Re: [PATCH v4 04/12] mm: introduce page_ref_sub_return()
From: Jan Kara <jack@suse.cz>
Date: 2020-02-05 09:23:27
Also in:
linux-fsdevel, linux-kselftest, linux-mm, linux-rdma, lkml
On Tue 04-02-20 15:41:09, John Hubbard wrote:
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: John Hubbard <jhubbard@nvidia.com>
Looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza
quoted hunk ↗ jump to hunk
--- include/linux/page_ref.h | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 14d14beb1f7f..a0e171265b79 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h@@ -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)) + __page_ref_mod_and_return(page, -nr, ret); + return ret; +} + static inline void page_ref_inc(struct page *page) { atomic_inc(&page->_refcount);-- 2.25.0
-- Jan Kara [off-list ref] SUSE Labs, CR