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Date:   Tue, 8 Aug 2023 12:05:57 +0200
From:   Jan Kara <jack@suse.cz>
To:     Jeff Layton <jlayton@kernel.org>
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Subject: Re: [PATCH v7 13/13] btrfs: convert to multigrain timestamps
Message-ID: <20230808100557.dowlxz2destpseqr@quack3>
References: <20230807-mgctime-v7-0-d1dec143a704@kernel.org>
 <20230807-mgctime-v7-13-d1dec143a704@kernel.org>
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In-Reply-To: <20230807-mgctime-v7-13-d1dec143a704@kernel.org>
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On Mon 07-08-23 15:38:44, Jeff Layton wrote:
> Enable multigrain timestamps, which should ensure that there is an
> apparent change to the timestamp whenever it has been written after
> being actively observed via getattr.
> 
> Beyond enabling the FS_MGTIME flag, this patch eliminates
> update_time_for_write, which goes to great pains to avoid in-memory
> stores. Just have it overwrite the timestamps unconditionally.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> Acked-by: David Sterba <dsterba@suse.com>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/btrfs/file.c  | 24 ++++--------------------
>  fs/btrfs/super.c |  5 +++--
>  2 files changed, 7 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index d7a9ece7a40b..b9e75c9f95ac 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1106,25 +1106,6 @@ void btrfs_check_nocow_unlock(struct btrfs_inode *inode)
>  	btrfs_drew_write_unlock(&inode->root->snapshot_lock);
>  }
>  
> -static void update_time_for_write(struct inode *inode)
> -{
> -	struct timespec64 now, ctime;
> -
> -	if (IS_NOCMTIME(inode))
> -		return;
> -
> -	now = current_time(inode);
> -	if (!timespec64_equal(&inode->i_mtime, &now))
> -		inode->i_mtime = now;
> -
> -	ctime = inode_get_ctime(inode);
> -	if (!timespec64_equal(&ctime, &now))
> -		inode_set_ctime_to_ts(inode, now);
> -
> -	if (IS_I_VERSION(inode))
> -		inode_inc_iversion(inode);
> -}
> -
>  static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
>  			     size_t count)
>  {
> @@ -1156,7 +1137,10 @@ static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
>  	 * need to start yet another transaction to update the inode as we will
>  	 * update the inode when we finish writing whatever data we write.
>  	 */
> -	update_time_for_write(inode);
> +	if (!IS_NOCMTIME(inode)) {
> +		inode->i_mtime = inode_set_ctime_current(inode);
> +		inode_inc_iversion(inode);
> +	}
>  
>  	start_pos = round_down(pos, fs_info->sectorsize);
>  	oldsize = i_size_read(inode);
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index f1dd172d8d5b..8eda51b095c9 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2144,7 +2144,7 @@ static struct file_system_type btrfs_fs_type = {
>  	.name		= "btrfs",
>  	.mount		= btrfs_mount,
>  	.kill_sb	= btrfs_kill_super,
> -	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
> +	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_MGTIME,
>  };
>  
>  static struct file_system_type btrfs_root_fs_type = {
> @@ -2152,7 +2152,8 @@ static struct file_system_type btrfs_root_fs_type = {
>  	.name		= "btrfs",
>  	.mount		= btrfs_mount_root,
>  	.kill_sb	= btrfs_kill_super,
> -	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_ALLOW_IDMAP,
> +	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA |
> +			  FS_ALLOW_IDMAP | FS_MGTIME,
>  };
>  
>  MODULE_ALIAS_FS("btrfs");
> 
> -- 
> 2.41.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR