[PATCH] brd: Remove use of page->index

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

This debugging check will become more costly in the future when we shrink
struct page.  It has not proven to be useful, so simply remove it.

This lets us use __xa_insert instead of __xa_cmpxchg() as we no longer
need to know about the page that is currently stored in the XArray.

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

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index e322cef6596b..b900fe9e0030 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -29,10 +29,7 @@
 
 /*
  * Each block ramdisk device has a xarray brd_pages of pages that stores
- * the pages containing the block device's contents. A brd page's ->index is
- * its offset in PAGE_SIZE units. This is similar to, but in no way connected
- * with, the kernel's pagecache or buffer cache (which sit above our block
- * device).
+ * the pages containing the block device's contents.
  */
 struct brd_device {
 	int			brd_number;
@@ -51,15 +48,7 @@ struct brd_device {
  */
 static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
 {
-	pgoff_t idx;
-	struct page *page;
-
-	idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
-	page = xa_load(&brd->brd_pages, idx);
-
-	BUG_ON(page && page->index != idx);
-
-	return page;
+	return xa_load(&brd->brd_pages, sector >> PAGE_SECTORS_SHIFT);
 }
 
 /*
@@ -67,8 +56,8 @@ static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
  */
 static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
 {
-	pgoff_t idx;
-	struct page *page, *cur;
+	pgoff_t idx = sector >> PAGE_SECTORS_SHIFT;
+	struct page *page;
 	int ret = 0;
 
 	page = brd_lookup_page(brd, sector);
@@ -80,23 +69,16 @@ static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
 		return -ENOMEM;
 
 	xa_lock(&brd->brd_pages);
-
-	idx = sector >> PAGE_SECTORS_SHIFT;
-	page->index = idx;
-
-	cur = __xa_cmpxchg(&brd->brd_pages, idx, NULL, page, gfp);
-
-	if (unlikely(cur)) {
-		__free_page(page);
-		ret = xa_err(cur);
-		if (!ret && (cur->index != idx))
-			ret = -EIO;
-	} else {
+	ret = __xa_insert(&brd->brd_pages, idx, page, gfp);
+	if (!ret)
 		brd->brd_nr_pages++;
-	}
-
 	xa_unlock(&brd->brd_pages);
 
+	if (ret < 0) {
+		__free_page(page);
+		if (ret == -EBUSY)
+			ret = 0;
+	}
 	return ret;
 }
 
-- 
2.43.0