linux-kernel - Re: [RFC 8/8] shmem: add support to customize block size on multiple PAGE

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Date:   Fri, 21 Apr 2023 22:10:39 -0700
From:   Jane Chu <jane.chu@...cle.com>
To:     Luis Chamberlain <mcgrof@...nel.org>, hughd@...gle.com,
        akpm@...ux-foundation.org, willy@...radead.org, brauner@...nel.org,
        djwong@...nel.org
Cc:     p.raghav@...sung.com, da.gomez@...sung.com,
        a.manzanares@...sung.com, dave@...olabs.net, yosryahmed@...gle.com,
        keescook@...omium.org, hare@...e.de, kbusch@...nel.org,
        patches@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 8/8] shmem: add support to customize block size on multiple
 PAGE_SIZE


On 4/21/2023 2:44 PM, Luis Chamberlain wrote:
[..]
> +		/*
> +		 * We cap this to allow a block to be at least allowed to
> +		 * be allocated using the buddy allocator. That's MAX_ORDER
> +		 * pages. So 4 MiB on x86_64.

8 MiB? since MAX_ORDER is 11.

> +		 */
> +		if (ctx->blocksize > (1 << (MAX_ORDER + PAGE_SHIFT)))
> +			goto bad_value; > +
> +		/* The blocksize must be a multiple of the page size so must be aligned */
> +		if (!PAGE_ALIGNED(ctx->blocksize))
> +			goto bad_value;
> +		break;
>   	}
>   	return 0;

-jane