xref: /linux/fs/erofs/Kconfig (revision 67f8bc848ee31831336bd478e57d2f993551902e)

# SPDX-License-Identifier: GPL-2.0-only

config EROFS_FS
	tristate "EROFS filesystem support"
	depends on BLOCK
	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 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.

	  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_LZMA_DEFAULT_MAX_STREAMS
	int "EROFS LZMA default maximum decompression streams" if SMP
	depends on EROFS_FS_ZIP_LZMA
	range 1 NR_CPUS if SMP
	range 1 1 if !SMP
	default 16 if SMP && NR_CPUS >= 16
	default NR_CPUS if SMP
	default 1
	help
	  By default EROFS allocates one LZMA decompression stream per CPU.
	  Each stream can hold a dictionary of up to 8 MiB taken from the
	  mounted image, so on systems with many CPUs this can reserve a lot
	  of memory.  This caps the default; the lzma_streams module parameter
	  still overrides it.

	  If unsure, keep the suggested default (16 or lower).

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_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
	select FS_STACK
	help
	  This enables page cache sharing among inodes with identical
	  content fingerprints on the same machine.

	  If unsure, say N.