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Date: Mon, 9 Nov 2009 22:33:38 +0100 From: Karel Zak <kzak@...hat.com> To: "Andries E. Brouwer" <Andries.Brouwer@....nl> Cc: Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: [PATCH 1/2] partitions: use sector size for EFI GPT On Mon, Nov 09, 2009 at 08:58:32PM +0100, Andries E. Brouwer wrote: > static size_t > read_lba(struct block_device *bdev, u64 lba, u8 * buffer, size_t count) > { > size_t totalreadcount = 0; > sector_t n = lba * (bdev_logical_block_size(bdev) / 512); > > if (!bdev || !buffer || lba > last_lba(bdev)) > return 0; > > while (count) { > int copied = 512; > Sector sect; > unsigned char *data = read_dev_sector(bdev, n++, §); > if (!data) > break; > if (copied > count) > copied = count; > memcpy(buffer, data, copied); > put_dev_sector(sect); > buffer += copied; > totalreadcount +=copied; > count -= copied; > } > return totalreadcount; > } > > Ugly - it looks as if you call read_dev_sector 8 times and each time Yes, the function is really not elegant, but it follows the way how all fs/partitions code reads sectors from disks. > do a put_dev_sector afterwards to forget it again. Doesnt that mean > that in order to read a 4096-byte sector the kernel goes to the hardware > 8 times? read_dev_sector() works with 512-byte sectors and it's interface to read_mapping_page() which works with pages from cache. Karel -- Karel Zak <kzak@...hat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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