Re: [PATCH 2/2] xfs: reduce ilock acquisitions in xfs_file_fsync

[Brian Foster <bfoster@redhat.com>]

On Fri, Jan 22, 2021 at 05:46:43PM +0100, Christoph Hellwig wrote:
> If the inode is not pinned by the time fsync is called we don't need the
> ilock to protect against concurrent clearing of ili_fsync_fields as the
> inode won't need a log flush or clearing of these fields.  Not taking
> the iolock allows for full concurrency of fsync and thus O_DSYNC
> completions with io_uring/aio write submissions.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_file.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 588232c77f11e0..ffe2d7c37e26cd 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -200,7 +200,14 @@ xfs_file_fsync(
>  	else if (mp->m_logdev_targp != mp->m_ddev_targp)
>  		xfs_blkdev_issue_flush(mp->m_ddev_targp);
>  
> -	error = xfs_fsync_flush_log(ip, datasync, &log_flushed);
> +	/*
> +	 * Any inode that has dirty modifications in the log is pinned.  The
> +	 * racy check here for a pinned inode while not catch modifications

s/while/will/ ?

Otherwise looks good:

Reviewed-by: Brian Foster <bfoster@redhat.com>

> +	 * that happen concurrently to the fsync call, but fsync semantics
> +	 * only require to sync previously completed I/O.
> +	 */
> +	if (xfs_ipincount(ip))
> +		error = xfs_fsync_flush_log(ip, datasync, &log_flushed);
>  
>  	/*
>  	 * If we only have a single device, and the log force about was
> -- 
> 2.29.2
>