The patch titled
Subject: mm: introduce page_ref_sub_return()
has been added to the -mm tree. Its filename is
mm-introduce-page_ref_sub_return.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-introduce-page_ref_sub_return.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-introduce-page_ref_sub_return.patch
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------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: mm: introduce page_ref_sub_return()
An upcoming patch requires subtracting a large chunk of refcounts from a
page, and checking what the resulting refcount is. This is a little
different than the usual "check for zero refcount" that many of the page
ref functions already do. However, it is similar to a few other routines
that (like this one) are generally useful for things such as 1-based
refcounting.
Add page_ref_sub_return(), that subtracts a chunk of refcounts atomically,
and returns an atomic snapshot of the result.
Link: http://lkml.kernel.org/r/20200211001536.1027652-4-jhubbard@xxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
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>
---
include/linux/page_ref.h | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/include/linux/page_ref.h~mm-introduce-page_ref_sub_return
+++ a/include/linux/page_ref.h
@@ -102,6 +102,15 @@ static inline void page_ref_sub(struct p
__page_ref_mod(page, -nr);
}
+static inline int page_ref_sub_return(struct page *page, int nr)
+{
+ int ret = atomic_sub_return(nr, &page->_refcount);
+
+ if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return))
+ __page_ref_mod_and_return(page, -nr, ret);
+ return ret;
+}
+
static inline void page_ref_inc(struct page *page)
{
atomic_inc(&page->_refcount);
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
mm-gup-split-get_user_pages_remote-into-two-routines.patch
mm-gup-pass-a-flags-arg-to-__gup_device_-functions.patch
mm-introduce-page_ref_sub_return.patch
mm-gup-pass-gup-flags-to-two-more-routines.patch
mm-gup-require-foll_get-for-get_user_pages_fast.patch
mm-gup-track-foll_pin-pages.patch
mm-gup-page-hpage_pinned_refcount-exact-pin-counts-for-huge-pages.patch
mm-gup-proc-vmstat-pin_user_pages-foll_pin-reporting.patch
mm-gup_benchmark-support-pin_user_pages-and-related-calls.patch
selftests-vm-run_vmtests-invoke-gup_benchmark-with-basic-foll_pin-coverage.patch
mm-dump_page-additional-diagnostics-for-huge-pinned-pages.patch
