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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.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200211001536.1027652-13-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
John Hubbard 2020-04-01 21:05:52 -07:00 committed by Linus Torvalds
parent 6197ab984b
commit dc8fb2f282
2 changed files with 23 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/core-api/pin_user_pages.rst
View File

@ -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
==========

21
mm/debug.c
View File

@ -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));
}
else
pr_warn("page:%px refcount:%d mapcount:%d mapping:%p index:%#lx\n",
page, page_ref_count(page), mapcount,