[patch 121/163] vmalloc: convert to XArray

Andrew Morton
2020-08-07T06:24:09Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: vmalloc: convert to XArray

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.

Link: http://lkml.kernel.org/r/20200603171448.5894-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/vmalloc.c | 40 +++++++++++-----------------------------
1 file changed, 11 insertions(+), 29 deletions(-)

--- a/mm/vmalloc.c~vmalloc-convert-to-xarray
+++ a/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>
@@ -1514,12 +1514,11 @@ 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
@@ -1576,13 +1575,6 @@ static void *new_vmap_block(unsigned int
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;
@@ -1595,11 +1587,12 @@ static void *new_vmap_block(unsigned int
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);
@@ -1613,12 +1606,8 @@ static void *new_vmap_block(unsigned int
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);
@@ -1724,7 +1713,6 @@ static void *vb_alloc(unsigned long size
static void vb_free(unsigned long addr, unsigned long size)
{
unsigned long offset;
- unsigned long vb_idx;
unsigned int order;
struct vmap_block *vb;

@@ -1734,14 +1722,8 @@ static void vb_free(unsigned long addr,
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);

_