linux-kernel - Re: [RFC PATCH 04/35] ovl: copy up times

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Date:   Fri, 13 Apr 2018 10:23:13 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 04/35] ovl: copy up times

On Thu, Apr 12, 2018 at 05:07:55PM +0200, Miklos Szeredi wrote:
> Copy up mtime and ctime to overlay inode after times in real object are
> modified.  Be careful not to dirty cachelines when not necessary.
> 
> This is in preparation for moving overlay functionality out of the VFS.
> 
> This patch shouldn't have any observable effect.

So there are bunch of operations which will change inode ctime. I had
missed this in my metadata only copy up patch series and that would broken
atime updates in some cases.

Vivek

> 
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
>  fs/overlayfs/dir.c       |  5 +++++
>  fs/overlayfs/inode.c     |  1 +
>  fs/overlayfs/overlayfs.h |  7 +++++++
>  fs/overlayfs/util.c      | 19 +++++++++++++++++++
>  4 files changed, 32 insertions(+)
> 
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index 839709c7803a..cd0fa2363723 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -507,6 +507,7 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
>  		else
>  			err = ovl_create_over_whiteout(dentry, inode, attr,
>  							hardlink);
> +		ovl_copytimes_with_parent(dentry);
>  	}
>  out_revert_creds:
>  	revert_creds(old_cred);
> @@ -768,6 +769,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
>  			drop_nlink(dentry->d_inode);
>  	}
>  	ovl_nlink_end(dentry, locked);
> +	ovl_copytimes_with_parent(dentry);
>  out_drop_write:
>  	ovl_drop_write(dentry);
>  out:
> @@ -1079,6 +1081,9 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
>  	ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old) ||
>  			       (d_inode(new) && ovl_type_origin(new)));
>  
> +	ovl_copytimes_with_parent(old);
> +	ovl_copytimes_with_parent(new);
> +
>  out_dput:
>  	dput(newdentry);
>  out_dput_old:
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 6e3815fb006b..33635106c5f7 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -303,6 +303,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
>  		err = vfs_removexattr(realdentry, name);
>  	}
>  	revert_creds(old_cred);
> +	ovl_copytimes(d_inode(dentry));
>  
>  out_drop_write:
>  	ovl_drop_write(dentry);
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index e0b7de799f6b..eef720ef0f07 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -258,6 +258,13 @@ bool ovl_need_index(struct dentry *dentry);
>  int ovl_nlink_start(struct dentry *dentry, bool *locked);
>  void ovl_nlink_end(struct dentry *dentry, bool locked);
>  int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
> +void ovl_copytimes(struct inode *inode);
> +
> +static inline void ovl_copytimes_with_parent(struct dentry *dentry)
> +{
> +	ovl_copytimes(d_inode(dentry));
> +	ovl_copytimes(d_inode(dentry->d_parent));
> +}
>  
>  static inline bool ovl_is_impuredir(struct dentry *dentry)
>  {
> diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> index 6f1078028c66..11e62e70733a 100644
> --- a/fs/overlayfs/util.c
> +++ b/fs/overlayfs/util.c
> @@ -675,3 +675,22 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
>  	pr_err("overlayfs: failed to lock workdir+upperdir\n");
>  	return -EIO;
>  }
> +
> +void ovl_copytimes(struct inode *inode)
> +{
> +	struct inode *upperinode;
> +
> +	if (!inode)
> +		return;
> +
> +	upperinode = ovl_inode_upper(inode);
> +
> +	if (!upperinode)
> +		return;
> +
> +	if ((!timespec_equal(&inode->i_mtime, &upperinode->i_mtime) ||
> +	     !timespec_equal(&inode->i_ctime, &upperinode->i_ctime))) {
> +		inode->i_mtime = upperinode->i_mtime;
> +		inode->i_ctime = upperinode->i_ctime;
> +	}
> +}
> -- 
> 2.14.3
> 
> --
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