Re: [PATCH 04/22] xfs: make for_each_perag... a first class citizen

[Brian Foster <bfoster@redhat.com>]

On Thu, May 06, 2021 at 05:20:36PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> for_each_perag_tag() is defined in xfs_icache.c for local use.
> Promote this to xfs_ag.h and define equivalent iteration functions
> so that we can use them to iterate AGs instead to replace open coded
> perag walks and perag lookups.
> 
> We also convert as many of the straight forward open coded AG walks
> to use these iterators as possible. Anything that is not a direct
> conversion to an iterator is ignored and will be updated in future
> commits.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_ag.h    | 17 +++++++++++++++++
>  fs/xfs/scrub/fscounters.c | 36 ++++++++++++++----------------------
>  fs/xfs/xfs_extent_busy.c  |  7 ++-----
>  fs/xfs/xfs_fsops.c        |  8 ++------
>  fs/xfs/xfs_health.c       |  4 +---
>  fs/xfs/xfs_icache.c       | 15 ++-------------
>  6 files changed, 38 insertions(+), 49 deletions(-)
> 
...
> diff --git a/fs/xfs/scrub/fscounters.c b/fs/xfs/scrub/fscounters.c
> index 453ae9adf94c..2dfdac566399 100644
> --- a/fs/xfs/scrub/fscounters.c
> +++ b/fs/xfs/scrub/fscounters.c
...
> @@ -229,12 +224,9 @@ xchk_fscount_aggregate_agcounts(
>  		fsc->fdblocks -= pag->pag_meta_resv.ar_reserved;
>  		fsc->fdblocks -= pag->pag_rmapbt_resv.ar_orig_reserved;
>  
> -		xfs_perag_put(pag);
> -
> -		if (xchk_should_terminate(sc, &error))
> -			break;
>  	}
> -
> +	if (pag)
> +		xfs_perag_put(pag);

It's not shown in the diff, but there is still an exit path out of the
above loop that calls xfs_perag_put(). The rest of the patch LGTM.

Brian

>  	if (error)
>  		return error;
>  
> diff --git a/fs/xfs/xfs_extent_busy.c b/fs/xfs/xfs_extent_busy.c
> index 184732aa8674..6af0b5a1c7b0 100644
> --- a/fs/xfs/xfs_extent_busy.c
> +++ b/fs/xfs/xfs_extent_busy.c
> @@ -605,12 +605,11 @@ void
>  xfs_extent_busy_wait_all(
>  	struct xfs_mount	*mp)
>  {
> +	struct xfs_perag	*pag;
>  	DEFINE_WAIT		(wait);
>  	xfs_agnumber_t		agno;
>  
> -	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> -		struct xfs_perag *pag = xfs_perag_get(mp, agno);
> -
> +	for_each_perag(mp, agno, pag) {
>  		do {
>  			prepare_to_wait(&pag->pagb_wait, &wait, TASK_KILLABLE);
>  			if  (RB_EMPTY_ROOT(&pag->pagb_tree))
> @@ -618,8 +617,6 @@ xfs_extent_busy_wait_all(
>  			schedule();
>  		} while (1);
>  		finish_wait(&pag->pagb_wait, &wait);
> -
> -		xfs_perag_put(pag);
>  	}
>  }
>  
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index be9cf88d2ad7..07c745cd483e 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -576,10 +576,8 @@ xfs_fs_reserve_ag_blocks(
>  	int			err2;
>  
>  	mp->m_finobt_nores = false;
> -	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> -		pag = xfs_perag_get(mp, agno);
> +	for_each_perag(mp, agno, pag) {
>  		err2 = xfs_ag_resv_init(pag, NULL);
> -		xfs_perag_put(pag);
>  		if (err2 && !error)
>  			error = err2;
>  	}
> @@ -605,10 +603,8 @@ xfs_fs_unreserve_ag_blocks(
>  	int			error = 0;
>  	int			err2;
>  
> -	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> -		pag = xfs_perag_get(mp, agno);
> +	for_each_perag(mp, agno, pag) {
>  		err2 = xfs_ag_resv_free(pag);
> -		xfs_perag_put(pag);
>  		if (err2 && !error)
>  			error = err2;
>  	}
> diff --git a/fs/xfs/xfs_health.c b/fs/xfs/xfs_health.c
> index b79475ea3dbd..5de3195f6cb2 100644
> --- a/fs/xfs/xfs_health.c
> +++ b/fs/xfs/xfs_health.c
> @@ -34,14 +34,12 @@ xfs_health_unmount(
>  		return;
>  
>  	/* Measure AG corruption levels. */
> -	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> -		pag = xfs_perag_get(mp, agno);
> +	for_each_perag(mp, agno, pag) {
>  		xfs_ag_measure_sickness(pag, &sick, &checked);
>  		if (sick) {
>  			trace_xfs_ag_unfixed_corruption(mp, agno, sick);
>  			warn = true;
>  		}
> -		xfs_perag_put(pag);
>  	}
>  
>  	/* Measure realtime volume corruption levels. */
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 588ea2bf88bb..7dad83a6f586 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -1061,15 +1061,13 @@ xfs_reclaim_inodes_ag(
>  	int			*nr_to_scan)
>  {
>  	struct xfs_perag	*pag;
> -	xfs_agnumber_t		ag = 0;
> +	xfs_agnumber_t		agno;
>  
> -	while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
> +	for_each_perag_tag(mp, agno, pag, XFS_ICI_RECLAIM_TAG) {
>  		unsigned long	first_index = 0;
>  		int		done = 0;
>  		int		nr_found = 0;
>  
> -		ag = pag->pag_agno + 1;
> -
>  		first_index = READ_ONCE(pag->pag_ici_reclaim_cursor);
>  		do {
>  			struct xfs_inode *batch[XFS_LOOKUP_BATCH];
> @@ -1134,7 +1132,6 @@ xfs_reclaim_inodes_ag(
>  		if (done)
>  			first_index = 0;
>  		WRITE_ONCE(pag->pag_ici_reclaim_cursor, first_index);
> -		xfs_perag_put(pag);
>  	}
>  }
>  
> @@ -1554,14 +1551,6 @@ xfs_inode_clear_cowblocks_tag(
>  	return xfs_blockgc_clear_iflag(ip, XFS_ICOWBLOCKS);
>  }
>  
> -#define for_each_perag_tag(mp, next_agno, pag, tag) \
> -	for ((next_agno) = 0, (pag) = xfs_perag_get_tag((mp), 0, (tag)); \
> -		(pag) != NULL; \
> -		(next_agno) = (pag)->pag_agno + 1, \
> -		xfs_perag_put(pag), \
> -		(pag) = xfs_perag_get_tag((mp), (next_agno), (tag)))
> -
> -
>  /* Disable post-EOF and CoW block auto-reclamation. */
>  void
>  xfs_blockgc_stop(
> -- 
> 2.31.1
>