[PATCH] btrfs: extent_io: Handle memory allocation failure in __clear_extent_bit()

[Qu Wenruo <wqu@suse.com>]

There is a BUG_ON() in __clear_extent_bit() for memory allocation
failure.

While comment of __clear_extent_bit() says it can return error, but we
always return 0.

Some __clear_extent_bit() callers just ignore the return value, while
some still expect error.

Let's return proper error for this memory allocation anyway, to remove
that BUG_ON() as a first step, so at least we can continue test.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent_io.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 828708f6510c..f1bfc632ef7b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -743,7 +743,10 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 
 	if (state->start < start) {
 		prealloc = alloc_extent_state_atomic(prealloc);
-		BUG_ON(!prealloc);
+		if (!prealloc) {
+			err = -ENOMEM;
+			goto out;
+		}
 		err = split_state(tree, state, prealloc, start);
 		if (err)
 			extent_io_tree_panic(tree, err);
@@ -766,7 +769,10 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 	 */
 	if (state->start <= end && state->end > end) {
 		prealloc = alloc_extent_state_atomic(prealloc);
-		BUG_ON(!prealloc);
+		if (!prealloc) {
+			err = -ENOMEM;
+			goto out;
+		}
 		err = split_state(tree, state, prealloc, end + 1);
 		if (err)
 			extent_io_tree_panic(tree, err);
@@ -801,6 +807,8 @@ int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 	if (prealloc)
 		free_extent_state(prealloc);
 
+	if (err)
+		return err;
 	return 0;
 
 }
-- 
2.21.0