Re: [PATCH] ext4: unconditionally enable the i_version counter

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Jul 25, 2022 at 03:29:46PM -0400, Jeff Layton wrote:
> The original i_version implementation was pretty expensive, requiring a
> log flush on every change. Because of this, it was gated behind a mount
> option (implemented via the MS_I_VERSION mountoption flag).
> 
> Commit ae5e165d855d (fs: new API for handling inode->i_version) made the
> i_version flag much less expensive, so there is no longer a performance
> penalty from enabling it.
> 
> Have ext4 ignore the SB_I_VERSION flag, and just enable it
> unconditionally.
> 
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Lukas Czerner <lczerner@redhat.com>
> Cc: Benjamin Coddington <bcodding@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/ext4/inode.c | 5 ++---
>  fs/ext4/super.c | 8 ++++----
>  2 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 84c0eb55071d..c785c0b72116 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5411,7 +5411,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>  			return -EINVAL;
>  		}
>  
> -		if (IS_I_VERSION(inode) && attr->ia_size != inode->i_size)
> +		if (attr->ia_size != inode->i_size)
>  			inode_inc_iversion(inode);
>  
>  		if (shrink) {
> @@ -5717,8 +5717,7 @@ int ext4_mark_iloc_dirty(handle_t *handle,
>  	}
>  	ext4_fc_track_inode(handle, inode);
>  
> -	if (IS_I_VERSION(inode))
> -		inode_inc_iversion(inode);
> +	inode_inc_iversion(inode);
>  
>  	/* the do_update_inode consumes one bh->b_count */
>  	get_bh(iloc->bh);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 845f2f8aee5f..30645d4343b6 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2142,8 +2142,7 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
>  		return 0;
>  	case Opt_i_version:
>  		ext4_msg(NULL, KERN_WARNING, deprecated_msg, param->key, "5.20");

Perhaps it's time to kill off Opt_i_version, since we're now at 5.20?

(For that matter, noacl/nouser_xattr were supposed to be gone by 3.5 and
they're clearly still there, so either they ought to go as well?)

--D

> -		ext4_msg(NULL, KERN_WARNING, "Use iversion instead\n");
> -		ctx_set_flags(ctx, SB_I_VERSION);
> +		ext4_msg(NULL, KERN_WARNING, "i_version counter is always enabled.\n");
>  		return 0;
>  	case Opt_inlinecrypt:
>  #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
> @@ -2970,8 +2969,6 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
>  		SEQ_OPTS_PRINT("min_batch_time=%u", sbi->s_min_batch_time);
>  	if (nodefs || sbi->s_max_batch_time != EXT4_DEF_MAX_BATCH_TIME)
>  		SEQ_OPTS_PRINT("max_batch_time=%u", sbi->s_max_batch_time);
> -	if (sb->s_flags & SB_I_VERSION)
> -		SEQ_OPTS_PUTS("i_version");
>  	if (nodefs || sbi->s_stripe)
>  		SEQ_OPTS_PRINT("stripe=%lu", sbi->s_stripe);
>  	if (nodefs || EXT4_MOUNT_DATA_FLAGS &
> @@ -4630,6 +4627,9 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>  	sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
>  		(test_opt(sb, POSIX_ACL) ? SB_POSIXACL : 0);
>  
> +	/* i_version is always enabled now */
> +	sb->s_flags |= SB_I_VERSION;
> +
>  	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV &&
>  	    (ext4_has_compat_features(sb) ||
>  	     ext4_has_ro_compat_features(sb) ||
> -- 
> 2.37.1
>