xfs: convert perag lookup to xarray

Convert the perag lookup from the legacy radix tree to the xarray,
which allows for much nicer iteration and bulk lookup semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Author: Christoph Hellwig

fs/xfs/libxfs/xfs_ag.c

@@ -46,7 +46,7 @@ xfs_perag_get(
 	struct xfs_perag	*pag;
 
 	rcu_read_lock();
-	pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+	pag = xa_load(&mp->m_perags, agno);
 	if (pag) {
 		trace_xfs_perag_get(pag, _RET_IP_);
 		ASSERT(atomic_read(&pag->pag_ref) >= 0);
@@ -92,7 +92,7 @@ xfs_perag_grab(
 	struct xfs_perag	*pag;
 
 	rcu_read_lock();
-	pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+	pag = xa_load(&mp->m_perags, agno);
 	if (pag) {
 		trace_xfs_perag_grab(pag, _RET_IP_);
 		if (!atomic_inc_not_zero(&pag->pag_active_ref))
@@ -195,9 +195,7 @@ xfs_free_perag(
 	xfs_agnumber_t		agno;
 
 	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
-		spin_lock(&mp->m_perag_lock);
-		pag = radix_tree_delete(&mp->m_perag_tree, agno);
-		spin_unlock(&mp->m_perag_lock);
+		pag = xa_erase(&mp->m_perags, agno);
 		ASSERT(pag);
 		XFS_IS_CORRUPT(pag->pag_mount, atomic_read(&pag->pag_ref) != 0);
 		xfs_defer_drain_free(&pag->pag_intents_drain);
@@ -286,9 +284,7 @@ xfs_free_unused_perag_range(
 	xfs_agnumber_t		index;
 
 	for (index = agstart; index < agend; index++) {
-		spin_lock(&mp->m_perag_lock);
-		pag = radix_tree_delete(&mp->m_perag_tree, index);
-		spin_unlock(&mp->m_perag_lock);
+		pag = xa_erase(&mp->m_perags, index);
 		if (!pag)
 			break;
 		xfs_buf_cache_destroy(&pag->pag_bcache);
@@ -329,20 +325,11 @@ xfs_initialize_perag(
 		pag->pag_agno = index;
 		pag->pag_mount = mp;
 
-		error = radix_tree_preload(GFP_KERNEL | __GFP_RETRY_MAYFAIL);
-		if (error)
-			goto out_free_pag;
-
-		spin_lock(&mp->m_perag_lock);
-		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
-			WARN_ON_ONCE(1);
-			spin_unlock(&mp->m_perag_lock);
-			radix_tree_preload_end();
-			error = -EEXIST;
+		error = xa_insert(&mp->m_perags, index, pag, GFP_KERNEL);
+		if (error) {
+			WARN_ON_ONCE(error == -EBUSY);
 			goto out_free_pag;
 		}
-		spin_unlock(&mp->m_perag_lock);
-		radix_tree_preload_end();
 
 #ifdef __KERNEL__
 		/* Place kernel structure only init below this point. */
@@ -390,9 +377,7 @@ xfs_initialize_perag(
 
 out_remove_pag:
 	xfs_defer_drain_free(&pag->pag_intents_drain);
-	spin_lock(&mp->m_perag_lock);
-	radix_tree_delete(&mp->m_perag_tree, index);
-	spin_unlock(&mp->m_perag_lock);
+	pag = xa_erase(&mp->m_perags, index);
 out_free_pag:
 	kfree(pag);
 out_unwind_new_pags:

fs/xfs/xfs_icache.c

@@ -65,6 +65,18 @@ static int xfs_icwalk_ag(struct xfs_perag *pag,
 					 XFS_ICWALK_FLAG_RECLAIM_SICK | \
 					 XFS_ICWALK_FLAG_UNION)
 
+/* Marks for the perag xarray */
+#define XFS_PERAG_RECLAIM_MARK	XA_MARK_0
+#define XFS_PERAG_BLOCKGC_MARK	XA_MARK_1
+
+static inline xa_mark_t ici_tag_to_mark(unsigned int tag)
+{
+	if (tag == XFS_ICI_RECLAIM_TAG)
+		return XFS_PERAG_RECLAIM_MARK;
+	ASSERT(tag == XFS_ICI_BLOCKGC_TAG);
+	return XFS_PERAG_BLOCKGC_MARK;
+}
+
 /*
  * Allocate and initialise an xfs_inode.
  */
@@ -191,7 +203,7 @@ xfs_reclaim_work_queue(
 {
 
 	rcu_read_lock();
-	if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
+	if (xa_marked(&mp->m_perags, XFS_PERAG_RECLAIM_MARK)) {
 		queue_delayed_work(mp->m_reclaim_workqueue, &mp->m_reclaim_work,
 			msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
 	}
@@ -241,9 +253,7 @@ xfs_perag_set_inode_tag(
 		return;
 
 	/* propagate the tag up into the perag radix tree */
-	spin_lock(&mp->m_perag_lock);
-	radix_tree_tag_set(&mp->m_perag_tree, pag->pag_agno, tag);
-	spin_unlock(&mp->m_perag_lock);
+	xa_set_mark(&mp->m_perags, pag->pag_agno, ici_tag_to_mark(tag));
 
 	/* start background work */
 	switch (tag) {
@@ -285,9 +295,7 @@ xfs_perag_clear_inode_tag(
 		return;
 
 	/* clear the tag from the perag radix tree */
-	spin_lock(&mp->m_perag_lock);
-	radix_tree_tag_clear(&mp->m_perag_tree, pag->pag_agno, tag);
-	spin_unlock(&mp->m_perag_lock);
+	xa_clear_mark(&mp->m_perags, pag->pag_agno, ici_tag_to_mark(tag));
 
 	trace_xfs_perag_clear_inode_tag(pag, _RET_IP_);
 }
@@ -302,22 +310,18 @@ xfs_perag_get_next_tag(
 	unsigned int		tag)
 {
 	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, index, 1, tag);
-	if (found <= 0) {
-		rcu_read_unlock();
-		return NULL;
+	pag = xa_find(&mp->m_perags, &index, ULONG_MAX, ici_tag_to_mark(tag));
+	if (pag) {
+		trace_xfs_perag_get_next_tag(pag, _RET_IP_);
+		atomic_inc(&pag->pag_ref);
 	}
-	trace_xfs_perag_get_next_tag(pag, _RET_IP_);
-	atomic_inc(&pag->pag_ref);
 	rcu_read_unlock();
 	return pag;
 }
@@ -332,23 +336,19 @@ xfs_perag_grab_next_tag(
 	int			tag)
 {
 	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, index, 1, tag);
-	if (found <= 0) {
-		rcu_read_unlock();
-		return NULL;
+	pag = xa_find(&mp->m_perags, &index, ULONG_MAX, ici_tag_to_mark(tag));
+	if (pag) {
+		trace_xfs_perag_grab_next_tag(pag, _RET_IP_);
+		if (!atomic_inc_not_zero(&pag->pag_active_ref))
+			pag = NULL;
 	}
-	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;
 }
@@ -1038,7 +1038,7 @@ xfs_reclaim_inodes(
 	if (xfs_want_reclaim_sick(mp))
 		icw.icw_flags |= XFS_ICWALK_FLAG_RECLAIM_SICK;
 
-	while (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
+	while (xa_marked(&mp->m_perags, XFS_PERAG_RECLAIM_MARK)) {
 		xfs_ail_push_all_sync(mp->m_ail);
 		xfs_icwalk(mp, XFS_ICWALK_RECLAIM, &icw);
 	}

fs/xfs/xfs_mount.h

@@ -208,8 +208,7 @@ typedef struct xfs_mount {
 	 */
 	atomic64_t		m_allocbt_blks;
 
-	struct radix_tree_root	m_perag_tree;	/* per-ag accounting info */
-	spinlock_t		m_perag_lock;	/* lock for m_perag_tree */
+	struct xarray		m_perags;	/* per-ag accounting info */
 	uint64_t		m_resblks;	/* total reserved blocks */
 	uint64_t		m_resblks_avail;/* available reserved blocks */
 	uint64_t		m_resblks_save;	/* reserved blks @ remount,ro */

fs/xfs/xfs_super.c

@@ -2009,8 +2009,7 @@ static int xfs_init_fs_context(
 		return -ENOMEM;
 
 	spin_lock_init(&mp->m_sb_lock);
-	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
-	spin_lock_init(&mp->m_perag_lock);
+	xa_init(&mp->m_perags);
 	mutex_init(&mp->m_growlock);
 	INIT_WORK(&mp->m_flush_inodes_work, xfs_flush_inodes_worker);
 	INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);