[PATCH] vmalloc: Convert to XArray

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

The radix tree of vmap blocks is simpler to express as an XArray.
Reduces both the text and data sizes of the object file and eliminates
a user of the radix tree preload API.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 mm/vmalloc.c | 40 +++++++++++-----------------------------
 1 file changed, 11 insertions(+), 29 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1e94497b7388..375bbb410a94 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -25,7 +25,7 @@
 #include <linux/list.h>
 #include <linux/notifier.h>
 #include <linux/rbtree.h>
-#include <linux/radix-tree.h>
+#include <linux/xarray.h>
 #include <linux/rcupdate.h>
 #include <linux/pfn.h>
 #include <linux/kmemleak.h>
@@ -1513,12 +1513,11 @@ struct vmap_block {
 static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue);
 
 /*
- * Radix tree of vmap blocks, indexed by address, to quickly find a vmap block
+ * XArray of vmap blocks, indexed by address, to quickly find a vmap block
  * in the free path. Could get rid of this if we change the API to return a
  * "cookie" from alloc, to be passed to free. But no big deal yet.
  */
-static DEFINE_SPINLOCK(vmap_block_tree_lock);
-static RADIX_TREE(vmap_block_tree, GFP_ATOMIC);
+static DEFINE_XARRAY(vmap_blocks);
 
 /*
  * We should probably have a fallback mechanism to allocate virtual memory
@@ -1575,13 +1574,6 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
 		return ERR_CAST(va);
 	}
 
-	err = radix_tree_preload(gfp_mask);
-	if (unlikely(err)) {
-		kfree(vb);
-		free_vmap_area(va);
-		return ERR_PTR(err);
-	}
-
 	vaddr = vmap_block_vaddr(va->va_start, 0);
 	spin_lock_init(&vb->lock);
 	vb->va = va;
@@ -1594,11 +1586,12 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
 	INIT_LIST_HEAD(&vb->free_list);
 
 	vb_idx = addr_to_vb_idx(va->va_start);
-	spin_lock(&vmap_block_tree_lock);
-	err = radix_tree_insert(&vmap_block_tree, vb_idx, vb);
-	spin_unlock(&vmap_block_tree_lock);
-	BUG_ON(err);
-	radix_tree_preload_end();
+	err = xa_insert(&vmap_blocks, vb_idx, vb, gfp_mask);
+	if (err) {
+		kfree(vb);
+		free_vmap_area(va);
+		return ERR_PTR(err);
+	}
 
 	vbq = &get_cpu_var(vmap_block_queue);
 	spin_lock(&vbq->lock);
@@ -1612,12 +1605,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
 static void free_vmap_block(struct vmap_block *vb)
 {
 	struct vmap_block *tmp;
-	unsigned long vb_idx;
 
-	vb_idx = addr_to_vb_idx(vb->va->va_start);
-	spin_lock(&vmap_block_tree_lock);
-	tmp = radix_tree_delete(&vmap_block_tree, vb_idx);
-	spin_unlock(&vmap_block_tree_lock);
+	tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start));
 	BUG_ON(tmp != vb);
 
 	free_vmap_area_noflush(vb->va);
@@ -1723,7 +1712,6 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
 static void vb_free(unsigned long addr, unsigned long size)
 {
 	unsigned long offset;
-	unsigned long vb_idx;
 	unsigned int order;
 	struct vmap_block *vb;
 
@@ -1733,14 +1721,8 @@ static void vb_free(unsigned long addr, unsigned long size)
 	flush_cache_vunmap(addr, addr + size);
 
 	order = get_order(size);
-
 	offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
-
-	vb_idx = addr_to_vb_idx(addr);
-	rcu_read_lock();
-	vb = radix_tree_lookup(&vmap_block_tree, vb_idx);
-	rcu_read_unlock();
-	BUG_ON(!vb);
+	vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr));
 
 	unmap_kernel_range_noflush(addr, size);
 
-- 
2.26.2