# 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 lightweight read-only
file system with modern designs (e.g. no buffer heads, inline
xattrs/data, chunk-based deduplication, multiple devices, etc.) for
scenarios which need high-performance read-only solutions, e.g.
smartphones with Android OS, LiveCDs
and high-density hosts with
numerous containers
;
It also provides transparent compression
and deduplication support to
improve storage density
and maintain relatively high compression
ratios,
and it implements in-place decompression to temporarily reuse
page cache for compressed data using proper strategies, which is
quite useful for ensuring guaranteed end-to-end runtime decompression
performance under extreme memory pressure without extra cost.
See the documentation at <file:Documentation/filesystems/erofs.rst>
and the web pages at <
https://erofs.docs.kernel.org> for more details.
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 transparent compression support for EROFS file systems.
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
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.
If unsure, say N.
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.
DEFLATE support is an experimental feature for now
and so most
file systems will be readable without selecting this option.
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.
Zstandard support is an experimental feature for now
and so most
file systems will be readable without selecting this option.
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.
