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Date:   Wed, 20 Jul 2022 04:18:51 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Jeremy Bongio <bongiojp@gmail.com>
Cc:     Ted Tso <tytso@mit.edu>, linux-ext4@vger.kernel.org,
        linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v4] Add ioctls to get/set the ext4 superblock uuid.
Message-ID: <Ytd0G0glVWdv+iaD@casper.infradead.org>
References: <20220719234131.235187-1-bongiojp@gmail.com>
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On Tue, Jul 19, 2022 at 04:41:31PM -0700, Jeremy Bongio wrote:
> +/*
> + * Structure for EXT4_IOC_GETFSUUID/EXT4_IOC_SETFSUUID
> + */
> +struct fsuuid {
> +	__u32       fsu_len;
> +	__u32       fsu_flags;
> +	__u8        fsu_uuid[];
> +};

A UUID has a defined size (128 bits):
https://en.wikipedia.org/wiki/Universally_unique_identifier

Why are we defining flags and len?