From fbf48bb0b197e6894a04c714728c952af7153bf3 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Wed, 3 Mar 2021 18:41:51 +0800
Patch-mainline: v5.12-rc4
Git-commit: fbf48bb0b197e6894a04c714728c952af7153bf3
References: bsc#1185549
Subject: [PATCH 1/2] btrfs: track qgroup released data in own variable in
 insert_prealloc_file_extent

There is a piece of weird code in insert_prealloc_file_extent(), which
looks like:

	ret = btrfs_qgroup_release_data(inode, file_offset, len);
	if (ret < 0)
		return ERR_PTR(ret);
	if (trans) {
		ret = insert_reserved_file_extent(trans, inode,
						  file_offset, &stack_fi,
						  true, ret);
	...
	}
	extent_info.is_new_extent = true;
	extent_info.qgroup_reserved = ret;
	...

Note how the variable @ret is abused here, and if anyone is adding code
just after btrfs_qgroup_release_data() call, it's super easy to
overwrite the @ret and cause tons of qgroup related bugs.

Fix such abuse by introducing new variable @qgroup_released, so that we
won't reuse the existing variable @ret.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/inode.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10467,6 +10467,7 @@ static int insert_prealloc_file_extent(s
 	struct btrfs_file_extent_item stack_fi;
 	u64 start = ins->objectid;
 	u64 len = ins->offset;
+	int qgroup_released;
 	int ret;
 
 	memset(&stack_fi, 0, sizeof(stack_fi));
@@ -10479,11 +10480,11 @@ static int insert_prealloc_file_extent(s
 	btrfs_set_stack_file_extent_compression(&stack_fi, BTRFS_COMPRESS_NONE);
 	/* Encryption and other encoding is reserved and all 0 */
 
-	ret = btrfs_qgroup_release_data(inode, file_offset, len);
-	if (ret < 0)
-		return ret;
+	qgroup_released = btrfs_qgroup_release_data(inode, file_offset, len);
+	if (qgroup_released < 0)
+		return qgroup_released;
 	return insert_reserved_file_extent(trans, inode, file_offset,
-					   &stack_fi, ret);
+					   &stack_fi, qgroup_released);
 }
 static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
 				       u64 start, u64 num_bytes, u64 min_size,