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Date:   Fri, 21 Apr 2023 23:49:43 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     hughd@google.com, akpm@linux-foundation.org, brauner@kernel.org,
        djwong@kernel.org, p.raghav@samsung.com, da.gomez@samsung.com,
        a.manzanares@samsung.com, dave@stgolabs.net, yosryahmed@google.com,
        keescook@chromium.org, hare@suse.de, kbusch@kernel.org,
        patches@lists.linux.dev, linux-block@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC 4/8] shmem: add helpers to get block size
Message-ID: <ZEMTB4uKgKJKQRHo@casper.infradead.org>
References: <20230421214400.2836131-1-mcgrof@kernel.org>
 <20230421214400.2836131-5-mcgrof@kernel.org>
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On Fri, Apr 21, 2023 at 02:43:56PM -0700, Luis Chamberlain wrote:
>  struct shmem_sb_info {
> +#ifdef CONFIG_TMPFS
> +	u64 blocksize;
> +#endif

u64?  You're planning on supporting a blocksize larger than 2GB?

I would store block_order (in an unsigned char) and then you can avoid
the call to ffs(), at the expense of doing 1UL << sbi->block_order;