linux-kernel - Re: [PATCH 14/19] xfs: convert to new i

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Message-ID: <20171213224837.GB5858@dastard>
Date:   Thu, 14 Dec 2017 09:48:37 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        hch@....de, neilb@...e.de, bfields@...ldses.org,
        amir73il@...il.com, jack@...e.de, viro@...iv.linux.org.uk
Subject: Re: [PATCH 14/19] xfs: convert to new i_version API

On Wed, Dec 13, 2017 at 09:20:12AM -0500, Jeff Layton wrote:
> From: Jeff Layton <jlayton@...hat.com>
> 
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  fs/xfs/libxfs/xfs_inode_buf.c | 5 +++--
>  fs/xfs/xfs_icache.c           | 4 ++--
>  fs/xfs/xfs_inode.c            | 2 +-
>  fs/xfs/xfs_inode_item.c       | 2 +-
>  fs/xfs/xfs_trans_inode.c      | 2 +-
>  5 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index 6b7989038d75..6b47de201391 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -264,7 +264,8 @@ xfs_inode_from_disk(
>  	to->di_flags	= be16_to_cpu(from->di_flags);
>  
>  	if (to->di_version == 3) {
> -		inode->i_version = be64_to_cpu(from->di_changecount);
> +		inode_set_iversion_queried(inode,
> +					   be64_to_cpu(from->di_changecount));

So we use the "kernel managed" (really not sure what that means)
set function here to read it off disk, but...

>  		to->di_crtime.t_sec = be32_to_cpu(from->di_crtime.t_sec);
>  		to->di_crtime.t_nsec = be32_to_cpu(from->di_crtime.t_nsec);
>  		to->di_flags2 = be64_to_cpu(from->di_flags2);
> @@ -314,7 +315,7 @@ xfs_inode_to_disk(
>  	to->di_flags = cpu_to_be16(from->di_flags);
>  
>  	if (from->di_version == 3) {
> -		to->di_changecount = cpu_to_be64(inode->i_version);
> +		to->di_changecount = cpu_to_be64(inode_peek_iversion_raw(inode));

... use the raw access mode to put it back on disk.

>  		to->di_crtime.t_sec = cpu_to_be32(from->di_crtime.t_sec);
>  		to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.t_nsec);
>  		to->di_flags2 = cpu_to_be64(from->di_flags2);
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 43005fbe8b1e..4838462616fd 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -293,14 +293,14 @@ xfs_reinit_inode(
>  	int		error;
>  	uint32_t	nlink = inode->i_nlink;
>  	uint32_t	generation = inode->i_generation;
> -	uint64_t	version = inode->i_version;
> +	uint64_t	version = inode_peek_iversion_raw(inode);
>  	umode_t		mode = inode->i_mode;
>  
>  	error = inode_init_always(mp->m_super, inode);
>  
>  	set_nlink(inode, nlink);
>  	inode->i_generation = generation;
> -	inode->i_version = version;
> +	inode_set_iversion_queried(inode, version);

Again - raw mode to read, kernel managed to set.

>  	inode->i_mode = mode;
>  	return error;
>  }
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 801274126648..be6d87980dd5 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -833,7 +833,7 @@ xfs_ialloc(
>  	ip->i_d.di_flags = 0;
>  
>  	if (ip->i_d.di_version == 3) {
> -		inode->i_version = 1;
> +		inode_set_iversion(inode, 1);

But here you are using the "filesystem managed" mdoe to set the
new value. Why? How is this any different from reading the value
off disk and setting it?

> +++ b/fs/xfs/xfs_trans_inode.c
> @@ -117,7 +117,7 @@ xfs_trans_log_inode(
>  	 */
>  	if (!(ip->i_itemp->ili_item.li_desc->lid_flags & XFS_LID_DIRTY) &&
>  	    IS_I_VERSION(VFS_I(ip))) {
> -		VFS_I(ip)->i_version++;
> +		inode_inc_iversion(VFS_I(ip));
>  		flags |= XFS_ILOG_CORE;
>  	}

And isn't this a case of "filesystem managed" iversion behaviour?

Basically, I can't make head or tail of why the different API
functions are used here....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com