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Date:   Fri, 19 Jul 2019 14:13:37 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-kernel@vger.kernel.org,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Jani Nikula <jani.nikula@intel.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Hannes Reinecke <hare@suse.com>,
        Omar Sandoval <osandov@fb.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH] [v2] blkdev: always export SECTOR_SHIFT
Message-ID: <20190719121336.GB28960@lst.de>
References: <20190719113139.4005262-1-arnd@arndb.de>
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> +/*
> + * The basic unit of block I/O is a sector. It is used in a number of contexts
> + * in Linux (blk, bio, genhd). The size of one sector is 512 = 2**9
> + * bytes. Variables of type sector_t represent an offset or size that is a
> + * multiple of 512 bytes. Hence these two constants.
> + */
> +#ifndef SECTOR_SHIFT
> +#define SECTOR_SHIFT 9
> +#endif
> +#ifndef SECTOR_SIZE
> +#define SECTOR_SIZE (1 << SECTOR_SHIFT)
> +#endif

While we're at it we really should drop the ifndefs.

Otherwise looks good.

In fact given that sector_t is in linux/types.h I wonder if these
should just move there.