From 28a0f08ce75626ac147d60f0653c87e436a77281 Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Wed, 16 Sep 2020 22:46:12 +0300
Subject: [PATCH] Add a very simple tool for calculating device offsets

---
 mon/simple-offsets.js | 53 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 mon/simple-offsets.js

diff --git a/mon/simple-offsets.js b/mon/simple-offsets.js
new file mode 100644
index 00000000..c2648696
--- /dev/null
+++ b/mon/simple-offsets.js
@@ -0,0 +1,53 @@
+// Simple tool to calculate journal and metadata offsets for a single device
+// Will be replaced by smarter tools in the future
+
+const child_process = require('child_process');
+
+async function run()
+{
+    const options = {
+        object_size: 128*1024,
+        bitmap_granularity: 4096,
+        journal_size: 16*1024*1024,
+        device_block_size: 4096,
+        journal_offset: 0,
+        device_size: 0,
+    };
+    for (let i = 2; i < process.argv.length; i++)
+    {
+        if (process.argv[i].substr(0, 2) == '--')
+        {
+            options[process.argv[i].substr(2)] = process.argv[i+1];
+            i++;
+        }
+    }
+    const device_size = Number(options.device_size || await system("blockdev --getsize64 "+options.device));
+    if (!device_size)
+    {
+        process.stderr.write('Failed to get device size\n');
+        process.exit(1);
+    }
+    options.journal_offset = Math.ceil(options.journal_offset/options.device_block_size)*options.device_block_size;
+    const meta_offset = options.journal_offset + Math.ceil(options.journal_size/options.device_block_size)*options.device_block_size;
+    const entries_per_block = Math.floor(options.device_block_size / (24 + options.object_size/options.bitmap_granularity/8));
+    const object_count = Math.floor((device_size-meta_offset)/options.object_size);
+    const meta_size = Math.ceil(object_count / entries_per_block) * options.device_block_size;
+    const data_offset = meta_offset + meta_size;
+    const meta_size_fmt = (meta_size > 1024*1024*1024 ? Math.round(meta_size/1024/1024/1024*100)/100+" GB"
+        : Math.round(meta_size/1024/1024*100)/100+" MB");
+    process.stdout.write(
+        `Metadata size: ${meta_size_fmt}\n`+
+        `Options for the OSD:\n`+
+        `    --journal_offset ${options.journal_offset}\n`+
+        `    --meta_offset ${meta_offset}\n`+
+        `    --data_offset ${data_offset}\n`+
+        (options.device_size ? `    --data_size ${device_size-data_offset}\n` : '')
+    );
+}
+
+function system(cmd)
+{
+    return new Promise((ok, no) => child_process.exec(cmd, { maxBuffer: 64*1024*1024 }, (err, stdout, stderr) => (err ? no(err) : ok(stdout))));
+}
+
+run().catch(console.error);