From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 026/118] mm: Cleanup __put_devmap_managed_page() vs ->page_free() Date: Thu, 30 Jan 2020 22:12:24 -0800 Message-ID: <20200131061224.QNkOo1KS6%akpm@linux-foundation.org> References: <20200130221021.5f0211c56346d5485af07923@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Return-path: Received: from mail.kernel.org ([198.145.29.99]:59500 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725907AbgAaGM1 (ORCPT ); Fri, 31 Jan 2020 01:12:27 -0500 In-Reply-To: <20200130221021.5f0211c56346d5485af07923@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, alex.williamson@redhat.com, aneesh.kumar@linux.ibm.com, axboe@kernel.dk, bjorn.topel@intel.com, corbet@lwn.net, dan.j.williams@intel.com, daniel.vetter@ffwll.ch, hch@lst.de, hverkuil-cisco@xs4all.nl, ira.weiny@intel.com, jack@suse.cz, jgg@mellanox.com, jgg@ziepe.ca, jglisse@redhat.com, jhubbard@nvidia.com, kirill@shutemov.name, leonro@mellanox.com, linux-mm@kvack.org, mchehab@kernel.org, mm-commits@vger.kernel.org, rppt@linux.ibm.com, torvalds@linux-foundation.org =46rom: Dan Williams Subject: mm: Cleanup __put_devmap_managed_page() vs ->page_free() After the removal of the device-public infrastructure there are only 2 ->page_free() call backs in the kernel. One of those is a device-private callback in the nouveau driver, the other is a generic wakeup needed in the DAX case. In the hopes that all ->page_free() callbacks can be migrated to common core kernel functionality, move the device-private specific actions in __put_devmap_managed_page() under the is_device_private_page() conditional, including the ->page_free() callback. For the other page types just open-code the generic wakeup. Yes, the wakeup is only needed in the MEMORY_DEVICE_FSDAX case, but it does no harm in the MEMORY_DEVICE_DEVDAX and MEMORY_DEVICE_PCI_P2PDMA case. Link: http://lkml.kernel.org/r/20200107224558.2362728-4-jhubbard@nvidia.com Signed-off-by: Dan Williams Signed-off-by: John Hubbard Reviewed-by: Christoph Hellwig Reviewed-by: J=C3=A9r=C3=B4me Glisse Cc: Jan Kara Cc: Ira Weiny Cc: Alex Williamson Cc: Aneesh Kumar K.V Cc: Bj=C3=B6rn T=C3=B6pel Cc: Daniel Vetter Cc: Hans Verkuil Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: Jens Axboe Cc: Jonathan Corbet Cc: Kirill A. Shutemov Cc: Leon Romanovsky Cc: Mauro Carvalho Chehab Cc: Mike Rapoport Signed-off-by: Andrew Morton --- drivers/nvdimm/pmem.c | 6 --- mm/memremap.c | 80 ++++++++++++++++++++++------------------ 2 files changed, 44 insertions(+), 42 deletions(-) --- a/drivers/nvdimm/pmem.c~mm-cleanup-__put_devmap_managed_page-vs-page_fr= ee +++ a/drivers/nvdimm/pmem.c @@ -337,13 +337,7 @@ static void pmem_release_disk(void *__pm put_disk(pmem->disk); } =20 -static void pmem_pagemap_page_free(struct page *page) -{ - wake_up_var(&page->_refcount); -} - static const struct dev_pagemap_ops fsdax_pagemap_ops =3D { - .page_free =3D pmem_pagemap_page_free, .kill =3D pmem_pagemap_kill, .cleanup =3D pmem_pagemap_cleanup, }; --- a/mm/memremap.c~mm-cleanup-__put_devmap_managed_page-vs-page_free +++ a/mm/memremap.c @@ -27,7 +27,8 @@ static void devmap_managed_enable_put(vo =20 static int devmap_managed_enable_get(struct dev_pagemap *pgmap) { - if (!pgmap->ops || !pgmap->ops->page_free) { + if (pgmap->type =3D=3D MEMORY_DEVICE_PRIVATE && + (!pgmap->ops || !pgmap->ops->page_free)) { WARN(1, "Missing page_free method\n"); return -EINVAL; } @@ -414,44 +415,51 @@ void __put_devmap_managed_page(struct pa { int count =3D page_ref_dec_return(page); =20 - /* - * If refcount is 1 then page is freed and refcount is stable as nobody - * holds a reference on the page. - */ - if (count =3D=3D 1) { - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); - __ClearPageWaiters(page); + /* still busy */ + if (count > 1) + return; =20 - mem_cgroup_uncharge(page); + /* only triggered by the dev_pagemap shutdown path */ + if (count =3D=3D 0) { + __put_page(page); + return; + } =20 - /* - * When a device_private page is freed, the page->mapping field - * may still contain a (stale) mapping value. For example, the - * lower bits of page->mapping may still identify the page as - * an anonymous page. Ultimately, this entire field is just - * stale and wrong, and it will cause errors if not cleared. - * One example is: - * - * migrate_vma_pages() - * migrate_vma_insert_page() - * page_add_new_anon_rmap() - * __page_set_anon_rmap() - * ...checks page->mapping, via PageAnon(page) call, - * and incorrectly concludes that the page is an - * anonymous page. Therefore, it incorrectly, - * silently fails to set up the new anon rmap. - * - * For other types of ZONE_DEVICE pages, migration is either - * handled differently or not done at all, so there is no need - * to clear page->mapping. - */ - if (is_device_private_page(page)) - page->mapping =3D NULL; + /* notify page idle for dax */ + if (!is_device_private_page(page)) { + wake_up_var(&page->_refcount); + return; + } =20 - page->pgmap->ops->page_free(page); - } else if (!count) - __put_page(page); + /* Clear Active bit in case of parallel mark_page_accessed */ + __ClearPageActive(page); + __ClearPageWaiters(page); + + mem_cgroup_uncharge(page); + + /* + * When a device_private page is freed, the page->mapping field + * may still contain a (stale) mapping value. For example, the + * lower bits of page->mapping may still identify the page as an + * anonymous page. Ultimately, this entire field is just stale + * and wrong, and it will cause errors if not cleared. One + * example is: + * + * migrate_vma_pages() + * migrate_vma_insert_page() + * page_add_new_anon_rmap() + * __page_set_anon_rmap() + * ...checks page->mapping, via PageAnon(page) call, + * and incorrectly concludes that the page is an + * anonymous page. Therefore, it incorrectly, + * silently fails to set up the new anon rmap. + * + * For other types of ZONE_DEVICE pages, migration is either + * handled differently or not done at all, so there is no need + * to clear page->mapping. + */ + page->mapping =3D NULL; + page->pgmap->ops->page_free(page); } EXPORT_SYMBOL(__put_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */ _