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From: Christoph Hellwig <hch@infradead.org>
To: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jan Kara <jack@suse.cz>, Dave Chinner <david@fromorbit.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Miao Xie <miaoxie@huawei.com>,
	devel@driverdev.osuosl.org,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	Christoph Hellwig <hch@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Amir Goldstein <amir73il@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Jaegeuk Kim <jaegeuk@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
	Pavel Machek <pavel@denx.de>, David Sterba <dsterba@suse.cz>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-fsdevel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH v6 01/24] erofs: add on-disk layout
Date: Thu, 29 Aug 2019 02:59:54 -0700
Message-ID: <20190829095954.GB20598@infradead.org> (raw)
In-Reply-To: <20190802125347.166018-2-gaoxiang25@huawei.com>

> --- /dev/null
> +++ b/fs/erofs/erofs_fs.h
> @@ -0,0 +1,316 @@
> +/* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
> +/*
> + * linux/fs/erofs/erofs_fs.h

Please remove the pointless file names in the comment headers.

> +struct erofs_super_block {
> +/*  0 */__le32 magic;           /* in the little endian */
> +/*  4 */__le32 checksum;        /* crc32c(super_block) */
> +/*  8 */__le32 features;        /* (aka. feature_compat) */
> +/* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */

Please remove all the byte offset comments.  That is something that can
easily be checked with gdb or pahole.

> +/* 64 */__u8 volume_name[16];   /* volume name */
> +/* 80 */__le32 requirements;    /* (aka. feature_incompat) */
> +
> +/* 84 */__u8 reserved2[44];
> +} __packed;                     /* 128 bytes */

Please don't add __packed.  In this case I think you don't need it
(but double check with pahole), but even if you would need it using
proper padding fields and making sure all fields are naturally aligned
will give you much better code generation on architectures that don't
support native unaligned access.

> +/*
> + * erofs inode data mapping:
> + * 0 - inode plain without inline data A:
> + * inode, [xattrs], ... | ... | no-holed data
> + * 1 - inode VLE compression B (legacy):
> + * inode, [xattrs], extents ... | ...
> + * 2 - inode plain with inline data C:
> + * inode, [xattrs], last_inline_data, ... | ... | no-holed data
> + * 3 - inode compression D:
> + * inode, [xattrs], map_header, extents ... | ...
> + * 4~7 - reserved
> + */
> +enum {
> +	EROFS_INODE_FLAT_PLAIN,

This one doesn't actually seem to be used.

> +	EROFS_INODE_FLAT_COMPRESSION_LEGACY,

why are we adding a legacy field to a brand new file system?

> +	EROFS_INODE_FLAT_INLINE,
> +	EROFS_INODE_FLAT_COMPRESSION,
> +	EROFS_INODE_LAYOUT_MAX

It seems like these come from the on-disk format, in which case they
should have explicit values assigned to them.

Btw, I think it generally helps file system implementation quality
if you use a separate header for the on-disk structures vs in-memory
structures, as that keeps it clear in everyones mind what needs to
stay persistent and what can be chenged easily.

> +static bool erofs_inode_is_data_compressed(unsigned int datamode)
> +{
> +	if (datamode == EROFS_INODE_FLAT_COMPRESSION)
> +		return true;
> +	return datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
> +}

This looks like a really obsfucated way to write:

	return datamode == EROFS_INODE_FLAT_COMPRESSION ||
		datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;

> +/* 28 */__le32 i_reserved2;
> +} __packed;

Sane comment as above.

> +
> +/* 32 bytes on-disk inode */
> +#define EROFS_INODE_LAYOUT_V1   0
> +/* 64 bytes on-disk inode */
> +#define EROFS_INODE_LAYOUT_V2   1
> +
> +struct erofs_inode_v2 {
> +/*  0 */__le16 i_advise;

Why do we have two inode version in a newly added file system?

> +#define ondisk_xattr_ibody_size(count)	({\
> +	u32 __count = le16_to_cpu(count); \
> +	((__count) == 0) ? 0 : \
> +	sizeof(struct erofs_xattr_ibody_header) + \
> +		sizeof(__u32) * ((__count) - 1); })

This would be much more readable as a function.

> +#define EROFS_XATTR_ENTRY_SIZE(entry) EROFS_XATTR_ALIGN( \
> +	sizeof(struct erofs_xattr_entry) + \
> +	(entry)->e_name_len + le16_to_cpu((entry)->e_value_size))

Same here.

> +/* available compression algorithm types */
> +enum {
> +	Z_EROFS_COMPRESSION_LZ4,
> +	Z_EROFS_COMPRESSION_MAX
> +};

Seems like an on-disk value again that should use explicitly assigned
numbers.

  reply index

Thread overview: 159+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 12:53 [PATCH v6 00/24] erofs: promote erofs from staging gaoxiang25
2019-08-02 12:53 ` [PATCH v6 01/24] erofs: add on-disk layout gaoxiang25
2019-08-29  9:59   ` Christoph Hellwig [this message]
2019-08-29 10:32     ` Gao Xiang
2019-08-29 10:36       ` Christoph Hellwig
2019-08-29 10:58         ` Gao Xiang
2019-08-29 15:58       ` Joe Perches
2019-08-29 17:26         ` Gao Xiang
2019-08-30 12:07         ` David Sterba
2019-08-30 12:18           ` Gao Xiang via Linux-erofs
2019-09-02  8:43           ` Pavel Machek
2019-09-02 14:07             ` David Sterba
2019-09-03 11:27               ` Pavel Machek
2019-08-29 15:41     ` Gao Xiang
2019-09-01  7:54     ` Gao Xiang via Linux-erofs
2019-09-02 12:45       ` Christoph Hellwig
2019-09-02 13:02         ` Gao Xiang
2019-09-02  8:40     ` Pavel Machek
2019-09-02 10:35       ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 02/24] erofs: add erofs in-memory stuffs gaoxiang25
2019-08-02 12:53 ` [PATCH v6 03/24] erofs: add super block operations gaoxiang25
2019-08-29 10:15   ` Christoph Hellwig
2019-08-29 10:50     ` Gao Xiang
2019-08-30 16:39       ` Christoph Hellwig
2019-08-30 17:15         ` Gao Xiang
2019-08-31  0:54           ` Gao Xiang
2019-08-31  6:34           ` Amir Goldstein
2019-08-31  6:48             ` Gao Xiang
2019-09-01  8:54     ` Gao Xiang via Linux-erofs
2019-09-02 12:51       ` Christoph Hellwig
2019-09-02 14:43         ` Gao Xiang
2019-09-02 15:19           ` Christoph Hellwig
2019-09-02 15:24             ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 04/24] erofs: add raw address_space operations gaoxiang25
2019-08-29 10:17   ` Christoph Hellwig
2019-08-29 11:46     ` Gao Xiang
2019-08-30 16:40       ` Christoph Hellwig
2019-08-30 17:23         ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 05/24] erofs: add inode operations gaoxiang25
2019-08-29 10:24   ` Christoph Hellwig
2019-08-29 11:59     ` Gao Xiang
2019-08-30 16:42       ` Christoph Hellwig
2019-08-30 18:46         ` Gao Xiang
2019-09-01  9:34     ` Gao Xiang via Linux-erofs
2019-09-02 12:53       ` Christoph Hellwig
2019-09-02 13:43       ` David Sterba
2019-09-02 13:55         ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 06/24] erofs: support special inode gaoxiang25
2019-08-29 10:25   ` Christoph Hellwig
2019-09-01  9:39     ` Gao Xiang via Linux-erofs
2019-08-02 12:53 ` [PATCH v6 07/24] erofs: add directory operations gaoxiang25
2019-08-02 12:53 ` [PATCH v6 08/24] erofs: add namei functions gaoxiang25
2019-08-29 10:28   ` Christoph Hellwig
2019-08-29 11:28     ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 09/24] erofs: support tracepoint gaoxiang25
2019-08-02 12:53 ` [PATCH v6 10/24] erofs: update Kconfig and Makefile gaoxiang25
2019-08-02 12:53 ` [PATCH v6 11/24] erofs: introduce xattr & posixacl support gaoxiang25
2019-08-02 12:53 ` [PATCH v6 12/24] erofs: introduce tagged pointer gaoxiang25
2019-08-02 12:53 ` [PATCH v6 13/24] erofs: add compression indexes support gaoxiang25
2019-08-02 12:53 ` [PATCH v6 14/24] erofs: introduce superblock registration gaoxiang25
2019-08-02 12:53 ` [PATCH v6 15/24] erofs: introduce erofs shrinker gaoxiang25
2019-08-02 12:53 ` [PATCH v6 16/24] erofs: introduce workstation for decompression gaoxiang25
2019-08-02 12:53 ` [PATCH v6 17/24] erofs: introduce per-CPU buffers implementation gaoxiang25
2019-08-02 12:53 ` [PATCH v6 18/24] erofs: introduce pagevec for decompression subsystem gaoxiang25
2019-08-02 12:53 ` [PATCH v6 19/24] erofs: add erofs_allocpage() gaoxiang25
2019-08-02 12:53 ` [PATCH v6 20/24] erofs: introduce generic decompression backend gaoxiang25
2019-08-02 12:53 ` [PATCH v6 21/24] erofs: introduce LZ4 decompression inplace gaoxiang25
2019-08-02 12:53 ` [PATCH v6 22/24] erofs: introduce the decompression frontend gaoxiang25
2019-08-02 12:53 ` [PATCH v6 23/24] erofs: introduce cached decompression gaoxiang25
2019-08-02 12:53 ` [PATCH v6 24/24] erofs: add document gaoxiang25
2019-09-01  5:51 ` [PATCH 00/21] erofs: patchset addressing Christoph's comments Gao Xiang via Linux-erofs
2019-09-01  5:51   ` [PATCH 01/21] erofs: remove all the byte offset comments Gao Xiang via Linux-erofs
2019-09-02 12:05     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 02/21] erofs: on-disk format should have explicitly assigned numbers Gao Xiang via Linux-erofs
2019-09-02 12:05     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 03/21] erofs: some macros are much more readable as a function Gao Xiang via Linux-erofs
2019-09-02 12:06     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 04/21] erofs: kill __packed for on-disk structures Gao Xiang via Linux-erofs
2019-09-02 12:06     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 05/21] erofs: update erofs_inode_is_data_compressed helper Gao Xiang via Linux-erofs
2019-09-02 12:07     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 06/21] erofs: kill erofs_{init,exit}_inode_cache Gao Xiang via Linux-erofs
2019-09-02 12:09     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 07/21] erofs: use erofs_inode naming Gao Xiang via Linux-erofs
2019-09-02 12:10     ` Christoph Hellwig
2019-09-02 12:13       ` Gao Xiang
2019-09-02 12:47         ` Christoph Hellwig
2019-09-02 13:33           ` Gao Xiang
2019-09-01  5:51   ` [PATCH 08/21] erofs: update comments in inode.c Gao Xiang via Linux-erofs
2019-09-01  5:51   ` [PATCH 09/21] erofs: update erofs symlink stuffs Gao Xiang via Linux-erofs
2019-09-02 12:11     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 10/21] erofs: kill is_inode_layout_compression() Gao Xiang via Linux-erofs
2019-09-02 12:11     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 11/21] erofs: use dsb instead of layout for ondisk super_block Gao Xiang via Linux-erofs
2019-09-02 12:12     ` Christoph Hellwig
2019-09-02 12:15       ` Gao Xiang
2019-09-01  5:51   ` [PATCH 12/21] erofs: kill verbose debug info in erofs_fill_super Gao Xiang via Linux-erofs
2019-09-02 12:14     ` Christoph Hellwig
2019-09-02 12:18       ` Gao Xiang
2019-09-01  5:51   ` [PATCH 13/21] erofs: simplify erofs_grab_bio() since bio_alloc() never fail Gao Xiang via Linux-erofs
2019-09-02 12:20     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 14/21] erofs: kill prio and nofail of erofs_get_meta_page() Gao Xiang via Linux-erofs
2019-09-02 12:21     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 15/21] erofs: kill __submit_bio() Gao Xiang via Linux-erofs
2019-09-01  5:51   ` [PATCH 16/21] erofs: kill magic underscores Gao Xiang via Linux-erofs
2019-09-02 12:26     ` Christoph Hellwig
2019-09-02 12:39       ` Gao Xiang
2019-09-02 12:54         ` Christoph Hellwig
2019-09-02 13:38           ` Gao Xiang
2019-09-01  5:51   ` [PATCH 17/21] erofs: use a switch statement when dealing with the file modes Gao Xiang via Linux-erofs
2019-09-02 12:27     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 18/21] erofs: add "erofs_" prefix for common and short functions Gao Xiang via Linux-erofs
2019-09-02 12:28     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 19/21] erofs: kill all erofs specific fault injection Gao Xiang via Linux-erofs
2019-09-02 12:28     ` Christoph Hellwig
2019-09-01  5:51   ` [PATCH 20/21] erofs: kill use_vmap module parameter Gao Xiang via Linux-erofs
2019-09-02 12:31     ` Christoph Hellwig
2019-09-02 12:43       ` Gao Xiang
2019-09-01  5:51   ` [PATCH 21/21] erofs: save one level of indentation Gao Xiang via Linux-erofs
2019-09-02 12:31     ` Christoph Hellwig
2019-09-02 12:46   ` [PATCH 00/21] erofs: patchset addressing Christoph's comments Christoph Hellwig
2019-09-02 14:24     ` Gao Xiang
2019-09-02 15:23       ` Christoph Hellwig
2019-09-02 15:50         ` Gao Xiang
2019-09-03  6:58           ` Christoph Hellwig
2019-09-03  8:17             ` Gao Xiang
2019-09-03 15:37               ` Christoph Hellwig
2019-09-03 15:43                 ` Gao Xiang via Linux-erofs
2019-09-04  2:08   ` [PATCH v2 00/25] " Gao Xiang
2019-09-04  2:08     ` [PATCH v2 01/25] erofs: remove all the byte offset comments Gao Xiang
2019-09-04  2:08     ` [PATCH v2 02/25] erofs: on-disk format should have explicitly assigned numbers Gao Xiang
2019-09-04  2:08     ` [PATCH v2 03/25] erofs: some macros are much more readable as a function Gao Xiang
2019-09-04  2:08     ` [PATCH v2 04/25] erofs: kill __packed for on-disk structures Gao Xiang
2019-09-04  2:08     ` [PATCH v2 05/25] erofs: update erofs_inode_is_data_compressed helper Gao Xiang
2019-09-04  2:08     ` [PATCH v2 06/25] erofs: use feature_incompat rather than requirements Gao Xiang
2019-09-04  2:08     ` [PATCH v2 07/25] erofs: better naming for erofs inode related stuffs Gao Xiang
2019-09-04  2:08     ` [PATCH v2 08/25] erofs: kill erofs_{init,exit}_inode_cache Gao Xiang
2019-09-04  2:08     ` [PATCH v2 09/25] erofs: use erofs_inode naming Gao Xiang
2019-09-04  2:08     ` [PATCH v2 10/25] erofs: update erofs_fs.h comments Gao Xiang
2019-09-04  2:08     ` [PATCH v2 11/25] erofs: update comments in inode.c Gao Xiang
2019-09-04  2:08     ` [PATCH v2 12/25] erofs: better erofs symlink stuffs Gao Xiang
2019-09-04  2:09     ` [PATCH v2 13/25] erofs: use dsb instead of layout for ondisk super_block Gao Xiang
2019-09-04  2:09     ` [PATCH v2 14/25] erofs: kill verbose debug info in erofs_fill_super Gao Xiang
2019-09-04  2:09     ` [PATCH v2 15/25] erofs: localize erofs_grab_bio() Gao Xiang
2019-09-04  2:09     ` [PATCH v2 16/25] erofs: kill prio and nofail of erofs_get_meta_page() Gao Xiang
2019-09-04  2:09     ` [PATCH v2 17/25] erofs: kill __submit_bio() Gao Xiang
2019-09-04  2:09     ` [PATCH v2 18/25] erofs: add "erofs_" prefix for common and short functions Gao Xiang
2019-09-04  2:09     ` [PATCH v2 19/25] erofs: kill all erofs specific fault injection Gao Xiang
2019-09-04  2:09     ` [PATCH v2 20/25] erofs: kill use_vmap module parameter Gao Xiang
2019-09-04  2:09     ` [PATCH v2 21/25] erofs: save one level of indentation Gao Xiang
2019-09-04  2:09     ` [PATCH v2 22/25] erofs: rename errln/infoln/debugln to erofs_{err, info, dbg} Gao Xiang
2019-09-04  2:09     ` [PATCH v2 23/25] erofs: use read_mapping_page instead of sb_bread Gao Xiang
2019-09-04  2:09     ` [PATCH v2 24/25] erofs: always use iget5_locked Gao Xiang
2019-09-04  2:09     ` [PATCH v2 25/25] erofs: use read_cache_page_gfp for erofs_get_meta_page Gao Xiang
2019-09-04  3:27     ` [PATCH v2 00/25] erofs: patchset addressing Christoph's comments Chao Yu
2019-09-05  1:03       ` Gao Xiang via Linux-erofs
2019-09-05 11:30         ` Christoph Hellwig
2019-09-04  5:16     ` Christoph Hellwig
2019-09-04  6:08       ` Gao Xiang via Linux-erofs

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