From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932233AbdLOOK7 (ORCPT ); Fri, 15 Dec 2017 09:10:59 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:54756 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932175AbdLOOKx (ORCPT ); Fri, 15 Dec 2017 09:10:53 -0500 From: Christoph Hellwig To: Dan Williams Cc: =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Logan Gunthorpe , linux-nvdimm@lists.01.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 12/17] mm: optimize dev_pagemap reference counting around get_dev_pagemap Date: Fri, 15 Dec 2017 15:09:42 +0100 Message-Id: <20171215140947.26075-13-hch@lst.de> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20171215140947.26075-1-hch@lst.de> References: <20171215140947.26075-1-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Change the calling convention so that get_dev_pagemap always consumes the previous reference instead of doing this using an explicit earlier call to put_dev_pagemap in the callers. The callers will still need to put the final reference after finishing the loop over the pages. Signed-off-by: Christoph Hellwig Reviewed-by: Logan Gunthorpe --- kernel/memremap.c | 17 +++++++++-------- mm/gup.c | 7 +++++-- 2 files changed, 14 insertions(+), 10 deletions(-) diff --git a/kernel/memremap.c b/kernel/memremap.c index 43d94db97ff4..26764085785d 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -506,22 +506,23 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) * @pfn: page frame number to lookup page_map * @pgmap: optional known pgmap that already has a reference * - * @pgmap allows the overhead of a lookup to be bypassed when @pfn lands in the - * same mapping. + * If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap + * is non-NULL but does not cover @pfn the reference to it while be released. */ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, struct dev_pagemap *pgmap) { - const struct resource *res = pgmap ? pgmap->res : NULL; resource_size_t phys = PFN_PHYS(pfn); /* - * In the cached case we're already holding a live reference so - * we can simply do a blind increment + * In the cached case we're already holding a live reference. */ - if (res && phys >= res->start && phys <= res->end) { - percpu_ref_get(pgmap->ref); - return pgmap; + if (pgmap) { + const struct resource *res = pgmap ? pgmap->res : NULL; + + if (res && phys >= res->start && phys <= res->end) + return pgmap; + put_dev_pagemap(pgmap); } /* fall back to slow path lookup */ diff --git a/mm/gup.c b/mm/gup.c index d3fb60e5bfac..9d142eb9e2e9 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1410,7 +1410,6 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON_PAGE(compound_head(page) != head, page); - put_dev_pagemap(pgmap); SetPageReferenced(page); pages[*nr] = page; (*nr)++; @@ -1420,6 +1419,8 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, ret = 1; pte_unmap: + if (pgmap) + put_dev_pagemap(pgmap); pte_unmap(ptem); return ret; } @@ -1459,10 +1460,12 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr, SetPageReferenced(page); pages[*nr] = page; get_page(page); - put_dev_pagemap(pgmap); (*nr)++; pfn++; } while (addr += PAGE_SIZE, addr != end); + + if (pgmap) + put_dev_pagemap(pgmap); return 1; } -- 2.14.2