On 31 Mar 2021, at 12:44, Matthew Wilcox wrote:
On Mon, Mar 29, 2021 at 11:39:32AM -0400, Zi Yan wrote:
- for (off_cur = off_start; off_cur < off_end;) {
struct page *fpage = pagecache_get_page(mapping, off_cur,FGP_ENTRY | FGP_HEAD, 0);if (xa_is_value(fpage) || !fpage) {off_cur += PAGE_SIZE;continue;}if (!is_transparent_hugepage(fpage)) {off_cur += PAGE_SIZE;goto next;}total++;off_cur = fpage->index + thp_size(fpage);That can't be right. fpage->index is in units of pages and thp_size is in units of bytes. I wish C had a better type system. I think you meant:
off_cur = fpage->index + thp_nr_pages(fpage);Also, I think this loop would read better as ...
for (index = off_start; index < off_end; index += nr_pages) { struct page *fpage = pagecache_get_page(mapping, index, FGP_ENTRY | FGP_HEAD, 0); nr_pages = 1; if (xa_is_value(fpage) || !fpage) continue; if (!is_transparent_hugepage(fpage)) goto next; total++; nr_pages = thp_nr_pages(fpage); ...
Thanks for catching this! I mixed this with looping through VMA, which is in units of bytes. I will fix this and use your suggested loop code.
— Best Regards, Yan Zi