linux-kernel - Re: [PATCH 1/3] btrfs: rst: remove encoding field from stripe

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Message-ID: <c7246728-aadb-4699-8fdf-060502c1092a@wdc.com>
Date: Tue, 11 Jun 2024 16:33:19 +0000
From: Johannes Thumshirn <Johannes.Thumshirn@....com>
To: "dsterba@...e.cz" <dsterba@...e.cz>, Johannes Thumshirn <jth@...nel.org>
CC: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba
	<dsterba@...e.com>, "linux-btrfs@...r.kernel.org"
	<linux-btrfs@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] btrfs: rst: remove encoding field from stripe_extent

On 11.06.24 16:37, David Sterba wrote:
> On Mon, Jun 10, 2024 at 10:40:25AM +0200, Johannes Thumshirn wrote:
>> -#define BTRFS_STRIPE_RAID5	5
>> -#define BTRFS_STRIPE_RAID6	6
>> -#define BTRFS_STRIPE_RAID1C3	7
>> -#define BTRFS_STRIPE_RAID1C4	8
>> -
>>   struct btrfs_stripe_extent {
>> -	__u8 encoding;
>> -	__u8 reserved[7];
>>   	/* An array of raid strides this stripe is composed of. */
>> -	struct btrfs_raid_stride strides[];
>> +	__DECLARE_FLEX_ARRAY(struct btrfs_raid_stride, strides);
> 
> Is there a reason to use the __ underscore macro? I see no difference
> between that and DECLARE_FLEX_ARRAY and underscore usually means that
> it's special in some way.
> 

Yes, the __ version is for UAPI, like __u8 or __le32 and so on.