linux-kernel - Re: [PATCH v6 05/10] block: Add core atomic write support

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Date: Tue, 26 Mar 2024 10:11:50 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: John Garry <john.g.garry@...cle.com>, axboe@...nel.dk, kbusch@...nel.org,
 hch@....de, sagi@...mberg.me, jejb@...ux.ibm.com,
 martin.petersen@...cle.com, djwong@...nel.org, viro@...iv.linux.org.uk,
 brauner@...nel.org, dchinner@...hat.com, jack@...e.cz
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-nvme@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
 tytso@....edu, jbongio@...gle.com, linux-scsi@...r.kernel.org,
 ojaswin@...ux.ibm.com, linux-aio@...ck.org, linux-btrfs@...r.kernel.org,
 io-uring@...r.kernel.org, nilay@...ux.ibm.com, ritesh.list@...il.com,
 willy@...radead.org, Himanshu Madhani <himanshu.madhani@...cle.com>
Subject: Re: [PATCH v6 05/10] block: Add core atomic write support

Hi,

On 3/26/24 06:38, John Garry wrote:
> diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
> index 1fe9a553c37b..4c775f4bdefe 100644
> --- a/Documentation/ABI/stable/sysfs-block
> +++ b/Documentation/ABI/stable/sysfs-block
> @@ -21,6 +21,58 @@ Description:
>  		device is offset from the internal allocation unit's
>  		natural alignment.
>  
> +What:		/sys/block/<disk>/atomic_write_max_bytes
> +Date:		February 2024
> +Contact:	Himanshu Madhani <himanshu.madhani@...cle.com>
> +Description:
> +		[RO] This parameter specifies the maximum atomic write
> +		size reported by the device. This parameter is relevant
> +		for merging of writes, where a merged atomic write
> +		operation must not exceed this number of bytes.
> +		This parameter may be greater to the value in

		                              than

> +		atomic_write_unit_max_bytes as
> +		atomic_write_unit_max_bytes will be rounded down to a
> +		power-of-two and atomic_write_unit_max_bytes may also be
> +		limited by some other queue limits, such as max_segments.
> +		This parameter - along with atomic_write_unit_min_bytes
> +		and atomic_write_unit_max_bytes - will not be larger than
> +		max_hw_sectors_kb, but may be larger than max_sectors_kb.
> +
> +
> +What:		/sys/block/<disk>/atomic_write_unit_min_bytes
> +Date:		February 2024
> +Contact:	Himanshu Madhani <himanshu.madhani@...cle.com>
> +Description:
> +		[RO] This parameter specifies the smallest block which can
> +		be written atomically with an atomic write operation. All
> +		atomic write operations must begin at a
> +		atomic_write_unit_min boundary and must be multiples of
> +		atomic_write_unit_min. This value must be a power-of-two.
> +
> +
> +What:		/sys/block/<disk>/atomic_write_unit_max_bytes
> +Date:		February 2024
> +Contact:	Himanshu Madhani <himanshu.madhani@...cle.com>
> +Description:
> +		[RO] This parameter defines the largest block which can be
> +		written atomically with an atomic write operation. This
> +		value must be a multiple of atomic_write_unit_min and must
> +		be a power-of-two. This value will not be larger than
> +		atomic_write_max_bytes.
> +
> +
> +What:		/sys/block/<disk>/atomic_write_boundary_bytes
> +Date:		February 2024
> +Contact:	Himanshu Madhani <himanshu.madhani@...cle.com>
> +Description:
> +		[RO] A device may need to internally split I/Os which
> +		straddle a given logical block address boundary. In that
> +		case a single atomic write operation will be processed as
> +		one of more sub-operations which each complete atomically.

		    or

> +		This parameter specifies the size in bytes of the atomic
> +		boundary if one is reported by the device. This value must
> +		be a power-of-two.

-- 
#Randy