[PATCH 27/37] xfs: convert perag lookup to xarray

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Christoph Hellwig <hch@xxxxxx>

Source kernel commit: 32fa4059fe6776d7db1e9058f360e06b36c9f2ce

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@xxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Chandan Babu R <chandanbabu@xxxxxxxxxx>
---
 include/xfs_mount.h |    2 +-
 libxfs/init.c       |    2 +-
 libxfs/xfs_ag.c     |   31 ++++++++-----------------------
 3 files changed, 10 insertions(+), 25 deletions(-)


diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 7571df12fba3f8..e2add8a648f887 100644
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -91,7 +91,7 @@ typedef struct xfs_mount {
 	xfs_extlen_t		m_ag_prealloc_blocks; /* reserved ag blocks */
 	uint			m_alloc_set_aside; /* space we can't use */
 	uint			m_ag_max_usable; /* max space per AG */
-	struct radix_tree_root	m_perag_tree;
+	struct xarray		m_perags;
 	uint64_t		m_features;	/* active filesystem features */
 	uint64_t		m_low_space[XFS_LOWSP_MAX];
 	uint64_t		m_rtxblkmask;	/* rt extent block mask */
diff --git a/libxfs/init.c b/libxfs/init.c
index 6ab5ef54bb69cb..1e45f091dbb5bf 100644
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -662,7 +662,7 @@ libxfs_mount(
 	mp->m_finobt_nores = true;
 	xfs_set_inode32(mp);
 	mp->m_sb = *sb;
-	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_KERNEL);
+	xa_init(&mp->m_perags);
 	sbp = &mp->m_sb;
 	spin_lock_init(&mp->m_sb_lock);
 	spin_lock_init(&mp->m_agirotor_lock);
diff --git a/libxfs/xfs_ag.c b/libxfs/xfs_ag.c
index a63d9c0dc6fe44..516c76790cc0d8 100644
--- a/libxfs/xfs_ag.c
+++ b/libxfs/xfs_ag.c
@@ -44,7 +44,7 @@ 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);
@@ -90,7 +90,7 @@ 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))
@@ -193,9 +193,7 @@ 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);
@@ -284,9 +282,7 @@ 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);
@@ -327,20 +323,11 @@ 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. */
@@ -388,9 +375,7 @@ 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: