MAINTAINERS: erofs: add EROFS webpage

Add a new `W:` field of the EROFS entry points to the documentation
site at <https://erofs.docs.kernel.org>.

In addition, update the in-tree documentation and Kconfig too.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231117085329.1624223-1-hsiangkao@linux.alibaba.com

erofs: fix inode metadata space layout description in documentation

Xattrs, extents, data inline are _placed after_, not _followed by_ the
corresponding inode. This patch fixes it.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20231010113915.436591-1-tiwei.btw@antgroup.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: update documentation

- update new features like bloom filter and DEFLATE.

- add documentation for the long xattr name prefixes, which was
landed upstream since v6.4.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230928134852.31118-1-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: set block size to the on-disk block size

Set the block size to that specified in on-disk superblock.

Also remove the hard constraint of PAGE_SIZE block size for the
uncompressed device backend. This constraint is temporarily remained
for compressed device and fscache backend, as there is more work needed
to handle the condition where the block size is not equal to PAGE_SIZE.

It is worth noting that the on-disk block size is read prior to
erofs_superblock_csum_verify(), as the read block size is needed in the
latter.

Besides, later we are going to make erofs refer to tar data blobs (which
is 512-byte aligned) for OCI containers, where the block size is 512
bytes. In this case, the 512-byte block size may not be adequate for a
directory to contain enough dirents. To fix this, we are also going to
introduce directory block size independent on the block size.

Due to we have already supported block size smaller than PAGE_SIZE now,
disable all these images with such separated directory block size until
we supported this feature later.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230313135309.75269-3-jefflexu@linux.alibaba.com
[ Gao Xiang: update documentation. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: add documentation for 'domain_id' mount option

Since the EROFS share domain feature for fscache mode has been available
since Linux v6.1, let's add documentation for 'domain_id' mount option.

Cc: linux-doc@vger.kernel.org
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230112065431.124926-2-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: enable large folios for fscache mode

Enable large folios for fscache mode. Enable this feature for
non-compressed format for now, until the compression part supports large
folios later.

One thing worth noting is that, the feature is not enabled for the meta
data routine since meta inodes don't need large folios for now, nor do
they support readahead yet.

Also document this new feature.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Link: https://lore.kernel.org/r/20221201074256.16639-3-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: update documentation

- Refine highlights for main features;

- Add multi-reference pclusters and fragment description.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20221130095605.4656-1-hsiangkao@linux.alibaba.com

erofs: update documentation

- refine the filesystem overview for better description of recent
new features like FSDAX and Fscache;

- add the new `fsid' mount option;

- fix some typos.

Link: https://lore.kernel.org/r/20220527070133.77962-1-hsiangkao@linux.alibaba.com
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: rename ctime to mtime

EROFS images should inherit modification time rather than change time,
since users and host tooling have no easy way to control change time.

To reflect the new timestamp meaning, i_ctime and i_ctime_nsec are
renamed to i_mtime and i_mtime_nsec.

Link: https://lore.kernel.org/r/20220311041829.3109511-1-dvander@google.com # v1
Signed-off-by: David Anderson <dvander@google.com>
[ Gao Xiang: update document as well. ]
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20220317114959.106787-1-hsiangkao@linux.alibaba.com # v2
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: add sysfs interface

Add sysfs interface to configure erofs related parameters later.

Link: https://lore.kernel.org/r/20211201145436.4357-1-huangjianan@oppo.com
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: add multiple device support

In order to support multi-layer container images, add multiple
device feature to EROFS. Two ways are available to use for now:

- Devices can be mapped into 32-bit global block address space;
- Device ID can be specified with the chunk indexes format.

Note that it assumes no extent would cross device boundary and mkfs
should take care of it seriously.

In the future, a dedicated device manager could be introduced then
thus extra devices can be automatically scanned by UUID as well.

Link: https://lore.kernel.org/r/20211014081010.43485-1-hsiangkao@linux.alibaba.com
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: introduce chunk-based file on-disk format

Currently, uncompressed data except for tail-packing inline is
consecutive on disk.

In order to support chunk-based data deduplication, add a new
corresponding inode data layout.

In the future, the data source of chunks can be either (un)compressed.

Link: https://lore.kernel.org/r/20210820100019.208490-1-hsiangkao@linux.alibaba.com
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: dax support for non-tailpacking regular file

DAX is quite useful for some VM use cases in order to save guest
memory extremely with minimal lightweight EROFS.

In order to prepare for such use cases, add preliminary dax support
for non-tailpacking regular files for now.

Tested with the DRAM-emulated PMEM and the EROFS image generated by
"mkfs.erofs -Enoinline_data enwik9.fsdax.img enwik9"

Link: https://lore.kernel.org/r/20210805003601.183063-3-hsiangkao@linux.alibaba.com
Cc: nvdimm@lists.linux.dev
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

erofs: update documentation about data compression

Add more description about (NON)HEAD lclusters, and the new big
pcluster feature.

Link: https://lore.kernel.org/r/20210511084414.21305-1-xiang@kernel.org
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>

erofs: fix broken illustration in documentation

Illustration was broken after ReST conversion by accident.
(checked by 'make SPHINXDIRS="filesystems" htmldocs')

Link: https://lore.kernel.org/r/20210510162506.28637-1-xiang@kernel.org
Fixes: e66d8631ddb3 ("docs: filesystems: convert erofs.txt to ReST")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Gao Xiang <xiang@kernel.org>

docs: filesystems: convert erofs.txt to ReST

- Add a SPDX header;
- Add a document title;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add table markups;
- Add lists markups;
- Add it to filesystems/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/402d1d2f7252b8a683f7a9c6867bc5428da64026.1581955849.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>