param.h>

@@ -3760,6 +3762,118 @@ out:

 	return r;

 }

+/*

+ * Reread an mda_header.  If the text offset is the same as was seen and saved

+ * by label scan, it means the metadata is unchanged and we do not need to

+ * reread metadata.

+ *

+ * This is used to ensure that the metadata seen during scan still matches

+ * what's on disk.  If the scan data still matches what's on disk we don't

+ * need to reread the metadata from disk.  When we read the metadata from

+ * bcache it may come from the cache or from disk again if the cache has

+ * dropped it.

+ */

+

+static bool _scan_text_mismatch(struct cmd_context *cmd, const char *vgname, const char *vgid)

+{

+	struct dm_list mda_list;

+	struct mda_list *mdal, *safe;

+	struct metadata_area *mda;

+	struct mda_context *mdac;

+	struct device_area *area;

+	struct mda_header *mdah;

+	struct raw_locn *rlocn;

+	struct device *dev;

+	bool ret = true;

+

+	/*

+	 * if cmd->can_use_one_scan, check one mda_header is unchanged,

+	 * else check that all mda_headers are unchanged.

+	 */

+

+	dm_list_init(&mda_list);

+

+	lvmcache_get_mdas(cmd, vgname, vgid, &mda_list);

+

+	dm_list_iterate_items(mdal, &mda_list) {

+		mda = mdal->mda;

+

+		if (!mda->scan_text_offset)

+			continue;

+

+		if (!mda_is_primary(mda))

+			continue;

+

+		if (!(dev = mda_get_device(mda))) {

+			log_debug("rescan for text mismatch - no mda dev");

+			goto out;

+		}

+

+		mdac = mda->metadata_locn;

+		area = &mdac->area;

+

+		/*

+		 * Invalidate mda_header in bcache so it will be reread from disk.

+		 */

+		if (!dev_invalidate_bytes(dev, 4096, 512)) {

+			log_debug("rescan for text mismatch - cannot invalidate");

+			goto out;

+		}

+

+		if (!(mdah = raw_read_mda_header(cmd->fmt, area, 1))) {

+			log_debug("rescan for text mismatch - no mda header");

+			goto out;

+		}

+

+		rlocn = mdah->raw_locns;

+

+		if (rlocn->checksum != mda->scan_text_checksum) {

+			log_debug("rescan for text checksum mismatch on %s - now %x prev %x offset now %llu prev %llu",

+				  dev_name(dev),

+				  rlocn->checksum, mda->scan_text_checksum,

+				  (unsigned long long)rlocn->offset,

+				  (unsigned long long)mda->scan_text_offset);

+		} else if (rlocn->offset != mda->scan_text_offset) {

+			log_debug("rescan for text offset mismatch on %s - now %llu prev %llu checksum %x",

+				  dev_name(dev),

+				  (unsigned long long)rlocn->offset,

+				  (unsigned long long)mda->scan_text_offset,

+				  rlocn->checksum);

+		} else {

+			/* the common case where fields match and no rescan needed */

+			ret = false;

+		}

+

+		dm_pool_free(cmd->mem, mdah);

+

+		/* For can_use_one_scan commands, return result from checking one mda. */

+		if (cmd->can_use_one_scan)

+			goto out;

+

+		/* For other commands, return mismatch immediately. */

+		if (ret)

+			goto_out;

+	}

+

+	if (ret) {

+		/* shouldn't happen */

+		log_debug("rescan for text mismatch - no mdas");

+		goto out;

+	}

+out:

+	if (!ret)

+		log_debug("rescan skipped - unchanged offset %llu checksum %x",

+			  (unsigned long long)mda->scan_text_offset,

+			  mda->scan_text_checksum);

+

+	dm_list_iterate_items_safe(mdal, safe, &mda_list) {

+		dm_list_del(&mdal->list);

+		free(mdal);

+	}

+

+	return ret;

+}

+

 /* Caller sets consistent to 1 if it's safe for vg_read_internal to correct

  * inconsistent metadata on disk (i.e. the VG write lock is held).

  * This guarantees only consistent metadata is returned.

@@ -3904,7 +4018,8 @@ static struct volume_group *_vg_read(struct cmd_context *cmd,

 	 * lock is taken prior to the label scan, and still held here,

 	 * we can also skip the rescan in that case.

 	 */

-	if (!cmd->can_use_one_scan || lvmcache_scan_mismatch(cmd, vgname, vgid)) {

+	if (!cmd->can_use_one_scan ||

+	    lvmcache_scan_mismatch(cmd, vgname, vgid) || _scan_text_mismatch(cmd, vgname, vgid)) {

 		/* the skip rescan special case is for clvmd vg_read_by_vgid */

 		/* FIXME: this is not a warn flag, pass this differently */

 		if (warn_flags & SKIP_RESCAN)

diff --git a/lib/metadata/metadata.h b/lib/metadata/metadata.h

index f8083e5..96bbb56 100644

--- a/lib/metadata/metadata.h

+++ b/lib/metadata/metadata.h

@@ -173,6 +173,8 @@ struct metadata_area {

 	struct metadata_area_ops *ops;

 	void *metadata_locn;

 	uint32_t status;

+	uint64_t scan_text_offset; /* rlocn->offset seen during scan */

+	uint32_t scan_text_checksum; /* rlocn->checksum seen during scan */

 };

 struct metadata_area *mda_copy(struct dm_pool *mem,

 			       struct metadata_area *mda);

@@ -234,7 +236,7 @@ struct name_list {

 struct mda_list {

 	struct dm_list list;

-	struct device_area mda;

+	struct metadata_area *mda;

 };

 struct peg_list {