Re: [PATCH v4 3/5] block: add ioctl to read the disk sequence number

[Matteo Croce <mcroce@linux.microsoft.com>]

On Mon, 12 Jul 2021 19:22:43 +0000
"Elliott, Robert (Servers)" <elliott@hpe.com> wrote:

> 
> 
> > -----Original Message-----
> > From: Matteo Croce <mcroce@linux.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@microsoft.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?
> 
> 

Hi,

what's the difference with this?

	case BLKGETSIZE64:
		return put_u64(argp, i_size_read(bdev->bd_inode));

The returned int is an error code, not the diskseq value itself, e.g.

	case BLKFRAGET:
		if (!argp)
			return -EINVAL;

Regards,
-- 
per aspera ad upstream