Hi, This is actually the 2nd patchset of erofs file system, the original patchset can be found at Link: https://marc.info/?l=linux-fsdevel&m=152776480425624 In order to keep up with the mainline linux-kernel changes and improve it in a more active and timely manner, we put forword this upstream proposal for linux-staging. EROFS file system is a read-only file system with compression support designed for certain devices (especially embeded devices) with very limited physical memory and lots of memory consumers, such as Android devices. It aimes to provide a complete compression solution for such devices focuing on high performance and little extra memory overhead. It is perferred to select larger compressed cluster sizes (generally >= 128k) for traditional compression file systems. It reads and decompresses a large compressed cluster at once, which has a good-looking random read number when memory is sufficient because all historial decompressed data is expected to be cached in memory. However, it also induces destructive effects when such devices have no enough spare memory for caching and decompression. EROFS file system acts in some different way. It uses fixed-sized compressed size rather than fixed-sized input size, namely VLE (variable-length extent) compression, which has at least three adventages: 1) all data read from block device at once can be utilized, and read amplification can be easier to estimate and control; 2) generally, it has a better compression ratio than fixed-sized input compression approaches configured with the same size; 3) aggressively optimized paths such as partial page read can be implemented to gain better performance for page-unaligned read (unimplemented yet, in TODO list). As can be seen, VLE compression does a great job in small compressed cluster sizes, which is of course suitable for devices with limited memory. In this patchset, an in-place decompresion is also introduced to minimize extra memory usage. Apart from compression, EROFS also has the following features available and some limits: o page-sized block support (currently, and no buffer-head); o 32-bit block address (16TB for 4KB block); o selectable v1 (32 bytes) / v2 (64 bytes) inode; o 32-bit / 64-bit file size; o 64-bit node number for addressing inodes; o 64-bit s and 32-bit ns timestamps; o inline data support; o inline and shared xattr support; o metadata and data can be mixed (optional); o special inode support; o posix acl support. The file system is still actively WIP, see _TODO_ for more details. Any comments are welcome. :) Change log from the original patchset ===================================== o Introduce a new erofs decompression subsystem, which has better sequencial read than the original patchset, and its random read remains almost the same (note that erofs still only fully support page-sized compressed cluster as the compression unit, however some additional code enabling larger compressed clustersizes is also added in this version); o Avoid LINUX_VERSION macros for linux-staging upstream o several bugfix and cleanup Short log ========= Chao Yu (3): staging: erofs: support special inode staging: erofs: introduce error injection infrastructure staging: erofs: support tracepoint Gao Xiang (22): staging: erofs: add on-disk layout staging: erofs: add erofs in-memory stuffs staging: erofs: add super block operations staging: erofs: add raw address_space operations staging: erofs: add inode operations staging: erofs: add directory operations staging: erofs: add namei functions staging: erofs: update Kconfig and Makefile staging: erofs: introduce xattr & acl support staging: erofs: <linux/tagptr.h>: introduce tagged pointer staging: erofs: introduce pagevec for unzip subsystem staging: erofs: add erofs_map_blocks_iter staging: erofs: add erofs_allocpage staging: erofs: globalize prepare_bio and __submit_bio staging: erofs: introduce a customized LZ4 decompression staging: erofs: add a generic z_erofs VLE decompressor staging: erofs: introduce superblock registration staging: erofs: introduce erofs shrinker staging: erofs: introduce workstation for decompression staging: erofs: introduce VLE decompression support staging: erofs: introduce cached decompression staging: erofs: add a TODO and update MAINTAINERS for staging MAINTAINERS | 7 + drivers/staging/Kconfig | 2 + drivers/staging/Makefile | 1 + drivers/staging/erofs/Kconfig | 141 ++ drivers/staging/erofs/Makefile | 13 + drivers/staging/erofs/TODO | 45 + drivers/staging/erofs/data.c | 385 +++++ drivers/staging/erofs/dir.c | 145 ++ drivers/staging/erofs/erofs_fs.h | 266 ++++ drivers/staging/erofs/include/linux/tagptr.h | 110 ++ drivers/staging/erofs/include/trace/events/erofs.h | 240 +++ drivers/staging/erofs/inode.c | 283 ++++ drivers/staging/erofs/internal.h | 556 +++++++ drivers/staging/erofs/lz4defs.h | 227 +++ drivers/staging/erofs/namei.c | 251 +++ drivers/staging/erofs/super.c | 649 ++++++++ drivers/staging/erofs/unzip_lz4.c | 251 +++ drivers/staging/erofs/unzip_pagevec.h | 172 +++ drivers/staging/erofs/unzip_vle.c | 1634 ++++++++++++++++++++ drivers/staging/erofs/unzip_vle.h | 239 +++ drivers/staging/erofs/unzip_vle_lz4.c | 209 +++ drivers/staging/erofs/utils.c | 270 ++++ drivers/staging/erofs/xattr.c | 579 +++++++ drivers/staging/erofs/xattr.h | 93 ++ 24 files changed, 6768 insertions(+) create mode 100644 drivers/staging/erofs/Kconfig create mode 100644 drivers/staging/erofs/Makefile create mode 100644 drivers/staging/erofs/TODO create mode 100644 drivers/staging/erofs/data.c create mode 100644 drivers/staging/erofs/dir.c create mode 100644 drivers/staging/erofs/erofs_fs.h create mode 100644 drivers/staging/erofs/include/linux/tagptr.h create mode 100644 drivers/staging/erofs/include/trace/events/erofs.h create mode 100644 drivers/staging/erofs/inode.c create mode 100644 drivers/staging/erofs/internal.h create mode 100644 drivers/staging/erofs/lz4defs.h create mode 100644 drivers/staging/erofs/namei.c create mode 100644 drivers/staging/erofs/super.c create mode 100644 drivers/staging/erofs/unzip_lz4.c create mode 100644 drivers/staging/erofs/unzip_pagevec.h create mode 100644 drivers/staging/erofs/unzip_vle.c create mode 100644 drivers/staging/erofs/unzip_vle.h create mode 100644 drivers/staging/erofs/unzip_vle_lz4.c create mode 100644 drivers/staging/erofs/utils.c create mode 100644 drivers/staging/erofs/xattr.c create mode 100644 drivers/staging/erofs/xattr.h Thanks, Gao Xiang -- 1.9.1
