linux-kernel - Re: [PATCH] fs: btrfs: Use ktime_get_real

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Date:   Sun, 2 Oct 2016 01:06:04 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Deepa Dinamani <deepa.kernel@...il.com>
Cc:     linux-kernel@...r.kernel.org, arnd@...db.de,
        Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        y2038@...ts.linaro.org, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH] fs: btrfs: Use ktime_get_real_ts for root ctime

On Sat, Oct 01, 2016 at 10:23:34AM -0700, Deepa Dinamani wrote:
> btrfs_root_item maintains the ctime for root updates.
> This is not part of vfs_inode.
> 
> Since current_time() uses struct inode* as an argument
> as Linus suggested, this cannot be used to update root
> times unless, we modify the signature to use inode.
> 
> Since btrfs uses nanosecond time granularity, it can also
> use ktime_get_real_ts directly to obtain timestamp for
> the root. It is necessary to use the timespec time api
> here because the same btrfs_set_stack_timespec_*() apis
> are used for vfs inode times as well. These can be
> transitioned to using timespec64 when btrfs internally
> changes to use timespec64 as well.
> 
> Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
> Cc: Chris Mason <clm@...com>
> Cc: David Sterba <dsterba@...e.com>

Acked-by: David Sterba <dsterba@...e.com>

> Cc: Josef Bacik <jbacik@...com>
> Cc: linux-btrfs@...r.kernel.org
> ---
> Changes from previous version:
> * Separated from the current_time() api series.
> * Moved ktime_get_real_ts() outside of spin lock.
> 
> fs/btrfs/root-tree.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> index 0912960..17e5a5f 100644
> --- a/fs/btrfs/root-tree.c
> +++ b/fs/btrfs/root-tree.c
> @@ -505,8 +505,9 @@ void btrfs_update_root_times(struct btrfs_trans_handle *trans,
>  			     struct btrfs_root *root)
>  {
>  	struct btrfs_root_item *item = &root->root_item;
> -	struct timespec ct = current_fs_time(root->fs_info->sb);
> +	struct timespec ct;
>  
> +	ktime_get_real_ts(&ct);
>  	spin_lock(&root->root_item_lock);
>  	btrfs_set_root_ctransid(item, trans->transid);
>  	btrfs_set_stack_timespec_sec(&item->ctime, ct.tv_sec);
> -- 
> 2.7.4
> 
>