Re: [PATCH 2/2] xfs: set WQ_SYSFS on all workqueues in debug mode

[Christoph Hellwig <hch@infradead.org>]

On Wed, Jan 27, 2021 at 10:03:36PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> When CONFIG_XFS_DEBUG=y, set WQ_SYSFS on all workqueues that we create
> so that we (developers) have a means to monitor cpu affinity and whatnot
> for background workers.  In the next patchset we'll expose knobs for
> some of the workqueues publicly and document it, but not now.

And I still think this is a horrible idea.

> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_log.c       |    5 +++--
>  fs/xfs/xfs_mru_cache.c |    2 +-
>  fs/xfs/xfs_super.c     |   23 ++++++++++++++---------
>  fs/xfs/xfs_super.h     |    6 ++++++
>  4 files changed, 24 insertions(+), 12 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index d8b814227734..9aa30e7cd314 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1492,8 +1492,9 @@ xlog_alloc_log(
>  	log->l_iclog->ic_prev = prev_iclog;	/* re-write 1st prev ptr */
>  
>  	log->l_ioend_workqueue = alloc_workqueue("xfs-log/%s",
> -			WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_HIGHPRI, 0,
> -			mp->m_super->s_id);
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM |
> +				    WQ_HIGHPRI),
> +			0, mp->m_super->s_id);
>  	if (!log->l_ioend_workqueue)
>  		goto out_free_iclog;
>  
> diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
> index a06661dac5be..34c3b16f834f 100644
> --- a/fs/xfs/xfs_mru_cache.c
> +++ b/fs/xfs/xfs_mru_cache.c
> @@ -294,7 +294,7 @@ int
>  xfs_mru_cache_init(void)
>  {
>  	xfs_mru_reap_wq = alloc_workqueue("xfs_mru_cache",
> -				WQ_MEM_RECLAIM|WQ_FREEZABLE, 1);
> +			XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 1);
>  	if (!xfs_mru_reap_wq)
>  		return -ENOMEM;
>  	return 0;
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index aed74a3fc787..8959561351ca 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -495,33 +495,37 @@ xfs_init_mount_workqueues(
>  	struct xfs_mount	*mp)
>  {
>  	mp->m_buf_workqueue = alloc_workqueue("xfs-buf/%s",
> -			WQ_MEM_RECLAIM|WQ_FREEZABLE, 1, mp->m_super->s_id);
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
> +			1, mp->m_super->s_id);
>  	if (!mp->m_buf_workqueue)
>  		goto out;
>  
>  	mp->m_unwritten_workqueue = alloc_workqueue("xfs-conv/%s",
> -			WQ_MEM_RECLAIM|WQ_FREEZABLE, 0, mp->m_super->s_id);
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
> +			0, mp->m_super->s_id);
>  	if (!mp->m_unwritten_workqueue)
>  		goto out_destroy_buf;
>  
>  	mp->m_cil_workqueue = alloc_workqueue("xfs-cil/%s",
> -			WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND,
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_UNBOUND),
>  			0, mp->m_super->s_id);
>  	if (!mp->m_cil_workqueue)
>  		goto out_destroy_unwritten;
>  
>  	mp->m_reclaim_workqueue = alloc_workqueue("xfs-reclaim/%s",
> -			WQ_MEM_RECLAIM|WQ_FREEZABLE, 0, mp->m_super->s_id);
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
> +			0, mp->m_super->s_id);
>  	if (!mp->m_reclaim_workqueue)
>  		goto out_destroy_cil;
>  
>  	mp->m_eofblocks_workqueue = alloc_workqueue("xfs-eofblocks/%s",
> -			WQ_MEM_RECLAIM|WQ_FREEZABLE, 0, mp->m_super->s_id);
> +			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
> +			0, mp->m_super->s_id);
>  	if (!mp->m_eofblocks_workqueue)
>  		goto out_destroy_reclaim;
>  
> -	mp->m_sync_workqueue = alloc_workqueue("xfs-sync/%s", WQ_FREEZABLE, 0,
> -					       mp->m_super->s_id);
> +	mp->m_sync_workqueue = alloc_workqueue("xfs-sync/%s",
> +			XFS_WQFLAGS(WQ_FREEZABLE), 0, mp->m_super->s_id);
>  	if (!mp->m_sync_workqueue)
>  		goto out_destroy_eofb;
>  
> @@ -2085,11 +2089,12 @@ xfs_init_workqueues(void)
>  	 * max_active value for this workqueue.
>  	 */
>  	xfs_alloc_wq = alloc_workqueue("xfsalloc",
> -			WQ_MEM_RECLAIM|WQ_FREEZABLE, 0);
> +			XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 0);
>  	if (!xfs_alloc_wq)
>  		return -ENOMEM;
>  
> -	xfs_discard_wq = alloc_workqueue("xfsdiscard", WQ_UNBOUND, 0);
> +	xfs_discard_wq = alloc_workqueue("xfsdiscard", XFS_WQFLAGS(WQ_UNBOUND),
> +			0);
>  	if (!xfs_discard_wq)
>  		goto out_free_alloc_wq;
>  
> diff --git a/fs/xfs/xfs_super.h b/fs/xfs/xfs_super.h
> index b552cf6d3379..1ca484b8357f 100644
> --- a/fs/xfs/xfs_super.h
> +++ b/fs/xfs/xfs_super.h
> @@ -75,6 +75,12 @@ extern void xfs_qm_exit(void);
>  				XFS_ASSERT_FATAL_STRING \
>  				XFS_DBG_STRING /* DBG must be last */
>  
> +#ifdef DEBUG
> +# define XFS_WQFLAGS(wqflags)	(WQ_SYSFS | (wqflags))
> +#else
> +# define XFS_WQFLAGS(wqflags)	(wqflags)
> +#endif
> +
>  struct xfs_inode;
>  struct xfs_mount;
>  struct xfs_buftarg;
> 
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