From dac2bfe6a4a901b91bf3c6c5ebf39ce5a14c8f20 Mon Sep 17 00:00:00 2001
From: Zdenek Kabelac <zkabelac@redhat.com>
Date: Thu, 23 May 2024 01:36:50 +0200
Subject: [PATCH] device_manager: add device_get_uuid

Function that is working with DM target is located within
lib/activate directory.

This function is able to use cached  dm_device_list when possible
to quickly resolve checks for device's UUID.

Function can fully replace get_dm_uuid_from_sysfs() and instead
of syscalls for open/read/close get the UUID with single ioctl.

When there is cached dm devs list, we can get many UUID from
a single syscall.
---
 lib/activate/activate.h    |  2 ++
 lib/activate/dev_manager.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lib/activate/activate.h b/lib/activate/activate.h
index e550ec5b0..ca8b6e695 100644
--- a/lib/activate/activate.h
+++ b/lib/activate/activate.h
@@ -109,6 +109,8 @@ int target_version(const char *target_name, uint32_t *maj,
 
 int get_device_list(const struct volume_group *vg, struct dm_list **devs,
 		    unsigned *devs_features);
+int device_get_uuid(struct cmd_context *cmd, int major, int minor,
+		    char *uuid_buf, size_t uuid_buf_size);
 
 int raid4_is_supported(struct cmd_context *cmd, const struct segment_type *segtype);
 int lvm_dm_prefix_check(int major, int minor, const char *prefix);
diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index 52766f58a..34fd49665 100644
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -880,6 +880,36 @@ int device_is_usable(struct cmd_context *cmd, struct device *dev, struct dev_usa
 	return r;
 }
 
+/* Read UUID from a given DM device into  buf_uuid */
+int device_get_uuid(struct cmd_context *cmd, int major, int minor,
+		    char *uuid_buf, size_t uuid_buf_size)
+{
+	struct dm_task *dmt;
+	struct dm_info info;
+	const char *uuid;
+	int r = 0;
+
+	if (cmd->cache_dm_devs) {
+		if (dm_device_list_find_by_dev(cmd->cache_dm_devs, major, minor, NULL, &uuid)) {
+			dm_strncpy(uuid_buf, uuid, uuid_buf_size);
+			return 1;
+		}
+		uuid_buf[0] = 0;
+		return 0;
+	}
+
+	if (!(dmt = _setup_task_run(DM_DEVICE_INFO, &info, NULL, NULL, NULL,
+				    major, minor, 0, 0, 0)))
+		return_0;
+
+	if (info.exists && (uuid = dm_task_get_uuid(dmt)))
+		r = dm_strncpy(uuid_buf, uuid, uuid_buf_size);
+
+	dm_task_destroy(dmt);
+
+	return r;
+}
+
 /*
  * If active LVs were activated by a version of LVM2 before 2.02.00 we must
  * perform additional checks to find them because they do not have the LVM-