linux-ext4 - Re: [v8 2/5] ext4: adds project ID support

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Message-Id: <2EE35986-B398-432E-92D4-EEF875381319@dilger.ca>
Date:	Thu, 8 Jan 2015 15:20:21 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Jan Kara <jack@...e.cz>
Cc:	Li Xi <pkuelelixi@...il.com>,
	Linux Filesystem Development List 
	<linux-fsdevel@...r.kernel.org>,
	ext4 development <linux-ext4@...r.kernel.org>,
	linux-api@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: Re: [v8 2/5] ext4: adds project ID support

On Jan 8, 2015, at 1:26 AM, Jan Kara <jack@...e.cz> wrote:
> On Tue 09-12-14 13:22:25, Li Xi wrote:
>> This patch adds a new internal field of ext4 inode to save project
>> identifier. Also a new flag EXT4_INODE_PROJINHERIT is added for
>> inheriting project ID from parent directory.
>  I have noticed one thing you apparently changed in v7 of the patch set.
> See below.
> 
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index 29c43e7..8bd1da9 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -377,16 +377,18 @@ struct flex_groups {
>> #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
>> #define EXT4_EOFBLOCKS_FL		0x00400000 /* Blocks allocated beyond EOF */
>> #define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
>> +#define EXT4_PROJINHERIT_FL		FS_PROJINHERIT_FL /* Create with parents projid */
>  How did FS_PROJINHERIT_FL get here? There used to be 0x20000000 in older
> version of the patch set which is correct - this definition is defining
> ext4 on-disk format. As such it is an ext4 specific flag and should be
> definined to a fixed constant independed of any other filesystem. It seems
> you are somewhat mixing what is an on-disk format flag value and what is a
> flag value passed from userspace. These two may be different things and
> you need to convert between the values when getting / setting flags...

Currently the EXT4_*_FL and FS_*_FL values are all identical, and there
is no reason to change that before it is actually needed.  Since the
FS_PROJINHERIT_FL is used via chattr/lsattr from userspace, this value
must also be kept the same in the future to avoid API breakage, so there
is no reason to worry about incompatibilities.

See also the [v8 5/5] patch, which is changing the EXT4_*_FL values to
use FS_*_FL constants, where applicable, so that it is more clear that
these values need to be the same.

Cheers, Andreas





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