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SubjectRe: [RFC] weird semantics of SG_DXFER_TO_FROM_DEV in BLK_DEV_SKD (drivers/block/skd*)
On Mon, Apr 04, 2016 at 06:16:12PM +0100, Al Viro wrote:

> will see NULL map_data; the ->from_user case is sg_start_req() stuff. IOW,
> SG_IO behaviour for /dev/sg* is different from the generic one...

While we are at it: in bio_map_user_iov() we have
iov_for_each(iov, i, *iter) {
unsigned long uaddr = (unsigned long) iov.iov_base;
unsigned long len = iov.iov_len;
unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;

/*
* Overflow, abort
*/
if (end < start)
return ERR_PTR(-EINVAL);

nr_pages += end - start;
/*
* buffer must be aligned to at least hardsector size for now
*/
if (uaddr & queue_dma_alignment(q))
return ERR_PTR(-EINVAL);
}

Do we only care about the iov_base alignment? IOW, shouldn't we check for
iov_len being a multiple of queue_dma_alignment(q) as well?

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