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SubjectRe: [PATCH] bio: fix argument of __bio_add_page() for max_sectors > 0xffff
2013/11/19 Jens Axboe <>:
> On 11/18/2013 06:11 AM, Akinobu Mita wrote:
>> The data type of max_sectors and max_hw_sectors in queue settings are
>> unsigned int. But these values are passed to __bio_add_page() as an
>> argument whose data type is unsigned short. In the worst case such as
>> max_sectors is 0x10000, bio_add_page() can't add a page and IOs can't
>> proceed.
> Thanks, added. Even at 512b sectors, 0xffff sectors would be a huuuuge
> page. So I don't think we'd ever see this bug hit, iirc huge pages are
> still broken down for IO. But it's better to be safe...

I hit this when I was trying to change the data type of max_sectors in
scsi host settings from 16-bit to 32-bit.

BTW, I found that BLKSECTGET only returns 16-bit of max_sectors. Should
we need the change like below?

- return put_ushort(arg, queue_max_sectors(bdev_get_queue(bdev)));
+ max_sectors = min(0xffff,
+ queue_max_sectors(bdev_get_queue(bdev)));
+ return put_ushort(arg, max_sectors);

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