Re: [PATCH 07/10] fs: add a ->sync_lazytime method

[Jan Kara <jack@suse.cz>]

On Wed 17-12-25 07:09:40, Christoph Hellwig wrote:
> Allow the file system to explicitly implement lazytime syncing instead
> of pigging back on generic inode dirtying.  This allows to simplify
> the XFS implementation and prepares for non-blocking lazytime timestamp
> updates.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jeff Layton <jlayton@kernel.org>

...

>  	if (flags & I_DIRTY_INODE) {
> +		bool was_dirty_time =
> +			inode_state_read_once(inode) & I_DIRTY_TIME;
> +
>  		/*
>  		 * Inode timestamp update will piggback on this dirtying.
>  		 * We tell ->dirty_inode callback that timestamps need to
>  		 * be updated by setting I_DIRTY_TIME in flags.
>  		 */
> -		if (inode_state_read_once(inode) & I_DIRTY_TIME) {
> +		if (was_dirty_time) {
>  			spin_lock(&inode->i_lock);
>  			if (inode_state_read(inode) & I_DIRTY_TIME) {
>  				inode_state_clear(inode, I_DIRTY_TIME);
>  				flags |= I_DIRTY_TIME;
> +				was_dirty_time = true;

This looks bogus. was_dirty_time is already true here. What I think you
wanted here is to set it to false if locked I_DIRTY_TIME check failed.
Otherwise the patch looks good.

								Honza

>  			}
>  			spin_unlock(&inode->i_lock);
>  		}
> @@ -2591,9 +2598,12 @@ void __mark_inode_dirty(struct inode *inode, int flags)
>  		 * for just I_DIRTY_PAGES or I_DIRTY_TIME.
>  		 */
>  		trace_writeback_dirty_inode_start(inode, flags);
> -		if (sb->s_op->dirty_inode)
> +		if (sb->s_op->dirty_inode) {
>  			sb->s_op->dirty_inode(inode,
>  				flags & (I_DIRTY_INODE | I_DIRTY_TIME));
> +		} else if (was_dirty_time && inode->i_op->sync_lazytime) {
> +			inode->i_op->sync_lazytime(inode);
> +		}
>  		trace_writeback_dirty_inode(inode, flags);
>  
>  		/* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 75d5f38b08c9..255eb3b42d1d 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2011,6 +2011,7 @@ struct inode_operations {
>  	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
>  		      u64 len);
>  	int (*update_time)(struct inode *, int);
> +	void (*sync_lazytime)(struct inode *inode);
>  	int (*atomic_open)(struct inode *, struct dentry *,
>  			   struct file *, unsigned open_flag,
>  			   umode_t create_mode);
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR