xref: /linux/Documentation/filesystems/ext4/blockmap.rst (revision 95298d63c67673c654c08952672d016212b26054)
1.. SPDX-License-Identifier: GPL-2.0
2
3+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
4| i.i\_block Offset   | Where It Points                                                                                                                                                                                                              |
5+=====================+==============================================================================================================================================================================================================================+
6| 0 to 11             | Direct map to file blocks 0 to 11.                                                                                                                                                                                           |
7+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
8| 12                  | Indirect block: (file blocks 12 to (``$block_size`` / 4) + 11, or 12 to 1035 if 4KiB blocks)                                                                                                                                 |
9|                     |                                                                                                                                                                                                                              |
10|                     | +------------------------------+--------------------------------------------------------------------+                                                                                                                        |
11|                     | | Indirect Block Offset        | Where It Points                                                    |                                                                                                                        |
12|                     | +==============================+====================================================================+                                                                                                                        |
13|                     | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |                                                                                                                        |
14|                     | +------------------------------+--------------------------------------------------------------------+                                                                                                                        |
15+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
16| 13                  | Double-indirect block: (file blocks ``$block_size``/4 + 12 to (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 11, or 1036 to 1049611 if 4KiB blocks)                                                                     |
17|                     |                                                                                                                                                                                                                              |
18|                     | +--------------------------------+---------------------------------------------------------------------------------------------------------+                                                                                 |
19|                     | | Double Indirect Block Offset   | Where It Points                                                                                         |                                                                                 |
20|                     | +================================+=========================================================================================================+                                                                                 |
21|                     | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks)                                      |                                                                                 |
22|                     | |                                |                                                                                                         |                                                                                 |
23|                     | |                                | +------------------------------+--------------------------------------------------------------------+   |                                                                                 |
24|                     | |                                | | Indirect Block Offset        | Where It Points                                                    |   |                                                                                 |
25|                     | |                                | +==============================+====================================================================+   |                                                                                 |
26|                     | |                                | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |   |                                                                                 |
27|                     | |                                | +------------------------------+--------------------------------------------------------------------+   |                                                                                 |
28|                     | +--------------------------------+---------------------------------------------------------------------------------------------------------+                                                                                 |
29+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
30| 14                  | Triple-indirect block: (file blocks (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12 to (``$block_size`` / 4) ^ 3 + (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12, or 1049612 to 1074791436 if 4KiB blocks)   |
31|                     |                                                                                                                                                                                                                              |
32|                     | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+                                          |
33|                     | | Triple Indirect Block Offset   | Where It Points                                                                                                                                |                                          |
34|                     | +================================+================================================================================================================================================+                                          |
35|                     | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) double indirect blocks (1024 if 4KiB blocks)                                                                      |                                          |
36|                     | |                                |                                                                                                                                                |                                          |
37|                     | |                                | +--------------------------------+---------------------------------------------------------------------------------------------------------+   |                                          |
38|                     | |                                | | Double Indirect Block Offset   | Where It Points                                                                                         |   |                                          |
39|                     | |                                | +================================+=========================================================================================================+   |                                          |
40|                     | |                                | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks)                                      |   |                                          |
41|                     | |                                | |                                |                                                                                                         |   |                                          |
42|                     | |                                | |                                | +------------------------------+--------------------------------------------------------------------+   |   |                                          |
43|                     | |                                | |                                | | Indirect Block Offset        | Where It Points                                                    |   |   |                                          |
44|                     | |                                | |                                | +==============================+====================================================================+   |   |                                          |
45|                     | |                                | |                                | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |   |   |                                          |
46|                     | |                                | |                                | +------------------------------+--------------------------------------------------------------------+   |   |                                          |
47|                     | |                                | +--------------------------------+---------------------------------------------------------------------------------------------------------+   |                                          |
48|                     | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+                                          |
49+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
50