linux-kernel - RE: [PATCH v4 3/5] block: add ioctl to read the disk sequence number

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Date:   Mon, 12 Jul 2021 19:22:43 +0000
From:   "Elliott, Robert (Servers)" <elliott@....com>
To:     'Matteo Croce' <mcroce@...ux.microsoft.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Lennart Poettering" <lennart@...ttering.net>,
        Luca Boccassi <bluca@...ian.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Damien Le Moal <damien.lemoal@....com>,
        Tejun Heo <tj@...nel.org>,
        Javier González <javier@...igon.com>,
        Niklas Cassel <niklas.cassel@....com>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Hannes Reinecke <hare@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Hellwig <hch@...radead.org>,
        JeffleXu <jefflexu@...ux.alibaba.com>
Subject: RE: [PATCH v4 3/5] block: add ioctl to read the disk sequence number



> -----Original Message-----
> From: Matteo Croce <mcroce@...ux.microsoft.com>
> Sent: Sunday, July 11, 2021 12:54 PM
...
> Subject: [PATCH v4 3/5] block: add ioctl to read the disk sequence number
> 
> From: Matteo Croce <mcroce@...rosoft.com>
> 
> Add a new BLKGETDISKSEQ ioctl which retrieves the disk sequence number
> from the genhd structure.
...


Given:
    static int put_u64(u64 __user *argp, u64 val)
    {
        return put_user(val, argp);
    }

> diff --git a/block/ioctl.c b/block/ioctl.c
> index 24beec9ca9c9..0c3a4a53fa11 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -469,6 +469,8 @@ static int blkdev_common_ioctl(struct block_device
> *bdev, fmode_t mode,
>  				BLKDEV_DISCARD_SECURE);
...

> +	case BLKGETDISKSEQ:
> +		return put_u64(argp, bdev->bd_disk->diskseq);

How does that work on a system in which int is 32 bits?