linux-kernel - Re: [PATCH v6 md-6.18 11/11] md/md-llbitmap: introduce new lockless bitmap

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Message-ID: <65a2856a-7e2f-111a-c92e-7941206ad006@huaweicloud.com>
Date: Wed, 27 Aug 2025 11:44:57 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>, Yu Kuai <yukuai1@...weicloud.com>
Cc: hch@...radead.org, corbet@....net, agk@...hat.com, snitzer@...nel.org,
 mpatocka@...hat.com, song@...nel.org, xni@...hat.com, hare@...e.de,
 linan122@...wei.com, colyli@...nel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, dm-devel@...ts.linux.dev,
 linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 johnny.chenyi@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v6 md-6.18 11/11] md/md-llbitmap: introduce new lockless
 bitmap

Hi,

在 2025/08/26 17:52, Paul Menzel 写道:
> It’d be great if you could motivate, why a lockless bitmap is needed  > compared to the current implemention.

Se the performance test, old bitmap have global spinlock and is bad with
fast disk.

[snip the typo part]

> How can/should this patch be tested/benchmarked?

There is pending mdadm patch, rfc verion can be used. Will work on
formal version after this set is applied.

> --- a/drivers/md/md-bitmap.h
> +++ b/drivers/md/md-bitmap.h
> @@ -9,10 +9,26 @@
>    #define BITMAP_MAGIC 0x6d746962
> +/*
> + * version 3 is host-endian order, this is deprecated and not used for new
> + * array
> + */
> +#define BITMAP_MAJOR_LO        3
> +#define BITMAP_MAJOR_HOSTENDIAN    3
> +/* version 4 is little-endian order, the default value */
> +#define BITMAP_MAJOR_HI        4
> +/* version 5 is only used for cluster */
> +#define BITMAP_MAJOR_CLUSTERED    5  > Move this to the header in a separate patch?

I prefer not, old bitmap use this as well.

Thanks,
Kuai