From: Gao Xiang <hsiangkao@aol.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: devel@driverdev.osuosl.org,
Stephen Rothwell <sfr@canb.auug.org.au>,
linux-erofs@lists.ozlabs.org, Jan Kara <jack@suse.cz>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Amir Goldstein <amir73il@gmail.com>,
Dave Chinner <david@fromorbit.com>,
LKML <linux-kernel@vger.kernel.org>,
Theodore Ts'o <tytso@mit.edu>, Pavel Machek <pavel@denx.de>,
David Sterba <dsterba@suse.cz>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jaegeuk Kim <jaegeuk@kernel.org>,
linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Miao Xie <miaoxie@huawei.com>
Subject: Re: [PATCH v6 01/24] erofs: add on-disk layout
Date: Sun, 1 Sep 2019 15:54:11 +0800 [thread overview]
Message-ID: <20190901075240.GA2938@hsiangkao-HP-ZHAN-66-Pro-G1> (raw)
In-Reply-To: <20190829095954.GB20598@infradead.org>
Hi Christoph,
Sorry about my first response, sincerely...
Here is my redo-ed comments to all your suggestions...
On Thu, Aug 29, 2019 at 02:59:54AM -0700, Christoph Hellwig wrote:
> > --- /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.
Has already fixed in the latest version, and I will resend
the whole v9 addressing all suggestions from you these days...
However it's somewhat hard to spilt the whole code prefectly
since erofs is ~7KLOC code and linux-fsdevel mailing list
have some limitation, I have spilted it in the form of features...
>
> > +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.
fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-2-hsiangkao@aol.com/
>
> > +/* 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.
fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-5-hsiangkao@aol.com/
>
> > +/*
> > + * 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.
It could be better has a name though, because 1) erofs.mkfs uses this
definition explicitly, and we keep this on-disk definition erofs_fs.h
file up with erofs-utils.
2) For kernel use, first we have,
datamode < EROFS_INODE_LAYOUT_MAX; and
!erofs_inode_is_data_compressed, so there are only two mode here,
1) EROFS_INODE_FLAT_INLINE,
2) EROFS_INODE_FLAT_PLAIN
if its datamode isn't EROFS_INODE_FLAT_INLINE (tail-end block packing),
it should be EROFS_INODE_FLAT_PLAIN.
The detailed logic in erofs_read_inode and
erofs_map_blocks_flatmode....
>
> > + EROFS_INODE_FLAT_COMPRESSION_LEGACY,
>
> why are we adding a legacy field to a brand new file system?
The difference is just EROFS_INODE_FLAT_COMPRESSION_LEGACY doesn't
have z_erofs_map_header, so it only supports default (4k clustersize)
fixed-sized output compression rather than per-file setting, nothing
special at all...
>
> > + 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.
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-3-hsiangkao@aol.com/
>
> 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.
All fields in this file are on-disk representation by design
(no logic for in-memory presentation).
>
> > +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;
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-6-hsiangkao@aol.com/
>
> > +/* 28 */__le32 i_reserved2;
> > +} __packed;
>
> Sane comment as above.
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-5-hsiangkao@aol.com/
>
> > +
> > +/* 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?
There is no new or old, both can be used for the current EROFS in one image.
v2 is an exhanced on-disk inode form, it has 64 bytes,
v1 is more reduced one, which is already suitable for Android use case.
>
> > +#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.
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-4-hsiangkao@aol.com/
>
> > +#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.
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-4-hsiangkao@aol.com/
>
> > +/* 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.
Fixed in
https://lore.kernel.org/linux-fsdevel/20190901055130.30572-3-hsiangkao@aol.com/
Thanks,
Gao Xiang
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next prev parent reply other threads:[~2019-09-01 7:54 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 12:53 [PATCH v6 00/24] erofs: promote erofs from staging Gao Xiang
2019-08-02 12:53 ` [PATCH v6 01/24] erofs: add on-disk layout Gao Xiang
[not found] ` <20190829095954.GB20598@infradead.org>
2019-09-01 7:54 ` Gao Xiang [this message]
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
[not found] ` <20190829103252.GA64893@architecture4>
[not found] ` <67d6efbbc9ac6db23215660cb970b7ef29dc0c1d.camel@perches.com>
[not found] ` <20190830120714.GN2752@twin.jikos.cz>
2019-09-02 8:43 ` Pavel Machek
2019-09-02 14:07 ` David Sterba
2019-09-03 11:27 ` Pavel Machek
2019-08-02 12:53 ` [PATCH v6 02/24] erofs: add erofs in-memory stuffs Gao Xiang
2019-08-02 12:53 ` [PATCH v6 03/24] erofs: add super block operations Gao Xiang
[not found] ` <20190829101545.GC20598@infradead.org>
[not found] ` <20190829105048.GB64893@architecture4>
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
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 Gao Xiang
[not found] ` <20190829101721.GD20598@infradead.org>
[not found] ` <20190829114610.GF64893@architecture4>
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 Gao Xiang
[not found] ` <20190829102426.GE20598@infradead.org>
[not found] ` <20190829115922.GG64893@architecture4>
2019-08-30 16:42 ` Christoph Hellwig
2019-08-30 18:46 ` Gao Xiang
2019-09-01 9:34 ` Gao Xiang
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 Gao Xiang
[not found] ` <20190829102503.GF20598@infradead.org>
2019-09-01 9:39 ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 07/24] erofs: add directory operations Gao Xiang
2019-08-02 12:53 ` [PATCH v6 08/24] erofs: add namei functions Gao Xiang
2019-08-02 12:53 ` [PATCH v6 09/24] erofs: support tracepoint Gao Xiang
2019-08-02 12:53 ` [PATCH v6 10/24] erofs: update Kconfig and Makefile Gao Xiang
2019-08-02 12:53 ` [PATCH v6 11/24] erofs: introduce xattr & posixacl support Gao Xiang
2019-08-02 12:53 ` [PATCH v6 12/24] erofs: introduce tagged pointer Gao Xiang
2019-08-02 12:53 ` [PATCH v6 13/24] erofs: add compression indexes support Gao Xiang
2019-08-02 12:53 ` [PATCH v6 14/24] erofs: introduce superblock registration Gao Xiang
2019-08-02 12:53 ` [PATCH v6 15/24] erofs: introduce erofs shrinker Gao Xiang
2019-08-02 12:53 ` [PATCH v6 16/24] erofs: introduce workstation for decompression Gao Xiang
2019-08-02 12:53 ` [PATCH v6 17/24] erofs: introduce per-CPU buffers implementation Gao Xiang
2019-08-02 12:53 ` [PATCH v6 18/24] erofs: introduce pagevec for decompression subsystem Gao Xiang
2019-08-02 12:53 ` [PATCH v6 19/24] erofs: add erofs_allocpage() Gao Xiang
2019-08-02 12:53 ` [PATCH v6 20/24] erofs: introduce generic decompression backend Gao Xiang
2019-08-02 12:53 ` [PATCH v6 21/24] erofs: introduce LZ4 decompression inplace Gao Xiang
2019-08-02 12:53 ` [PATCH v6 22/24] erofs: introduce the decompression frontend Gao Xiang
2019-08-02 12:53 ` [PATCH v6 23/24] erofs: introduce cached decompression Gao Xiang
2019-08-02 12:53 ` [PATCH v6 24/24] erofs: add document Gao Xiang
2019-09-01 5:51 ` [PATCH 00/21] erofs: patchset addressing Christoph's comments Gao Xiang
2019-09-01 5:51 ` [PATCH 01/21] erofs: remove all the byte offset comments Gao Xiang
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
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
2019-09-02 12:06 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 04/21] erofs: kill __packed for on-disk structures Gao Xiang
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
2019-09-02 12:07 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 06/21] erofs: kill erofs_{init,exit}_inode_cache Gao Xiang
2019-09-02 12:09 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 07/21] erofs: use erofs_inode naming Gao Xiang
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
2019-09-01 5:51 ` [PATCH 09/21] erofs: update erofs symlink stuffs Gao Xiang
2019-09-02 12:11 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 10/21] erofs: kill is_inode_layout_compression() Gao Xiang
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
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
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
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
2019-09-02 12:21 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 15/21] erofs: kill __submit_bio() Gao Xiang
2019-09-01 5:51 ` [PATCH 16/21] erofs: kill magic underscores Gao Xiang
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
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
2019-09-02 12:28 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 19/21] erofs: kill all erofs specific fault injection Gao Xiang
2019-09-02 12:28 ` Christoph Hellwig
2019-09-01 5:51 ` [PATCH 20/21] erofs: kill use_vmap module parameter Gao Xiang
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
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
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
2019-09-05 11:30 ` Christoph Hellwig
2019-09-04 5:16 ` Christoph Hellwig
2019-09-04 6:08 ` Gao Xiang
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