On Mon, Feb 10, 2020 at 04:15:36PM -0800, John Hubbard wrote:
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.
Cc: Jan Kara jack@suse.cz Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Matthew Wilcox willy@infradead.org Signed-off-by: John Hubbard jhubbard@nvidia.com
Documentation/core-api/pin_user_pages.rst | 7 +++++++ mm/debug.c | 21 ++++++++++++++++----- 2 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core-api/pin_user_pages.rst index 5c8a5f89756b..2e939ff10b86 100644 --- a/Documentation/core-api/pin_user_pages.rst +++ b/Documentation/core-api/pin_user_pages.rst @@ -238,6 +238,13 @@ long-term [R]DMA pins in place, or during pin/unpin transitions. (...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
diff --git a/mm/debug.c b/mm/debug.c index f5ffb0784559..2189357f0987 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -85,11 +85,22 @@ void __dump_page(struct page *page, const char *reason) 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));}
Have you considered using pr_cont() here. I guess it would be easier to read.
You can use my Ack anyway.
else pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n", page, page_ref_count(page), mapcount, -- 2.25.0