btrfs: qgroup: delete unnecessary check in btrfs_qgroup_check_inherit()

This check "if (inherit->num_qgroups > PAGE_SIZE)" is confusing and
unnecessary.

The problem with the check is that static checkers flag it as a
potential mixup of between units of bytes vs number of elements.
Fortunately, the check can safely be deleted because the next check is
correct and applies an even stricter limit:

	if (size != struct_size(inherit, qgroups, inherit->num_qgroups))
		return -EINVAL;

The "inherit" struct ends in a variable array of __u64 and
"inherit->num_qgroups" is the number of elements in the array.  At the
start of the function we check that:

	if (size < sizeof(*inherit) || size > PAGE_SIZE)
		return -EINVAL;

Thus, since we verify that the whole struct fits within one page, that
means that the number of elements in the inherit->qgroups[] array must
be less than PAGE_SIZE.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 40e5f7f2fcb7f852f22729fefa640895f57d9933..dbb114be8e79f082a20954b120cff885b978dbdb 100644 (file)
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3064,9 +3064,6 @@ int btrfs_qgroup_check_inherit(struct btrfs_fs_info *fs_info,
        if (inherit->num_ref_copies > 0 || inherit->num_excl_copies > 0)
                return -EINVAL;
 
-       if (inherit->num_qgroups > PAGE_SIZE)
-               return -EINVAL;
-
        if (size != struct_size(inherit, qgroups, inherit->num_qgroups))
                return -EINVAL;