[PATCH 1/2] btrfs: use a dedicated variable for qgroup released data rsv for insert_prealloc_file_extent()

[Qu Wenruo]

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 <w...@suse.com>
---
I really want to go back time and slap my face. That damn naming,
especially that "extent_info.qgroup_reserved = ret", wasted too long
time.

What the heck I was doing in the past??
---
 fs/btrfs/inode.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4f2f1e932751..4e9717c29451 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9873,6 +9873,7 @@ static struct btrfs_trans_handle 
*insert_prealloc_file_extent(
        struct btrfs_path *path;
        u64 start = ins->objectid;
        u64 len = ins->offset;
+       int qgroup_released;
        int ret;
 
        memset(&stack_fi, 0, sizeof(stack_fi));
@@ -9885,14 +9886,14 @@ static struct btrfs_trans_handle 
*insert_prealloc_file_extent(
        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 ERR_PTR(ret);
+       qgroup_released = btrfs_qgroup_release_data(inode, file_offset, len);
+       if (qgroup_released < 0)
+               return ERR_PTR(qgroup_released);
 
        if (trans) {
                ret = insert_reserved_file_extent(trans, inode,
                                                  file_offset, &stack_fi,
-                                                 true, ret);
+                                                 true, qgroup_released);
                if (ret)
                        return ERR_PTR(ret);
                return trans;
@@ -9905,7 +9906,7 @@ static struct btrfs_trans_handle 
*insert_prealloc_file_extent(
        extent_info.file_offset = file_offset;
        extent_info.extent_buf = (char *)&stack_fi;
        extent_info.is_new_extent = true;
-       extent_info.qgroup_reserved = ret;
+       extent_info.qgroup_reserved = qgroup_released;
        extent_info.insertions = 0;
 
        path = btrfs_alloc_path();
-- 
2.30.1