From: Gao Xiang <hsiangkao@aol.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Gao Xiang <gaoxiang25@huawei.com>, Jan Kara <jack@suse.cz>,
Chao Yu <yuchao0@huawei.com>, 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>,
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>,
Li Guifu <bluce.liguifu@huawei.com>,
Fang Wei <fangwei1@huawei.com>,
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 03/24] erofs: add super block operations
Date: Sun, 1 Sep 2019 16:54:55 +0800 [thread overview]
Message-ID: <20190901085452.GA4663@hsiangkao-HP-ZHAN-66-Pro-G1> (raw)
In-Reply-To: <20190829101545.GC20598@infradead.org>
Hi Christoph,
Here is also my redo-ed comments...
On Thu, Aug 29, 2019 at 03:15:45AM -0700, Christoph Hellwig wrote:
> On Fri, Aug 02, 2019 at 08:53:26PM +0800, Gao Xiang wrote:
> > +static int __init erofs_init_inode_cache(void)
> > +{
> > + erofs_inode_cachep = kmem_cache_create("erofs_inode",
> > + sizeof(struct erofs_vnode), 0,
> > + SLAB_RECLAIM_ACCOUNT,
> > + init_once);
> > +
> > + return erofs_inode_cachep ? 0 : -ENOMEM;
>
> Please just use normal if/else. Also having this function seems
> entirely pointless.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-7-hsiangkao@aol.com/
>
> > +static void erofs_exit_inode_cache(void)
> > +{
> > + kmem_cache_destroy(erofs_inode_cachep);
> > +}
>
> Same for this one.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-7-hsiangkao@aol.com/
>
> > +static void free_inode(struct inode *inode)
>
> Please use an erofs_ prefix for all your functions.
free_inode and most short, common static functions are fixed in
https://lore.kernel.org/r/20190901055130.30572-19-hsiangkao@aol.com/
For all non-static functions, all are prefixed with "erofs_"
>
> > +{
> > + struct erofs_vnode *vi = EROFS_V(inode);
>
> Why is this called vnode instead of inode? That seems like a rather
> odd naming for a Linux file system.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-8-hsiangkao@aol.com/
>
> > +
> > + /* be careful RCU symlink path (see ext4_inode_info->i_data)! */
> > + if (is_inode_fast_symlink(inode))
> > + kfree(inode->i_link);
>
> is_inode_fast_symlink only shows up in a later patch. And really
> obsfucates the check here in the only caller as you can just do an
> unconditional kfree here - i_link will be NULL except for the case
> where you explicitly set it.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-10-hsiangkao@aol.com/
and with my following comments....
https://lore.kernel.org/r/20190831005446.GA233871@architecture4/
>
> Also this code is nothing like ext4, so the code seems a little confusing.
>
> > +static bool check_layout_compatibility(struct super_block *sb,
> > + struct erofs_super_block *layout)
> > +{
> > + const unsigned int requirements = le32_to_cpu(layout->requirements);
>
> Why is the variable name for the on-disk subperblock layout? We usually
> still calls this something with sb in the name, e.g. dsb. for disk
> super block.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-12-hsiangkao@aol.com/
>
> > + EROFS_SB(sb)->requirements = requirements;
> > +
> > + /* check if current kernel meets all mandatory requirements */
> > + if (requirements & (~EROFS_ALL_REQUIREMENTS)) {
> > + errln("unidentified requirements %x, please upgrade kernel version",
> > + requirements & ~EROFS_ALL_REQUIREMENTS);
> > + return false;
> > + }
> > + return true;
>
> Note that normally we call this features, but that doesn't really
> matter too much.
No modification at this... (some comments already right here...)
20 /* 128-byte erofs on-disk super block */
21 struct erofs_super_block {
...
24 __le32 features; /* (aka. feature_compat) */
...
38 __le32 requirements; /* (aka. feature_incompat) */
...
41 };
>
> > +static int superblock_read(struct super_block *sb)
> > +{
> > + struct erofs_sb_info *sbi;
> > + struct buffer_head *bh;
> > + struct erofs_super_block *layout;
> > + unsigned int blkszbits;
> > + int ret;
> > +
> > + bh = sb_bread(sb, 0);
>
> Is there any good reasons to use buffer heads like this in new code
> vs directly using bios?
As you said, I want it in the page cache.
The reason "why not use read_mapping_page or similar?" is simply
read_mapping_page -> .readpage -> (for bdev inode) block_read_full_page
-> create_page_buffers anyway...
sb_bread haven't obsoleted... It has similar function though...
>
> > +
> > + sbi->blocks = le32_to_cpu(layout->blocks);
> > + sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);
> > + sbi->islotbits = ffs(sizeof(struct erofs_inode_v1)) - 1;
> > + sbi->root_nid = le16_to_cpu(layout->root_nid);
> > + sbi->inos = le64_to_cpu(layout->inos);
> > +
> > + sbi->build_time = le64_to_cpu(layout->build_time);
> > + sbi->build_time_nsec = le32_to_cpu(layout->build_time_nsec);
> > +
> > + memcpy(&sb->s_uuid, layout->uuid, sizeof(layout->uuid));
> > + memcpy(sbi->volume_name, layout->volume_name,
> > + sizeof(layout->volume_name));
>
> s_uuid should preferably be a uuid_t (assuming it is a real BE uuid,
> if it is le it should be a guid_t).
For this case, I have no idea how to deal with...
I have little knowledge about this uuid stuff, so I just copied
from f2fs... (Could be no urgent of this field...)
>
> > +/* set up default EROFS parameters */
> > +static void default_options(struct erofs_sb_info *sbi)
> > +{
> > +}
>
> No need to add an empty function.
My fault of spilting patches...
>
> > +static int erofs_fill_super(struct super_block *sb, void *data, int silent)
> > +{
> > + struct inode *inode;
> > + struct erofs_sb_info *sbi;
> > + int err;
> > +
> > + infoln("fill_super, device -> %s", sb->s_id);
> > + infoln("options -> %s", (char *)data);
>
> That is some very verbose debug info. We usually don't add that and
> let people trace the function instead. Also you should probably
> implement the new mount API.
> new mount API.
Fixed in
https://lore.kernel.org/r/20190901055130.30572-13-hsiangkao@aol.com/
(For new mount API,
https://lore.kernel.org/r/20190721040547.GF17978@ZenIV.linux.org.uk/
, I will a look later)
>
> > +static void erofs_kill_sb(struct super_block *sb)
> > +{
> > + struct erofs_sb_info *sbi;
> > +
> > + WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
> > + infoln("unmounting for %s", sb->s_id);
> > +
> > + kill_block_super(sb);
> > +
> > + sbi = EROFS_SB(sb);
> > + if (!sbi)
> > + return;
> > + kfree(sbi);
> > + sb->s_fs_info = NULL;
> > +}
>
> Why is this needed? You can just free your sb privatte information in
> ->put_super and wire up kill_block_super as the ->kill_sb method
> directly.
The background is Al's comments in erofs v2....
(which simplify erofs_fill_super logic)
https://lore.kernel.org/r/20190720224955.GD17978@ZenIV.linux.org.uk/
with a specific notation...
https://lore.kernel.org/r/20190721040547.GF17978@ZenIV.linux.org.uk/
"
> OTOH, for the case of NULL ->s_root ->put_super() won't be called
> at all, so in that case you need it directly in ->kill_sb().
"
Thanks,
Gao Xiang
next prev parent reply other threads:[~2019-09-01 8:55 UTC|newest]
Thread overview: 70+ 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
2019-08-29 9:59 ` Christoph Hellwig
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
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
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 Gao Xiang
2019-08-02 12:53 ` [PATCH v6 03/24] erofs: add super block operations Gao Xiang
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 [this message]
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
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 Gao Xiang
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
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
2019-08-29 10:25 ` Christoph Hellwig
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
2019-08-29 10:28 ` Christoph Hellwig
2019-08-29 11:28 ` 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
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