From: John Hubbard <jhubbard@xxxxxxxxxx> Subject: mm: dump_page(): additional diagnostics for huge pinned pages As part of pin_user_pages() and related API calls, pages are "dma-pinned". For the case of compound pages of order > 1, the per-page accounting of dma pins is accomplished via the 3rd struct page in the compound page. In order to support debugging of any pin_user_pages()- related problems, enhance dump_page() so as to report the pin count in that case. Documentation/core-api/pin_user_pages.rst is also updated accordingly. Link: http://lkml.kernel.org/r/20200211001536.1027652-13-jhubbard@xxxxxxxxxx Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Ira Weiny <ira.weiny@xxxxxxxxx> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/core-api/pin_user_pages.rst | 7 ++++++ mm/debug.c | 21 +++++++++++++++----- 2 files changed, 23 insertions(+), 5 deletions(-) --- a/Documentation/core-api/pin_user_pages.rst~mm-dump_page-additional-diagnostics-for-huge-pinned-pages +++ a/Documentation/core-api/pin_user_pages.rst @@ -238,6 +238,13 @@ long-term [R]DMA pins in place, or durin (...unless it was already out of balance due to a long-term RDMA pin being in place.) +Other diagnostics +================= + +dump_page() has been enhanced slightly, to handle these new counting fields, and +to better report on compound pages in general. Specifically, for compound pages +with order > 1, the exact (hpage_pinned_refcount) pincount is reported. + References ========== --- a/mm/debug.c~mm-dump_page-additional-diagnostics-for-huge-pinned-pages +++ a/mm/debug.c @@ -85,11 +85,22 @@ void __dump_page(struct page *page, cons mapcount = PageSlab(head) ? 0 : page_mapcount(page); if (compound) - pr_warn("page:%px refcount:%d mapcount:%d mapping:%p " - "index:%#lx head:%px order:%u compound_mapcount:%d\n", - page, page_ref_count(head), mapcount, - mapping, page_to_pgoff(page), head, - compound_order(head), compound_mapcount(page)); + if (hpage_pincount_available(page)) { + pr_warn("page:%px refcount:%d mapcount:%d mapping:%p " + "index:%#lx head:%px order:%u " + "compound_mapcount:%d compound_pincount:%d\n", + page, page_ref_count(head), mapcount, + mapping, page_to_pgoff(page), head, + compound_order(head), compound_mapcount(page), + compound_pincount(page)); + } else { + pr_warn("page:%px refcount:%d mapcount:%d mapping:%p " + "index:%#lx head:%px order:%u " + "compound_mapcount:%d\n", + page, page_ref_count(head), mapcount, + mapping, page_to_pgoff(page), head, + compound_order(head), compound_mapcount(page)); + } else pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n", page, page_ref_count(page), mapcount, _
