Commit 566d774a authored by John Hubbard's avatar John Hubbard Committed by Linus Torvalds

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.
Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
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/20200211001536.1027652-4-jhubbard@nvidia.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 86dfbed4
......@@ -102,6 +102,15 @@ static inline void page_ref_sub(struct page *page, int nr)
__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);
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment