[PATCH 3/4] brd: only preload radix tree if we're using a blocking gfp mask

[Jens Axboe <axboe@kernel.dk>]

radix_tree_preload() warns on attempting to call it with an allocation
mask that doesn't allow blocking. While that warning could arguably
be removed, we need to handle radix insertion failures anyway as they
are more likely if we cannot block to get memory.

Remove legacy BUG_ON()'s and turn them into proper errors instead, one
for the allocation failure and one for finding a page that doesn't
match the correct index.

Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 drivers/block/brd.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 1ddada0cdaca..6019ef23344f 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -84,6 +84,7 @@ static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
 {
 	pgoff_t idx;
 	struct page *page;
+	int ret = 0;
 
 	page = brd_lookup_page(brd, sector);
 	if (page)
@@ -93,7 +94,7 @@ static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
 	if (!page)
 		return -ENOMEM;
 
-	if (radix_tree_preload(gfp)) {
+	if (gfpflags_allow_blocking(gfp) && radix_tree_preload(gfp)) {
 		__free_page(page);
 		return -ENOMEM;
 	}
@@ -104,8 +105,10 @@ static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
 	if (radix_tree_insert(&brd->brd_pages, idx, page)) {
 		__free_page(page);
 		page = radix_tree_lookup(&brd->brd_pages, idx);
-		BUG_ON(!page);
-		BUG_ON(page->index != idx);
+		if (!page)
+			ret = -ENOMEM;
+		else if (page->index != idx)
+			ret = -EIO;
 	} else {
 		brd->brd_nr_pages++;
 	}
-- 
2.39.1