erofs: separate plain and compressed filesystems formally

The EROFS on-disk format uses a tiny, plain metadata design that
prioritizes performance and minimizes complex inconsistencies against
commo

erofs: separate plain and compressed filesystems formally

The EROFS on-disk format uses a tiny, plain metadata design that
prioritizes performance and minimizes complex inconsistencies against
common writable disk filesystems (almost all serious metadata
inconsistency cannot happen in well-designed immutable filesystems like
EROFS). EROFS deliberately avoids artificial design flaws to eliminate
serious security risks from untrusted remote sources by design,
although human-made implementation bugs can still happen sometimes.

Currently, there is no strict check to prevent compressed inodes,
especially LZ4-compressed inodes, from being read in plain filesystems.

Starting with erofs-utils 1.0 and Linux 5.3, LZ4_0PADDING sb feature
is automatically enabled for LZ4-compressed EROFS images to support
in-place decompression. Furthermore, since Linux 5.4 LTS is no longer
supported, we no longer need to handle ancient LZ4-compressed EROFS
images generated by erofs-utils prior to 1.0.

To formally distinguish different filesystem types for improved
security:

- Use the presence of LZ4_0PADDING or a non-zero
`dsb->u1.lz4_max_distance` as a marker for compressed filesystems
containing LZ4-compressed inodes only;

- For other algorithms, use `dsb->u1.available_compr_algs` bitmap.

Note: LZ4_0PADDING has been supported since Linux 5.4 (the first formal
kernel version), so exposing it via sysfs is no longer necessary and is
now deprecated (but remain it for five more years until 2031):

`dsb->u1` has been strictly non-zero for all EROFS images containing
compressed inodes starting with erofs-utils v1.3 and it is actually
a much better marker for compressed filesystems.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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erofs: tidy up synchronous decompression

- Get rid of `sbi->opt.max_sync_decompress_pages` since it's fixed as
3 all the time;

- Add Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES in bytes instead of in pa

erofs: tidy up synchronous decompression

- Get rid of `sbi->opt.max_sync_decompress_pages` since it's fixed as
3 all the time;

- Add Z_EROFS_MAX_SYNC_DECOMPRESS_BYTES in bytes instead of in pages,
since for non-4K pages, 3-page limitation makes no sense;

- Move `sync_decompress` to sbi to avoid unexpected remount impact;

- Fold z_erofs_is_sync_decompress() into its caller;

- Better description of sysfs entry `sync_decompress`.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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erofs: support to readahead dirent blocks in erofs_readdir()

This patch supports to readahead more blocks in erofs_readdir(), it can
enhance readdir performance in large direcotry.

readdir test in

erofs: support to readahead dirent blocks in erofs_readdir()

This patch supports to readahead more blocks in erofs_readdir(), it can
enhance readdir performance in large direcotry.

readdir test in a large directory which contains 12000 sub-files.

files_per_second
Before: 926385.54
After: 2380435.562

Meanwhile, let's introduces a new sysfs entry to control readahead
bytes to provide more flexible policy for readahead of readdir().
- location: /sys/fs/erofs/<disk>/dir_ra_bytes
- default value: 16384
- disable readahead: set the value to 0

Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250721021352.2495371-1-chao@kernel.org
[ Gao Xiang: minor styling adjustment. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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erofs: implement metadata compression

Thanks to the meta buffer infrastructure, metadata-compressed inodes are
just read from the metabox inode instead of the blockdevice (or backing
file) inode.

T

erofs: implement metadata compression

Thanks to the meta buffer infrastructure, metadata-compressed inodes are
just read from the metabox inode instead of the blockdevice (or backing
file) inode.

The same is true for shared extended attributes.

When metadata compression is enabled, inode numbers are divided from
on-disk NIDs because of non-LTS 32-bit application compatibility.

Co-developed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Bo Liu (OpenAnolis) <liubo03@inspur.com>
Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250722003229.2121752-1-hsiangkao@linux.alibaba.com

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erofs: support DEFLATE decompression by using Intel QAT

This patch introduces the use of the Intel QAT to offload EROFS data
decompression, aiming to improve the decompression performance.

A 285MiB

erofs: support DEFLATE decompression by using Intel QAT

This patch introduces the use of the Intel QAT to offload EROFS data
decompression, aiming to improve the decompression performance.

A 285MiB dataset is used with the following command to create EROFS
images with different cluster sizes:
$ mkfs.erofs -zdeflate,level=9 -C{4096,16384,65536,131072,262144}

Fio is used to test the following read patterns:
$ fio -filename=testfile -bs=4k -rw=read -name=job1
$ fio -filename=testfile -bs=4k -rw=randread -name=job1
$ fio -filename=testfile -bs=4k -rw=randread --io_size=14m -name=job1

Here are some performance numbers for reference:

Processors: Intel(R) Xeon(R) 6766E (144 cores)
Memory: 512 GiB

|-----------------------------------------------------------------------------|
| | Cluster size | sequential read | randread | small randread(5%) |
|-----------|--------------|-----------------|-----------|--------------------|
| Intel QAT | 4096 | 538 MiB/s | 112 MiB/s | 20.76 MiB/s |
| Intel QAT | 16384 | 699 MiB/s | 158 MiB/s | 21.02 MiB/s |
| Intel QAT | 65536 | 917 MiB/s | 278 MiB/s | 20.90 MiB/s |
| Intel QAT | 131072 | 1056 MiB/s | 351 MiB/s | 23.36 MiB/s |
| Intel QAT | 262144 | 1145 MiB/s | 431 MiB/s | 26.66 MiB/s |
| deflate | 4096 | 499 MiB/s | 108 MiB/s | 21.50 MiB/s |
| deflate | 16384 | 422 MiB/s | 125 MiB/s | 18.94 MiB/s |
| deflate | 65536 | 452 MiB/s | 159 MiB/s | 13.02 MiB/s |
| deflate | 131072 | 452 MiB/s | 177 MiB/s | 11.44 MiB/s |
| deflate | 262144 | 466 MiB/s | 194 MiB/s | 10.60 MiB/s |

Signed-off-by: Bo Liu <liubo03@inspur.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250522094931.28956-1-liubo03@inspur.com
[ Gao Xiang: refine the commit message. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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erofs: add sysfs node to drop internal caches

Add a sysfs node to drop compression-related caches, currently used to
drop in-memory pclusters and cached compressed folios.

Signed-off-by: Chunhai Gu

erofs: add sysfs node to drop internal caches

Add a sysfs node to drop compression-related caches, currently used to
drop in-memory pclusters and cached compressed folios.

Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241113041148.749129-1-guochunhai@vivo.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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Documentation/ABI: sysfs-fs-erofs: update supported features

Add missing feaures for sysfs-fs-erofs feature doc.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.a

Documentation/ABI: sysfs-fs-erofs: update supported features

Add missing feaures for sysfs-fs-erofs feature doc.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230209051128.10571-1-zbestahu@gmail.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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Documentation/ABI: sysfs-fs-erofs: Fix Sphinx errors

Fix the following warnings from "make htmldocs":

Documentation/ABI/testing/sysfs-fs-erofs:10:
ERROR: Unexpected indentation.
WARNING: Block

Documentation/ABI: sysfs-fs-erofs: Fix Sphinx errors

Fix the following warnings from "make htmldocs":

Documentation/ABI/testing/sysfs-fs-erofs:10:
ERROR: Unexpected indentation.
WARNING: Block quote ends without a blank line; unexpected unindent.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220324165918.22005-4-hdegoede@redhat.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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erofs: add sysfs node to control sync decompression strategy

Although readpage is a synchronous path, there will be no additional
kworker scheduling overhead in non-atomic contexts together with
dm-

erofs: add sysfs node to control sync decompression strategy

Although readpage is a synchronous path, there will be no additional
kworker scheduling overhead in non-atomic contexts together with
dm-verity.

Let's add a sysfs node to disable sync decompression as an option.

Link: https://lore.kernel.org/r/20211206143552.8384-1-huangjianan@oppo.com
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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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@ker

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>

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