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Re: [PATCH v11 07/11] qcow2_format.py: Dump bitmap table serialized entr


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH v11 07/11] qcow2_format.py: Dump bitmap table serialized entries
Date: Tue, 28 Jul 2020 13:02:34 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

17.07.2020 11:14, Andrey Shinkevich wrote:
Add bitmap table information to the QCOW2 metadata dump.

Bitmap name               bitmap-1
...
Bitmap table   type            offset                   size
0              serialized      4718592                  65536
1              serialized      4294967296               65536
2              serialized      5348033147437056         65536
3              serialized      13792273858822144        65536
4              serialized      4718592                  65536
5              serialized      4294967296               65536
6              serialized      4503608217305088         65536
7              serialized      14073748835532800        65536

big numbers seems unrelated. Did you updated commit-msg after fixing s/* 8 * 
8/* 8/ bug of v10?


Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
  tests/qemu-iotests/qcow2_format.py | 41 ++++++++++++++++++++++++++++++++++++++
  1 file changed, 41 insertions(+)

diff --git a/tests/qemu-iotests/qcow2_format.py 
b/tests/qemu-iotests/qcow2_format.py
index ca0d350..ad1918c 100644
--- a/tests/qemu-iotests/qcow2_format.py
+++ b/tests/qemu-iotests/qcow2_format.py
@@ -175,6 +175,10 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
          entry_raw_size = self.bitmap_dir_entry_raw_size()
          padding = ((entry_raw_size + 7) & ~7) - entry_raw_size
          fd.seek(padding, 1)
+        self.bitmap_table = Qcow2BitmapTable(fd=fd,
+                                             offset=self.bitmap_table_offset,
+                                             size=self.bitmap_table_size,
+                                             cluster_size=self.cluster_size)
def bitmap_dir_entry_raw_size(self):
          return struct.calcsize(self.fmt) + self.name_size + \
@@ -183,6 +187,43 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
      def dump(self):
          print(f'{"Bitmap name":<25} {self.name}')
          super(Qcow2BitmapDirEntry, self).dump()
+        self.bitmap_table.dump()
+
+
+class Qcow2BitmapTableEntry:

Why not to derive it from Qcow2Struct? It will have only one field, but it will 
work, and we don't need to open-code loading in Qcow2BitmapTable

+
+    BME_TABLE_ENTRY_OFFSET_MASK = 0x00fffffffffffe00
+    BME_TABLE_ENTRY_FLAG_ALL_ONES = 1
+
+    def __init__(self, entry):
+        self.offset = entry & self.BME_TABLE_ENTRY_OFFSET_MASK
+        if self.offset:
+            self.type = 'serialized'
+        elif entry & self.BME_TABLE_ENTRY_FLAG_ALL_ONES:
+            self.type = 'all-ones'
+        else:
+            self.type = 'all-zeroes'

Would be good to note if reserved bits are set, as well as wrong combination of 
offset and all-ones bit.

+
+
+class Qcow2BitmapTable:
+
+    def __init__(self, fd, offset, size, cluster_size):
+        self.entries = []
+        self.cluster_size = cluster_size
+        table_size = size * 8

you may rename size to nb_entries, to make it obvious what "size" is (I know, that it's 
my idea to call it "size" in qcow2 spec. Probably bad one).

+        position = fd.tell()
+        fd.seek(offset)
+        table = [e[0] for e in struct.iter_unpack('>Q', fd.read(table_size))]

this should be self.entries = [Qcow2BitmapTableEntry(fd) for _ in 
range(nb_entries)]

+        fd.seek(position)
+        for entry in table:
+            self.entries.append(Qcow2BitmapTableEntry(entry))
+
+    def dump(self):
+        size = self.cluster_size
+        bitmap_table = enumerate(self.entries)
+        print(f'{"Bitmap table":<14} {"type":<15} {"offset":<24} {"size"}')
+        for i, entry in bitmap_table:
+            print(f'{i:<14} {entry.type:<15} {entry.offset:<24} {size}')
QCOW2_EXT_MAGIC_BITMAPS = 0x23852875



--
Best regards,
Vladimir



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