[PATCH 3/5] xfs: simplify tagged perag iteration

[Christoph Hellwig <hch@lst.de>]

Pass the old perag structure to the tagged loop helpers so that they can
grab the old agno before releasing the reference.  This removes the need
to separately track the agno and the iterator macro, and thus also
obsoletes the for_each_perag_tag syntactic sugar.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_icache.c | 69 +++++++++++++++++++++------------------------
 fs/xfs/xfs_trace.h  |  4 +--
 2 files changed, 34 insertions(+), 39 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index ac604640d36229..4d71fbfe71299a 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -296,60 +296,63 @@ xfs_perag_clear_inode_tag(
  * Search from @first to find the next perag with the given tag set.
  */
 static struct xfs_perag *
-xfs_perag_get_tag(
+xfs_perag_get_next_tag(
 	struct xfs_mount	*mp,
-	xfs_agnumber_t		first,
+	struct xfs_perag	*pag,
 	unsigned int		tag)
 {
-	struct xfs_perag	*pag;
+	unsigned long		index = 0;
 	int			found;
 
+	if (pag) {
+		index = pag->pag_agno + 1;
+		xfs_perag_rele(pag);
+	}
+
 	rcu_read_lock();
 	found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
-					(void **)&pag, first, 1, tag);
+					(void **)&pag, index, 1, tag);
 	if (found <= 0) {
 		rcu_read_unlock();
 		return NULL;
 	}
-	trace_xfs_perag_get_tag(pag, _RET_IP_);
+	trace_xfs_perag_get_next_tag(pag, _RET_IP_);
 	atomic_inc(&pag->pag_ref);
 	rcu_read_unlock();
 	return pag;
 }
 
 /*
- * Search from @first to find the next perag with the given tag set.
+ * Find the next AG after @pag, or the first AG if @pag is NULL.
  */
 static struct xfs_perag *
-xfs_perag_grab_tag(
+xfs_perag_grab_next_tag(
 	struct xfs_mount	*mp,
-	xfs_agnumber_t		first,
+	struct xfs_perag	*pag,
 	int			tag)
 {
-	struct xfs_perag	*pag;
+	unsigned long		index = 0;
 	int			found;
 
+	if (pag) {
+		index = pag->pag_agno + 1;
+		xfs_perag_rele(pag);
+	}
+
 	rcu_read_lock();
 	found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
-					(void **)&pag, first, 1, tag);
+					(void **)&pag, index, 1, tag);
 	if (found <= 0) {
 		rcu_read_unlock();
 		return NULL;
 	}
-	trace_xfs_perag_grab_tag(pag, _RET_IP_);
+	trace_xfs_perag_grab_next_tag(pag, _RET_IP_);
 	if (!atomic_inc_not_zero(&pag->pag_active_ref))
 		pag = NULL;
 	rcu_read_unlock();
 	return pag;
 }
 
-#define for_each_perag_tag(mp, agno, pag, tag) \
-	for ((agno) = 0, (pag) = xfs_perag_grab_tag((mp), 0, (tag)); \
-		(pag) != NULL; \
-		(agno) = (pag)->pag_agno + 1, \
-		xfs_perag_rele(pag), \
-		(pag) = xfs_perag_grab_tag((mp), (agno), (tag)))
-
 /*
  * When we recycle a reclaimable inode, we need to re-initialise the VFS inode
  * part of the structure. This is made more complex by the fact we store
@@ -1077,15 +1080,11 @@ long
 xfs_reclaim_inodes_count(
 	struct xfs_mount	*mp)
 {
-	struct xfs_perag	*pag;
-	xfs_agnumber_t		ag = 0;
+	struct xfs_perag	*pag = NULL;
 	long			reclaimable = 0;
 
-	while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
-		ag = pag->pag_agno + 1;
+	while ((pag = xfs_perag_get_next_tag(mp, pag, XFS_ICI_RECLAIM_TAG)))
 		reclaimable += pag->pag_ici_reclaimable;
-		xfs_perag_put(pag);
-	}
 	return reclaimable;
 }
 
@@ -1427,14 +1426,13 @@ void
 xfs_blockgc_start(
 	struct xfs_mount	*mp)
 {
-	struct xfs_perag	*pag;
-	xfs_agnumber_t		agno;
+	struct xfs_perag	*pag = NULL;
 
 	if (xfs_set_blockgc_enabled(mp))
 		return;
 
 	trace_xfs_blockgc_start(mp, __return_address);
-	for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
+	while ((pag = xfs_perag_grab_next_tag(mp, pag, XFS_ICI_BLOCKGC_TAG)))
 		xfs_blockgc_queue(pag);
 }
 
@@ -1550,21 +1548,19 @@ int
 xfs_blockgc_flush_all(
 	struct xfs_mount	*mp)
 {
-	struct xfs_perag	*pag;
-	xfs_agnumber_t		agno;
+	struct xfs_perag	*pag = NULL;
 
 	trace_xfs_blockgc_flush_all(mp, __return_address);
 
 	/*
-	 * For each blockgc worker, move its queue time up to now.  If it
-	 * wasn't queued, it will not be requeued.  Then flush whatever's
-	 * left.
+	 * For each blockgc worker, move its queue time up to now.  If it wasn't
+	 * queued, it will not be requeued.  Then flush whatever is left.
 	 */
-	for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
+	while ((pag = xfs_perag_grab_next_tag(mp, pag, XFS_ICI_BLOCKGC_TAG)))
 		mod_delayed_work(pag->pag_mount->m_blockgc_wq,
 				&pag->pag_blockgc_work, 0);
 
-	for_each_perag_tag(mp, agno, pag, XFS_ICI_BLOCKGC_TAG)
+	while ((pag = xfs_perag_grab_next_tag(mp, pag, XFS_ICI_BLOCKGC_TAG)))
 		flush_delayed_work(&pag->pag_blockgc_work);
 
 	return xfs_inodegc_flush(mp);
@@ -1810,12 +1806,11 @@ xfs_icwalk(
 	enum xfs_icwalk_goal	goal,
 	struct xfs_icwalk	*icw)
 {
-	struct xfs_perag	*pag;
+	struct xfs_perag	*pag = NULL;
 	int			error = 0;
 	int			last_error = 0;
-	xfs_agnumber_t		agno;
 
-	for_each_perag_tag(mp, agno, pag, goal) {
+	while ((pag = xfs_perag_grab_next_tag(mp, pag, goal))) {
 		error = xfs_icwalk_ag(pag, goal, icw);
 		if (error) {
 			last_error = error;
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 180ce697305a92..002d012ebd83cb 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -210,11 +210,11 @@ DEFINE_EVENT(xfs_perag_class, name,	\
 	TP_PROTO(struct xfs_perag *pag, unsigned long caller_ip), \
 	TP_ARGS(pag, caller_ip))
 DEFINE_PERAG_REF_EVENT(xfs_perag_get);
-DEFINE_PERAG_REF_EVENT(xfs_perag_get_tag);
+DEFINE_PERAG_REF_EVENT(xfs_perag_get_next_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_hold);
 DEFINE_PERAG_REF_EVENT(xfs_perag_put);
 DEFINE_PERAG_REF_EVENT(xfs_perag_grab);
-DEFINE_PERAG_REF_EVENT(xfs_perag_grab_tag);
+DEFINE_PERAG_REF_EVENT(xfs_perag_grab_next_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_rele);
 DEFINE_PERAG_REF_EVENT(xfs_perag_set_inode_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_clear_inode_tag);
-- 
2.43.0