^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ======================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) Enhanced Read-Only File System - EROFS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) ======================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) Overview
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) EROFS file-system stands for Enhanced Read-Only File System. Different
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) from other read-only file systems, it aims to be designed for flexibility,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) scalability, but be kept simple and high performance.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) It is designed as a better filesystem solution for the following scenarios:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) - read-only storage media or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) - part of a fully trusted read-only solution, which means it needs to be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) immutable and bit-for-bit identical to the official golden image for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) their releases due to security and other considerations and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) - hope to save some extra storage space with guaranteed end-to-end performance
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) by using reduced metadata and transparent file compression, especially
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) for those embedded devices with limited memory (ex, smartphone);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) Here is the main features of EROFS:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) - Little endian on-disk design;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) - Currently 4KB block size (nobh) and therefore maximum 16TB address space;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) - Metadata & data could be mixed by design;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) - 2 inode versions for different requirements:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) ===================== ============ =====================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) compact (v1) extended (v2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) ===================== ============ =====================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) Inode metadata size 32 bytes 64 bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) Max file size 4 GB 16 EB (also limited by max. vol size)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) Max uids/gids 65536 4294967296
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) File change time no yes (64 + 32-bit timestamp)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) Max hardlinks 65536 4294967296
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) Metadata reserved 4 bytes 14 bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) ===================== ============ =====================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) - Support extended attributes (xattrs) as an option;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) - Support xattr inline and tail-end data inline for all files;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) - Support POSIX.1e ACLs by using xattrs;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) - Support transparent file compression as an option:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) LZ4 algorithm with 4 KB fixed-sized output compression for high performance.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) The following git tree provides the file system user-space tools under
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) development (ex, formatting tool mkfs.erofs):
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) - git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) Bugs and patches are welcome, please kindly help us and send to the following
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) linux-erofs mailing list:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) - linux-erofs mailing list <linux-erofs@lists.ozlabs.org>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) Mount options
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) =============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) =================== =========================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) (no)user_xattr Setup Extended User Attributes. Note: xattr is enabled
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) by default if CONFIG_EROFS_FS_XATTR is selected.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) (no)acl Setup POSIX Access Control List. Note: acl is enabled
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) by default if CONFIG_EROFS_FS_POSIX_ACL is selected.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) cache_strategy=%s Select a strategy for cached decompression from now on:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) ========== =============================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) disabled In-place I/O decompression only;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) readahead Cache the last incomplete compressed physical
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) cluster for further reading. It still does
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) in-place I/O decompression for the rest
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) compressed physical clusters;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) readaround Cache the both ends of incomplete compressed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) physical clusters for further reading.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) It still does in-place I/O decompression
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) for the rest compressed physical clusters.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) ========== =============================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) dax={always,never} Use direct access (no page cache). See
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) Documentation/filesystems/dax.rst.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) dax A legacy option which is an alias for ``dax=always``.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) =================== =========================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) On-disk details
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) ===============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) Summary
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) -------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) Different from other read-only file systems, an EROFS volume is designed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) to be as simple as possible::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) |-> aligned with the block size
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) ____________________________________________________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) | |SB| | ... | Metadata | ... | Data | Metadata | ... | Data |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) |_|__|_|_____|__________|_____|______|__________|_____|______|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) 0 +1K
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) All data areas should be aligned with the block size, but metadata areas
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) may not. All metadatas can be now observed in two different spaces (views):
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) 1. Inode metadata space
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) Each valid inode should be aligned with an inode slot, which is a fixed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) value (32 bytes) and designed to be kept in line with compact inode size.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) Each inode can be directly found with the following formula:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) inode offset = meta_blkaddr * block_size + 32 * nid
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) |-> aligned with 8B
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) |-> followed closely
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) + meta_blkaddr blocks |-> another slot
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) _____________________________________________________________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) | ... | inode | xattrs | extents | data inline | ... | inode ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) |________|_______|(optional)|(optional)|__(optional)_|_____|__________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) |-> aligned with the inode slot size
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) .____________________________________________________|-> aligned with 4B
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) | xattr_ibody_header | shared xattrs | inline xattrs |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) |____________________|_______________|_______________|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) |-> 12 bytes <-|->x * 4 bytes<-| .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) ._______________________________.______________________.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) | id | id | id | id | ... | id | ent | ... | ent| ... |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) |____|____|____|____|______|____|_____|_____|____|_____|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) |-> aligned with 4B
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) |-> aligned with 4B
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) Inode could be 32 or 64 bytes, which can be distinguished from a common
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) field which all inode versions have -- i_format::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) __________________ __________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) | i_format | | i_format |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) |__________________| |__________________|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) | ... | | ... |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) | | | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) |__________________| 32 bytes | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) | |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) |__________________| 64 bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) Xattrs, extents, data inline are followed by the corresponding inode with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) proper alignment, and they could be optional for different data mappings.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) _currently_ total 4 valid data mappings are supported:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) == ====================================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) 0 flat file data without data inline (no extent);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) 1 fixed-sized output data compression (with non-compacted indexes);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) 2 flat file data with tail packing data inline (no extent);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) 3 fixed-sized output data compression (with compacted indexes, v5.3+).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) == ====================================================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) The size of the optional xattrs is indicated by i_xattr_count in inode
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) header. Large xattrs or xattrs shared by many different files can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) stored in shared xattrs metadata rather than inlined right after inode.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) 2. Shared xattrs metadata space
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) Shared xattrs space is similar to the above inode space, started with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) a specific block indicated by xattr_blkaddr, organized one by one with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) proper align.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) Each share xattr can also be directly found by the following formula:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) xattr offset = xattr_blkaddr * block_size + 4 * xattr_id
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) |-> aligned by 4 bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) + xattr_blkaddr blocks |-> aligned with 4 bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) _________________________________________________________________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) | ... | xattr_entry | xattr data | ... | xattr_entry | xattr data ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) |________|_____________|_____________|_____|______________|_______________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) Directories
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) -----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) All directories are now organized in a compact on-disk format. Note that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) each directory block is divided into index and name areas in order to support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) random file lookup, and all directory entries are _strictly_ recorded in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) alphabetical order in order to support improved prefix binary search
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) algorithm (could refer to the related source code).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) ___________________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) / |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) / ______________|________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) / / | nameoff1 | nameoffN-1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) ____________.______________._______________v________________v__________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) | dirent | dirent | ... | dirent | filename | filename | ... | filename |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) |___.0___|____1___|_____|___N-1__|____0_____|____1_____|_____|___N-1____|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) \ ^
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) \ | * could have
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) \ | trailing '\0'
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) \________________________| nameoff0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) Directory block
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) Note that apart from the offset of the first filename, nameoff0 also indicates
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) the total number of directory entries in this block since it is no need to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) introduce another on-disk field at all.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) Compression
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) -----------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) Currently, EROFS supports 4KB fixed-sized output transparent file compression,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) as illustrated below::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) |---- Variant-Length Extent ----|-------- VLE --------|----- VLE -----
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) clusterofs clusterofs clusterofs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) | | | logical data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225) _________v_______________________________v_____________________v_______________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) ... | . | | . | | . | ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) ____|____.________|_____________|________.____|_____________|__.__________|____
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228) |-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229) size size size size size
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) . . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) . . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) . . . .
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) _______._____________._____________._____________._____________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) ... | | | | ... physical data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) _______|_____________|_____________|_____________|_____________________
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) |-> cluster <-|-> cluster <-|-> cluster <-|
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237) size size size
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) Currently each on-disk physical cluster can contain 4KB (un)compressed data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) at most. For each logical cluster, there is a corresponding on-disk index to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241) describe its cluster type, physical cluster address, etc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243) See "struct z_erofs_vle_decompressed_index" in erofs_fs.h for more details.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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