Re: [PATCH v11 01/25] mm/gup: factor out duplicate code from four routines
From: Kirill A. Shutemov <hidden>
Date: 2019-12-18 15:52:22
Also in:
bpf, dri-devel, kvm, linux-doc, linux-fsdevel, linux-kselftest, linux-media, linux-mm, linux-rdma, linuxppc-dev, lkml, netdev
On Mon, Dec 16, 2019 at 02:25:13PM -0800, John Hubbard wrote:
+static void put_compound_head(struct page *page, int refs)
+{
+ /* Do a get_page() first, in case refs == page->_refcount */
+ get_page(page);
+ page_ref_sub(page, refs);
+ put_page(page);
+}It's not terribly efficient. Maybe something like: VM_BUG_ON_PAGE(page_ref_count(page) < ref, page); if (refs > 2) page_ref_sub(page, refs - 1); put_page(page); ? -- Kirill A. Shutemov