Documentation/filesystems/ext4/ondisk/blockmap.rst


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.. SPDX-License-Identifier: GPL-2.0

+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| i.i\_block Offset   | Where It Points                                                                                                                                                                                                              |
+=====================+==============================================================================================================================================================================================================================+
| 0 to 11             | Direct map to file blocks 0 to 11.                                                                                                                                                                                           |
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 12                  | Indirect block: (file blocks 12 to (``$block_size`` / 4) + 11, or 12 to 1035 if 4KiB blocks)                                                                                                                                 |
|                     |                                                                                                                                                                                                                              |
|                     | +------------------------------+--------------------------------------------------------------------+                                                                                                                        |
|                     | | Indirect Block Offset        | Where It Points                                                    |                                                                                                                        |
|                     | +==============================+====================================================================+                                                                                                                        |
|                     | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |                                                                                                                        |
|                     | +------------------------------+--------------------------------------------------------------------+                                                                                                                        |
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 13                  | Double-indirect block: (file blocks ``$block_size``/4 + 12 to (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 11, or 1036 to 1049611 if 4KiB blocks)                                                                     |
|                     |                                                                                                                                                                                                                              |
|                     | +--------------------------------+---------------------------------------------------------------------------------------------------------+                                                                                 |
|                     | | Double Indirect Block Offset   | Where It Points                                                                                         |                                                                                 |
|                     | +================================+=========================================================================================================+                                                                                 |
|                     | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks)                                      |                                                                                 |
|                     | |                                |                                                                                                         |                                                                                 |
|                     | |                                | +------------------------------+--------------------------------------------------------------------+   |                                                                                 |
|                     | |                                | | Indirect Block Offset        | Where It Points                                                    |   |                                                                                 |
|                     | |                                | +==============================+====================================================================+   |                                                                                 |
|                     | |                                | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |   |                                                                                 |
|                     | |                                | +------------------------------+--------------------------------------------------------------------+   |                                                                                 |
|                     | +--------------------------------+---------------------------------------------------------------------------------------------------------+                                                                                 |
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 14                  | Triple-indirect block: (file blocks (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12 to (``$block_size`` / 4) ^ 3 + (``$block_size`` / 4) ^ 2 + (``$block_size`` / 4) + 12, or 1049612 to 1074791436 if 4KiB blocks)   |
|                     |                                                                                                                                                                                                                              |
|                     | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+                                          |
|                     | | Triple Indirect Block Offset   | Where It Points                                                                                                                                |                                          |
|                     | +================================+================================================================================================================================================+                                          |
|                     | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) double indirect blocks (1024 if 4KiB blocks)                                                                      |                                          |
|                     | |                                |                                                                                                                                                |                                          |
|                     | |                                | +--------------------------------+---------------------------------------------------------------------------------------------------------+   |                                          |
|                     | |                                | | Double Indirect Block Offset   | Where It Points                                                                                         |   |                                          |
|                     | |                                | +================================+=========================================================================================================+   |                                          |
|                     | |                                | | 0 to (``$block_size`` / 4)     | Map to (``$block_size`` / 4) indirect blocks (1024 if 4KiB blocks)                                      |   |                                          |
|                     | |                                | |                                |                                                                                                         |   |                                          |
|                     | |                                | |                                | +------------------------------+--------------------------------------------------------------------+   |   |                                          |
|                     | |                                | |                                | | Indirect Block Offset        | Where It Points                                                    |   |   |                                          |
|                     | |                                | |                                | +==============================+====================================================================+   |   |                                          |
|                     | |                                | |                                | | 0 to (``$block_size`` / 4)   | Direct map to (``$block_size`` / 4) blocks (1024 if 4KiB blocks)   |   |   |                                          |
|                     | |                                | |                                | +------------------------------+--------------------------------------------------------------------+   |   |                                          |
|                     | |                                | +--------------------------------+---------------------------------------------------------------------------------------------------------+   |                                          |
|                     | +--------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+                                          |
+---------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+