[lvm-devel] master - thin: activate layer pool aas read-only LV

[Zdenek Kabelac]

Gitweb:        https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=66f69e766e576692ea32328c1921acbacb69ed14
Commit:        66f69e766e576692ea32328c1921acbacb69ed14
Parent:        693215716bde963d03c1adbddc6ecd39a0ea256c
Author:        Zdenek Kabelac <zkabelac at redhat.com>
AuthorDate:    Sat Sep 14 01:08:14 2019 +0200
Committer:     Zdenek Kabelac <zkabelac at redhat.com>
CommitterDate: Tue Sep 17 13:16:50 2019 +0200

thin: activate layer pool aas read-only LV

When lvm2 is activating layered pool LV (to basically keep pool opened,
the other function used to be 'locking' be in sync with DM table)
use this LV in read-only mode - this prevents 'write' access into
data volume content of thin-pool.

Note: since EMPTY/unused thin-pool is created as 'public LV' for generic
use by any user who i.e. wish to maintain thin-pool and thins himself.
At this moment, thin-pool appears as writable LV.  As soon as the 1st.
thinLV is created, layer volume will appear is 'read-only' LV from this moment.
---
 WHATS_NEW                  |    1 +
 lib/activate/dev_manager.c |    5 +++++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/WHATS_NEW b/WHATS_NEW
index 37ce33b..81a73ef 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.03.06 - 
 ================================
+  Activate thin-pool layered volume as 'read-only' device.
   Ignore crypto devices with UUID signature CRYPT-SUBDEV.
   Enhance validation for thin and cache pool conversion and swapping.
   Improve internal removal of cached devices.
diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index c780dea..32fdcb9 100644
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -85,6 +85,11 @@ int read_only_lv(const struct logical_volume *lv, const struct lv_activate_opts
 	if (lv_is_raid_image(lv) || lv_is_raid_metadata(lv))
 		return 0; /* Keep RAID SubLvs writable */
 
+	if (!layer) {
+		if (lv_is_thin_pool(lv))
+			return 1;
+	}
+
 	return (laopts->read_only || !(lv->status & LVM_WRITE));
 }