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Date: Fri, 31 Jan 2020 19:40:26 -0800 From: John Hubbard <jhubbard@...dia.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Al Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@...radead.org>, Dan Williams <dan.j.williams@...el.com>, Dave Chinner <david@...morbit.com>, Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>, Jason Gunthorpe <jgg@...pe.ca>, Jonathan Corbet <corbet@....net>, Jérôme Glisse <jglisse@...hat.com>, "Kirill A . Shutemov" <kirill@...temov.name>, Michal Hocko <mhocko@...e.com>, Mike Kravetz <mike.kravetz@...cle.com>, Shuah Khan <shuah@...nel.org>, Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>, <linux-doc@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>, <linux-rdma@...r.kernel.org>, <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, John Hubbard <jhubbard@...dia.com> Subject: [PATCH v3 09/12] mm: dump_page(): better 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. Signed-off-by: John Hubbard <jhubbard@...dia.com> --- Documentation/core-api/pin_user_pages.rst | 7 +++++ mm/debug.c | 34 +++++++++++++++++------ 2 files changed, 33 insertions(+), 8 deletions(-) diff --git a/Documentation/core-api/pin_user_pages.rst b/Documentation/core-api/pin_user_pages.rst index 3f72b1ea1104..dd21ea140ef4 100644 --- a/Documentation/core-api/pin_user_pages.rst +++ b/Documentation/core-api/pin_user_pages.rst @@ -215,6 +215,13 @@ Those are both going to show zero, unless CONFIG_DEBUG_VM is set. This is because there is a noticeable performance drop in unpin_user_page(), when they are activated. +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 beb1c59d784b..db81b11345be 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -57,10 +57,20 @@ static void __dump_tail_page(struct page *page, int mapcount) page, page_ref_count(page), mapcount, page->mapping, page_to_pgoff(page)); } else { - pr_warn("page:%px compound refcount:%d mapcount:%d mapping:%px " - "index:%#lx compound_mapcount:%d\n", - page, page_ref_count(head), mapcount, head->mapping, - page_to_pgoff(head), compound_mapcount(page)); + if (hpage_pincount_available(page)) + pr_warn("page:%px compound refcount:%d mapcount:%d " + "mapping:%px index:%#lx compound_mapcount:%d " + "compound_pincount:%d\n", + page, page_ref_count(head), mapcount, + head->mapping, page_to_pgoff(head), + compound_mapcount(page), + compound_pincount(page)); + else + pr_warn("page:%px compound refcount:%d mapcount:%d " + "mapping:%px index:%#lx compound_mapcount:%d\n", + page, page_ref_count(head), mapcount, + head->mapping, page_to_pgoff(head), + compound_mapcount(page)); } if (page_ref_count(page) != 0) @@ -103,10 +113,18 @@ void __dump_page(struct page *page, const char *reason) if (PageTail(page)) __dump_tail_page(page, mapcount); - else - pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n", - page, page_ref_count(page), mapcount, - page->mapping, page_to_pgoff(page)); + else { + if (hpage_pincount_available(page)) + pr_warn("page:%px refcount:%d mapcount:%d mapping:%px " + "index:%#lx compound pincount: %d\n", + page, page_ref_count(page), mapcount, + page->mapping, page_to_pgoff(page), + compound_pincount(page)); + else + pr_warn("page:%px refcount:%d mapcount:%d mapping:%px " + "index:%#lx\n", page, page_ref_count(page), + mapcount, page->mapping, page_to_pgoff(page)); + } if (PageKsm(page)) type = "ksm "; else if (PageAnon(page)) -- 2.25.0
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