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Subject: Re: [PATCH v8 00/24] erofs: promote erofs from staging v8
To:     Gao Xiang <gaoxiang25@huawei.com>, <linux-fsdevel@vger.kernel.org>,
        <devel@driverdev.osuosl.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>
CC:     LKML <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Theodore Ts'o <tytso@mit.edu>, "Pavel Machek" <pavel@denx.de>,
        David Sterba <dsterba@suse.cz>,
        Amir Goldstein <amir73il@gmail.com>,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J . Wong" <darrick.wong@oracle.com>,
        Dave Chinner <david@fromorbit.com>,
        "Jaegeuk Kim" <jaegeuk@kernel.org>, Jan Kara <jack@suse.cz>,
        Richard Weinberger <richard@nod.at>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        <linux-erofs@lists.ozlabs.org>, Miao Xie <miaoxie@huawei.com>,
        Li Guifu <bluce.liguifu@huawei.com>,
        Fang Wei <fangwei1@huawei.com>
References: <20190815044155.88483-1-gaoxiang25@huawei.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <9ba5968d-45a6-c66e-52df-ae232cc42365@huawei.com>
Date:   Fri, 30 Aug 2019 15:48:26 +0800
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On 2019/8/15 12:41, Gao Xiang wrote:
> [I strip the previous cover letter, the old one can be found in v6:
>  https://lore.kernel.org/r/20190802125347.166018-1-gaoxiang25@huawei.com/]
> 
> We'd like to submit a formal moving patch applied to staging tree
> for 5.4, before that we'd like to hear if there are some ACKs,
> suggestions or NAKs, objections of EROFS. Therefore, we can improve
> it in this round or rethink about the whole thing.
> 
> As related materials mentioned [1] [2], the goal of EROFS is to
> save extra storage space with guaranteed end-to-end performance
> for read-only files, which has better performance over exist Linux
> compression filesystems based on fixed-sized output compression
> and inplace decompression. It even has better performance in
> a large compression ratio range compared with generic uncompressed
> filesystems with proper CPU-storage combinations. And we think this
> direction is correct and a dedicated kernel team is continuously /
> actively working on improving it, enough testers and beta / end
> users using it.
> 
> EROFS has been applied to almost all in-service HUAWEI smartphones
> (Yes, the number is still increasing by time) and it seems like
> a success. It can be used in more wider scenarios. We think it's
> useful for Linux / Android OS community and it's the time moving
> out of staging.
> 
> In order to get started, latest stable mkfs.erofs is available at
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git -b dev
> 
> with README in the repository.
> 
> We are still tuning sequential read performance for ultra-fast
> speed NVME SSDs like Samsung 970PRO, but at least now you can
> try on your PC with some data with proper compression ratio,
> the latest Linux kernel, USB stick for convenience sake and
> a not very old-fashioned CPU. There are also benchmarks available
> in the above materials mentioned.
> 
> EROFS is a self-contained filesystem driver. Although there are
> still some TODOs to be more generic, we will actively keep on
> developping / tuning EROFS with the evolution of Linux kernel
> as the other in-kernel filesystems.
> 
> As I mentioned before in LSF/MM 2019, in the future, we'd like
> to generalize the decompression engine into a library for other
> fses to use after the whole system is mature like fscrypt.
> However, such metadata should be designed respectively for
> each fs, and synchronous metadata read cost will be larger
> than EROFS because of those ondisk limitation. Therefore EROFS
> is still a better choice for read-only scenarios.
> 
> EROFS is now ready for reviewing and moving, and the code is
> already cleaned up as shiny floors... Please kindly take some
> precious time, share your comments about EROFS and let us know
> your opinion about this. It's really important for us since
> generally speaking, we like to use Linux _in-tree_ stuffs rather
> than lack of supported out-of-tree / orphan stuffs as well.

EROFS proposes its very unique fixed-sized output compression and inplace
decompression framework joining into the ecosystem of compression filesystem, I
think it will enrich diversity of compression filesystem, and bring healthy
competition there.

I do believe this is the right time to promote erofs to fs/ directory, let it be
the formal member of filesystem clubhouse.

Acked-by: Chao Yu <yuchao0@huawei.com>

Thanks

> 
> Thank you in advance,
> Gao Xiang
> 
> [1] https://kccncosschn19eng.sched.com/event/Nru2/erofs-an-introduction-and-our-smartphone-practice-xiang-gao-huawei
> [2] https://www.usenix.org/conference/atc19/presentation/gao
> 
> Changelog from v7:
>  o keep up with the latest staging tree in addition to
>    the latest staging patch:
>    https://lore.kernel.org/r/20190814103705.60698-1-gaoxiang25@huawei.com/
>    - use EUCLEAN for fs corruption cases suggested by Pavel;
>    - turn EIO into EOPNOTSUPP for unsupported on-disk format;
>    - fix all misused ENOTSUPP into EOPNOTSUPP pointed out by Chao;
>  o update cover letter
> 
> It can also be found in git at tag "erofs_2019-08-15" (will be shown later) at:
>  https://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git/
> 
> and the latest fs code is available at:
>  https://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git/tree/fs/erofs?h=erofs-outofstaging
> 
> Changelog from v6:
>  o keep up with the latest staging patchset
>    https://lore.kernel.org/linux-fsdevel/20190813023054.73126-1-gaoxiang25@huawei.com/
>    in order to fix the following cases:
>    - inline erofs_inode_is_data_compressed() in erofs_fs.h;
>    - remove incomplete cleancache;
>    - remove all BUG_ON in EROFS.
>  o Removing the file names from the comments at the top of the files
>    suggested by Stephen will be applied to the real moving patch later.
> 
> Changelog from v5:
>  o keep up with "[PATCH v2] staging: erofs: updates according to erofs-outofstaging v4"
>     https://lore.kernel.org/lkml/20190731155752.210602-1-gaoxiang25@huawei.com/
>    which mainly addresses review comments from Chao:
>   - keep the marco EROFS_IO_MAX_RETRIES_NOFAIL in internal.h;
>   - kill a redundant NULL check in "__stagingpage_alloc";
>   - add some descriptions in document about "use_vmap";
>   - rearrange erofs_vmap of "staging: erofs: kill CONFIG_EROFS_FS_USE_VM_MAP_RAM";
> 
>  o all changes have been merged into staging tree, which are under staging-testing:
>     https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git/log/?h=staging-testing
> 
> Changelog from v4:
>  o rebase on Linux 5.3-rc1;
> 
>  o keep up with "staging: erofs: updates according to erofs-outofstaging v4"
>    in order to get main code bit-for-bit identical with staging tree:
>     https://lore.kernel.org/lkml/20190729065159.62378-1-gaoxiang25@huawei.com/
> 
> Changelog from v3:
>  o use GPL-2.0-only for SPDX-License-Identifier suggested by Stephen;
> 
>  o kill all kconfig cache strategies and turn them into mount options
>    "cache_strategy={disable|readahead|readaround}" suggested by Ted.
>    As the first step, cached pages can still be usable after cache is
>    disabled by remounting, and these pages will be fallen out over
>    time, which can be refined in the later version if some requirement
>    is needed. Update related document as well;
> 
>  o turn on CONFIG_EROFS_FS_SECURITY by default suggested by David;
> 
>  o kill CONFIG_EROFS_FS_IO_MAX_RETRIES and fold it into code; turn
>    EROFS_FS_USE_VM_MAP_RAM into a module parameter ("use_vmap")
>    suggested by David.
> 
> Changelog from v2:
>  o kill sbi->dev_name and clean up all failure handling in
>    fill_super() suggested by Al.
>    Note that the initialzation of managed_cache is now moved
>    after s_root is assigned since it's more preferred to iput()
>    in .put_super() and all inodes should be evicted before
>    the end of generic_shutdown_super(sb);
> 
>  o fold in the following staging patches (and thanks):
>    staging: erofs:converting all 'unsigned' to 'unsigned int'
>    staging: erofs: Remove function erofs_kill_sb()
>     - However it was revoked due to erofs_kill_sb reused...
>    staging: erofs: avoid opened loop codes
>    staging: erofs: support bmap
> 
>  o move EROFS_SUPER_MAGIC_V1 from linux/fs/erofs/erofs_fs.h to
>    include/uapi/linux/magic.h for userspace utilities.
> 
> Changelog from v1:
>  o resend the whole filesystem into a patchset suggested by Greg;
>  o code is more cleaner, especially for decompression frontend.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: Pavel Machek <pavel@denx.de>
> Cc: David Sterba <dsterba@suse.cz>
> Cc: Amir Goldstein <amir73il@gmail.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Darrick J . Wong <darrick.wong@oracle.com>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> Cc: Jan Kara <jack@suse.cz> 
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Chao Yu <yuchao0@huawei.com>
> Cc: Miao Xie <miaoxie@huawei.com>
> Cc: Li Guifu <bluce.liguifu@huawei.com>
> Cc: Fang Wei <fangwei1@huawei.com>
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> 
> 
> Gao Xiang (24):
>   erofs: add on-disk layout
>   erofs: add erofs in-memory stuffs
>   erofs: add super block operations
>   erofs: add raw address_space operations
>   erofs: add inode operations
>   erofs: support special inode
>   erofs: add directory operations
>   erofs: add namei functions
>   erofs: support tracepoint
>   erofs: update Kconfig and Makefile
>   erofs: introduce xattr & posixacl support
>   erofs: introduce tagged pointer
>   erofs: add compression indexes support
>   erofs: introduce superblock registration
>   erofs: introduce erofs shrinker
>   erofs: introduce workstation for decompression
>   erofs: introduce per-CPU buffers implementation
>   erofs: introduce pagevec for decompression subsystem
>   erofs: add erofs_allocpage()
>   erofs: introduce generic decompression backend
>   erofs: introduce LZ4 decompression inplace
>   erofs: introduce the decompression frontend
>   erofs: introduce cached decompression
>   erofs: add document
> 
>  Documentation/filesystems/erofs.txt |  225 +++++
>  fs/Kconfig                          |    1 +
>  fs/Makefile                         |    1 +
>  fs/erofs/Kconfig                    |   98 ++
>  fs/erofs/Makefile                   |   11 +
>  fs/erofs/compress.h                 |   62 ++
>  fs/erofs/data.c                     |  425 ++++++++
>  fs/erofs/decompressor.c             |  360 +++++++
>  fs/erofs/dir.c                      |  148 +++
>  fs/erofs/erofs_fs.h                 |  316 ++++++
>  fs/erofs/inode.c                    |  333 +++++++
>  fs/erofs/internal.h                 |  555 +++++++++++
>  fs/erofs/namei.c                    |  253 +++++
>  fs/erofs/super.c                    |  666 +++++++++++++
>  fs/erofs/tagptr.h                   |  110 +++
>  fs/erofs/utils.c                    |  335 +++++++
>  fs/erofs/xattr.c                    |  705 ++++++++++++++
>  fs/erofs/xattr.h                    |   94 ++
>  fs/erofs/zdata.c                    | 1405 +++++++++++++++++++++++++++
>  fs/erofs/zdata.h                    |  195 ++++
>  fs/erofs/zmap.c                     |  463 +++++++++
>  fs/erofs/zpvec.h                    |  159 +++
>  include/trace/events/erofs.h        |  256 +++++
>  include/uapi/linux/magic.h          |    1 +
>  24 files changed, 7177 insertions(+)
>  create mode 100644 Documentation/filesystems/erofs.txt
>  create mode 100644 fs/erofs/Kconfig
>  create mode 100644 fs/erofs/Makefile
>  create mode 100644 fs/erofs/compress.h
>  create mode 100644 fs/erofs/data.c
>  create mode 100644 fs/erofs/decompressor.c
>  create mode 100644 fs/erofs/dir.c
>  create mode 100644 fs/erofs/erofs_fs.h
>  create mode 100644 fs/erofs/inode.c
>  create mode 100644 fs/erofs/internal.h
>  create mode 100644 fs/erofs/namei.c
>  create mode 100644 fs/erofs/super.c
>  create mode 100644 fs/erofs/tagptr.h
>  create mode 100644 fs/erofs/utils.c
>  create mode 100644 fs/erofs/xattr.c
>  create mode 100644 fs/erofs/xattr.h
>  create mode 100644 fs/erofs/zdata.c
>  create mode 100644 fs/erofs/zdata.h
>  create mode 100644 fs/erofs/zmap.c
>  create mode 100644 fs/erofs/zpvec.h
>  create mode 100644 include/trace/events/erofs.h
>