[PATCH 37/62] shmem: Convert replace to xarray

Matthew Wilcox
2017-11-22T21:14:32Z

shmem_radix_tree_replace() is renamed to shmem_xa_replace() and
converted to use the XArray API.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
mm/shmem.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 21bf42f14ee2..f16afa03cfb0 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -321,24 +321,20 @@ void shmem_uncharge(struct inode *inode, long pages)
}

/*
- * Replace item expected in radix tree by a new item, while holding tree lock.
+ * Replace item expected in xarray by a new item, while holding xa_lock.
*/
-static int shmem_radix_tree_replace(struct address_space *mapping,
+static int shmem_xa_replace(struct address_space *mapping,
pgoff_t index, void *expected, void *replacement)
{
- struct radix_tree_node *node;
- void **pslot;
+ XA_STATE(xas, index);
void *item;

VM_BUG_ON(!expected);
VM_BUG_ON(!replacement);
- item = __radix_tree_lookup(&mapping->pages, index, &node, &pslot);
- if (!item)
- return -ENOENT;
+ item = xas_load(&mapping->pages, &xas);
if (item != expected)
return -ENOENT;
- __radix_tree_replace(&mapping->pages, node, pslot,
- replacement, NULL);
+ xas_store(&mapping->pages, &xas, replacement);
return 0;
}

@@ -605,8 +601,7 @@ static int shmem_add_to_page_cache(struct page *page,
} else if (!expected) {
error = radix_tree_insert(&mapping->pages, index, page);
} else {
- error = shmem_radix_tree_replace(mapping, index, expected,
- page);
+ error = shmem_xa_replace(mapping, index, expected, page);
}

if (!error) {
@@ -635,7 +630,7 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
VM_BUG_ON_PAGE(PageCompound(page), page);

xa_lock_irq(&mapping->pages);
- error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
+ error = shmem_xa_replace(mapping, page->index, page, radswap);
page->mapping = NULL;
mapping->nrpages--;
__dec_node_page_state(page, NR_FILE_PAGES);
@@ -1550,8 +1545,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
* a nice clean interface for us to replace oldpage by newpage there.
*/
xa_lock_irq(&swap_mapping->pages);
- error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
- newpage);
+ error = shmem_xa_replace(swap_mapping, swap_index, oldpage, newpage);
if (!error) {
__inc_node_page_state(newpage, NR_FILE_PAGES);
__dec_node_page_state(oldpage, NR_FILE_PAGES);
--
2.15.0