# SPDX-License-Identifier: GPL-2.0-only config EROFS_FS tristate "EROFS filesystem support" depends on BLOCK select CACHEFILES if EROFS_FS_ONDEMAND select CRC32 select CRYPTO if EROFS_FS_ZIP_ACCEL select CRYPTO_DEFLATE if EROFS_FS_ZIP_ACCEL select FS_IOMAP select LZ4_DECOMPRESS if EROFS_FS_ZIP select NETFS_SUPPORT if EROFS_FS_ONDEMAND select XXHASH if EROFS_FS_XATTR select XZ_DEC if EROFS_FS_ZIP_LZMA select XZ_DEC_MICROLZMA if EROFS_FS_ZIP_LZMA select ZLIB_INFLATE if EROFS_FS_ZIP_DEFLATE select ZSTD_DECOMPRESS if EROFS_FS_ZIP_ZSTD help EROFS (Enhanced Read-Only File System) is a modern, lightweight, secure read-only filesystem for various use cases, such as immutable system images, container images, application sandboxes, and datasets. EROFS uses a flexible, hierarchical on-disk design so that features can be enabled on demand: the core on-disk format is block-aligned in order to perform optimally on all kinds of devices, including block and memory-backed devices; the format is easy to parse and has zero metadata redundancy, unlike generic filesystems, making it ideal for filesystem auditing and remote access; inline data, random-access friendly directory data, inline/shared extended attributes and chunk-based deduplication ensure space efficiency while maintaining high performance. Optionally, it supports multiple devices to reference external data, enabling data sharing for container images. It also has advanced encoded on-disk layouts, particularly for data compression and fine-grained deduplication. It utilizes fixed-size output compression to improve storage density while keeping relatively high compression ratios. Furthermore, it implements in-place decompression to reuse file pages to keep compressed data temporarily with proper strategies, which ensures guaranteed end-to-end runtime performance under extreme memory pressure without extra cost. For more details, see the web pages at <https://erofs.docs.kernel.org> and the documentation at <file:Documentation/filesystems/erofs.rst>. To compile EROFS filesystem support as a module, choose M here. The module will be called erofs. If unsure, say N. config EROFS_FS_DEBUG bool "EROFS debugging feature" depends on EROFS_FS help Print debugging messages and enable more BUG_ONs which check filesystem consistency and find potential issues aggressively, which can be used for Android eng build, for example. For daily use, say N. config EROFS_FS_XATTR bool "EROFS extended attributes" depends on EROFS_FS default y help Extended attributes are name:value pairs associated with inodes by the kernel or by users (see the attr(5) manual page, or visit <http://acl.bestbits.at/> for details). If unsure, say N. config EROFS_FS_POSIX_ACL bool "EROFS Access Control Lists" depends on EROFS_FS_XATTR select FS_POSIX_ACL default y help Posix Access Control Lists (ACLs) support permissions for users and groups beyond the owner/group/world scheme. To learn more about Access Control Lists, visit the POSIX ACLs for Linux website <http://acl.bestbits.at/>. If you don't know what Access Control Lists are, say N. config EROFS_FS_SECURITY bool "EROFS Security Labels" depends on EROFS_FS_XATTR default y help Security labels provide an access control facility to support Linux Security Models (LSMs) accepted by AppArmor, SELinux, Smack and TOMOYO Linux. This option enables an extended attribute handler for file security labels in the erofs filesystem, so that it requires enabling the extended attribute support in advance. If you are not using a security module, say N. config EROFS_FS_BACKED_BY_FILE bool "File-backed EROFS filesystem support" depends on EROFS_FS default y help This allows EROFS to use filesystem image files directly, without the intercession of loopback block devices or likewise. It is particularly useful for container images with numerous blobs and other sandboxes, where loop devices behave intricately. It can also be used to simplify error-prone lifetime management of unnecessary virtual block devices. Note that this feature, along with ongoing fanotify pre-content hooks, will eventually replace "EROFS over fscache." If you don't want to enable this feature, say N. config EROFS_FS_ZIP bool "EROFS Data Compression Support" depends on EROFS_FS default y help Enable EROFS compression layouts so that filesystems containing compressed files can be parsed by the kernel. If you don't want to enable compression feature, say N. config EROFS_FS_ZIP_LZMA bool "EROFS LZMA compressed data support" depends on EROFS_FS_ZIP default y help Saying Y here includes support for reading EROFS file systems containing LZMA compressed data, specifically called microLZMA. It gives better compression ratios than the default LZ4 format, at the expense of more CPU overhead. Say N if you want to disable LZMA compression support. config EROFS_FS_ZIP_DEFLATE bool "EROFS DEFLATE compressed data support" depends on EROFS_FS_ZIP help Saying Y here includes support for reading EROFS file systems containing DEFLATE compressed data. It gives better compression ratios than the default LZ4 format, while it costs more CPU overhead. If unsure, say N. config EROFS_FS_ZIP_ZSTD bool "EROFS Zstandard compressed data support" depends on EROFS_FS_ZIP help Saying Y here includes support for reading EROFS file systems containing Zstandard compressed data. It gives better compression ratios than the default LZ4 format, while it costs more CPU overhead and memory footprint. If unsure, say N. config EROFS_FS_ZIP_ACCEL bool "EROFS hardware decompression support" depends on EROFS_FS_ZIP help Saying Y here includes hardware accelerator support for reading EROFS file systems containing compressed data. It gives better decompression speed than the software-implemented decompression, and it costs lower CPU overhead. Hardware accelerator support is an experimental feature for now and file systems are still readable without selecting this option. If unsure, say N. config EROFS_FS_ONDEMAND bool "EROFS fscache-based on-demand read support (deprecated)" depends on EROFS_FS select FSCACHE select CACHEFILES_ONDEMAND help This permits EROFS to use fscache-backed data blobs with on-demand read support. It is now deprecated and scheduled to be removed from the kernel after fanotify pre-content hooks are landed. If unsure, say N. config EROFS_FS_PCPU_KTHREAD bool "EROFS per-cpu decompression kthread workers" depends on EROFS_FS_ZIP help Saying Y here enables per-CPU kthread workers pool to carry out async decompression for low latencies on some architectures. If unsure, say N. config EROFS_FS_PCPU_KTHREAD_HIPRI bool "EROFS high priority per-CPU kthread workers" depends on EROFS_FS_ZIP && EROFS_FS_PCPU_KTHREAD default y help This permits EROFS to configure per-CPU kthread workers to run at higher priority. If unsure, say N. config EROFS_FS_PAGE_CACHE_SHARE bool "EROFS page cache share support (experimental)" depends on EROFS_FS && EROFS_FS_XATTR && !EROFS_FS_ONDEMAND help This enables page cache sharing among inodes with identical content fingerprints on the same machine. If unsure, say N.
