linux-kernel - Re: [RFC PATCH v2 1/7] statx: add I/O alignment information

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Message-ID: <87r14ffivd.fsf@oldenburg.str.redhat.com>
Date:   Fri, 27 May 2022 11:02:46 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-xfs@...r.kernel.org,
        linux-api@...r.kernel.org, linux-fscrypt@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Keith Busch <kbusch@...nel.org>
Subject: Re: [RFC PATCH v2 1/7] statx: add I/O alignment information

* Eric Biggers:

> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index 1500a0f58041a..f822b23e81091 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -124,9 +124,13 @@ struct statx {
>  	__u32	stx_dev_minor;
>  	/* 0x90 */
>  	__u64	stx_mnt_id;
> -	__u64	__spare2;
> +	__u32	stx_mem_align_dio;	/* Memory buffer alignment for direct I/O */
> +	__u32	stx_offset_align_dio;	/* File offset alignment for direct I/O */
>  	/* 0xa0 */
> -	__u64	__spare3[12];	/* Spare space for future expansion */
> +	__u32	stx_offset_align_optimal; /* Optimal file offset alignment for I/O */
> +	__u32	__spare2;
> +	/* 0xa8 */
> +	__u64	__spare3[11];	/* Spare space for future expansion */
>  	/* 0x100 */
>  };

Are 32 bits enough?  Would it make sense to store the base-2 logarithm
instead?

Thanks,
Florian