Messages in this thread | | | From | David Howells <> | Subject | Re: [RFC][PATCH] iov_iter: Add ITER_MAPPING | Date | Fri, 24 Jan 2020 14:58:37 +0000 |
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Okay, so this then?
#define iterate_mapping(i, n, __v, skip, STEP) { \ struct page *page; \ size_t wanted = n, seg, offset; \ loff_t start = i->mapping_start + skip; \ pgoff_t index = start >> PAGE_SHIFT; \ \ XA_STATE(xas, &i->mapping->i_pages, index); \ \ rcu_read_lock(); \ for (page = xas_load(&xas); page; page = xas_next(&xas)) { \ if (xas_retry(&xas, page)) \ continue; \ if (WARN_ON(xa_is_value(page))) \ break; \ if (WARN_ON(PageHuge(page))) \ break; \ __v.bv_page = find_subpage(page, xas.xa_index); \ offset = (i->mapping_start + skip) & ~PAGE_MASK; \ seg = PAGE_SIZE - offset; \ __v.bv_offset = offset; \ __v.bv_len = min(n, seg); \ (void)(STEP); \ n -= __v.bv_len; \ skip += __v.bv_len; \ if (n == 0) \ break; \ } \ rcu_read_unlock(); \ n = wanted - n; \ }
> We could also have an ITER_XARRAY which you just pass &mapping->i_pages > to. I don't think you use any other part of the mapping, so that would > be a more generic version that is equally efficient.
I could give that a go. Out of interest, are there any other users of xarray that might use it that don't have a mapping handy?
David
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