Initial remote commit

misc_tools/test_corruption.py

@@ -0,0 +1,50 @@
+import struct
+
+# Group 0 inode table at block 1070
+# Virtual byte: 1070 * 4096 = 4,382,720
+# Physical byte via chunk translation:
+CHUNK = 128*512
+LV_START = 5120000*512
+BSIZE = 4096
+
+it_virt = 1070 * BSIZE
+group     = it_virt // (5*CHUNK)
+in_group  = it_virt % (5*CHUNK)
+chunk_idx = in_group // CHUNK
+intra     = in_group % CHUNK
+
+print(f'Group 0 inode table:')
+print(f'  Virtual byte:  {it_virt}')
+print(f'  Chunk group:   {group}')
+print(f'  Chunk index:   {chunk_idx} (4=metadata)')
+print(f'  Is metadata:   {chunk_idx == 4}')
+
+if chunk_idx != 4:
+    phys = LV_START + group*4*CHUNK + chunk_idx*CHUNK + intra
+    print(f'  Physical byte: {phys}')
+    with open('/dev/sda','rb') as f:
+        f.seek(phys)
+        data = f.read(256)
+    nonzero = sum(1 for b in data if b != 0)
+    print(f'  First inode nonzero bytes: {nonzero}/256')
+    print(f'  First 32 bytes: {data[:32].hex()}')
+else:
+    print(f'  In PERC metadata chunk - reads as zeros')
+
+# Check groups 0-15
+print()
+print('Checking which groups have inode tables in metadata chunks:')
+for g in range(20):
+    it_block = 1070 + g*512
+    it_virt  = it_block * BSIZE
+    in_group  = it_virt % (5*CHUNK)
+    chunk_idx = in_group // CHUNK
+    if chunk_idx == 4:
+        print(f'  Group {g:2d}: inode table in METADATA CHUNK (reads as zeros)')
+    else:
+        phys = LV_START + (it_virt//(5*CHUNK))*4*CHUNK + chunk_idx*CHUNK + (it_virt%CHUNK)
+        with open('/dev/sda','rb') as f:
+            f.seek(phys)
+            data = f.read(256)
+        nonzero = sum(1 for b in data if b != 0)
+        print(f'  Group {g:2d}: DATA chunk, nonzero={nonzero}/256')