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

From: Jan Kara <jack@suse.cz>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Jan Kara <jack@suse.cz>, Li Xi <pkuelelixi@gmail.com>,
	Linux Filesystem Development List <linux-fsdevel@vger.kernel.org>,
	ext4 development <linux-ext4@vger.kernel.org>,
	linux-api@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	Dmitry Monakhov <dmonakhov@openvz.org>
Subject: Re: [v8 2/5] ext4: adds project ID support
Date: Fri, 9 Jan 2015 10:47:58 +0100	[thread overview]
Message-ID: <20150109094758.GA2576@quack.suse.cz> (raw)
In-Reply-To: <2EE35986-B398-432E-92D4-EEF875381319@dilger.ca>

On Thu 08-01-15 15:20:21, Andreas Dilger wrote:
> On Jan 8, 2015, at 1:26 AM, Jan Kara <jack@suse.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.
  Agreed. I was somewhat worried about having on-disk flag defined through
the external non-ext4 define but you are right that neither can really
change once we ship a kernel with it.

> 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.
  OK, I've missed that. So if things will be consistent again, I'm fine
with the change.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR