From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Al Viro" <viro@zeniv.linux.org.uk>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Dave Chinner" <david@fromorbit.com>,
"David Airlie" <airlied@linux.ie>,
"David S . Miller" <davem@davemloft.net>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>, "Jens Axboe" <axboe@kernel.dk>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Paul Mackerras" <paulus@samba.org>,
"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
bpf@vger.kernel.org, dri-devel@lists.freedesktop.org,
kvm@vger.kernel.org, linux-block@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org,
linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
netdev@vger.kernel.org, linux-mm@kvack.org,
LKML <linux-kernel@vger.kernel.org>,
"John Hubbard" <jhubbard@nvidia.com>
Subject: [PATCH v4 04/23] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages
Date: Tue, 12 Nov 2019 20:26:51 -0800 [thread overview]
Message-ID: <20191113042710.3997854-5-jhubbard@nvidia.com> (raw)
In-Reply-To: <20191113042710.3997854-1-jhubbard@nvidia.com>
An upcoming patch changes and complicates the refcounting and
especially the "put page" aspects of it. In order to keep
everything clean, refactor the devmap page release routines:
* Rename put_devmap_managed_page() to page_is_devmap_managed(),
and limit the functionality to "read only": return a bool,
with no side effects.
* Add a new routine, put_devmap_managed_page(), to handle checking
what kind of page it is, and what kind of refcount handling it
requires.
* Rename __put_devmap_managed_page() to free_devmap_managed_page(),
and limit the functionality to unconditionally freeing a devmap
page.
This is originally based on a separate patch by Ira Weiny, which
applied to an early version of the put_user_page() experiments.
Since then, Jérôme Glisse suggested the refactoring described above.
Suggested-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
include/linux/mm.h | 27 ++++++++++++++++---
mm/memremap.c | 67 ++++++++++++++++++++--------------------------
2 files changed, 53 insertions(+), 41 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a2adf95b3f9c..96228376139c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -967,9 +967,10 @@ static inline bool is_zone_device_page(const struct page *page)
#endif
#ifdef CONFIG_DEV_PAGEMAP_OPS
-void __put_devmap_managed_page(struct page *page);
+void free_devmap_managed_page(struct page *page);
DECLARE_STATIC_KEY_FALSE(devmap_managed_key);
-static inline bool put_devmap_managed_page(struct page *page)
+
+static inline bool page_is_devmap_managed(struct page *page)
{
if (!static_branch_unlikely(&devmap_managed_key))
return false;
@@ -978,7 +979,6 @@ static inline bool put_devmap_managed_page(struct page *page)
switch (page->pgmap->type) {
case MEMORY_DEVICE_PRIVATE:
case MEMORY_DEVICE_FS_DAX:
- __put_devmap_managed_page(page);
return true;
default:
break;
@@ -986,6 +986,27 @@ static inline bool put_devmap_managed_page(struct page *page)
return false;
}
+static inline bool put_devmap_managed_page(struct page *page)
+{
+ bool is_devmap = page_is_devmap_managed(page);
+
+ if (is_devmap) {
+ int count = page_ref_dec_return(page);
+
+ /*
+ * devmap page refcounts are 1-based, rather than 0-based: if
+ * refcount is 1, then the page is free and the refcount is
+ * stable because nobody holds a reference on the page.
+ */
+ if (count == 1)
+ free_devmap_managed_page(page);
+ else if (!count)
+ __put_page(page);
+ }
+
+ return is_devmap;
+}
+
#else /* CONFIG_DEV_PAGEMAP_OPS */
static inline bool put_devmap_managed_page(struct page *page)
{
diff --git a/mm/memremap.c b/mm/memremap.c
index 03ccbdfeb697..bc7e2a27d025 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -410,48 +410,39 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
EXPORT_SYMBOL_GPL(get_dev_pagemap);
#ifdef CONFIG_DEV_PAGEMAP_OPS
-void __put_devmap_managed_page(struct page *page)
+void free_devmap_managed_page(struct page *page)
{
- int count = page_ref_dec_return(page);
+ /* Clear Active bit in case of parallel mark_page_accessed */
+ __ClearPageActive(page);
+ __ClearPageWaiters(page);
+
+ mem_cgroup_uncharge(page);
/*
- * If refcount is 1 then page is freed and refcount is stable as nobody
- * holds a reference on the 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.
*/
- if (count == 1) {
- /* 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.
- */
- if (is_device_private_page(page))
- page->mapping = NULL;
+ if (is_device_private_page(page))
+ page->mapping = NULL;
- page->pgmap->ops->page_free(page);
- } else if (!count)
- __put_page(page);
+ page->pgmap->ops->page_free(page);
}
-EXPORT_SYMBOL(__put_devmap_managed_page);
+EXPORT_SYMBOL(free_devmap_managed_page);
#endif /* CONFIG_DEV_PAGEMAP_OPS */
--
2.24.0
next prev parent reply other threads:[~2019-11-13 4:31 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-13 4:26 [PATCH v4 00/23] mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM John Hubbard
2019-11-13 4:26 ` [PATCH v4 01/23] mm/gup: pass flags arg to __gup_device_* functions John Hubbard
2019-11-13 10:50 ` Jan Kara
2019-11-13 4:26 ` [PATCH v4 02/23] mm/gup: factor out duplicate code from four routines John Hubbard
2019-11-13 11:15 ` Jan Kara
2019-11-13 23:12 ` John Hubbard
2019-11-13 4:26 ` [PATCH v4 03/23] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-11-13 10:50 ` Jan Kara
2019-11-13 18:38 ` Ira Weiny
2019-11-13 4:26 ` John Hubbard [this message]
2019-11-13 10:49 ` [PATCH v4 04/23] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages Jan Kara
2019-11-13 19:09 ` Jerome Glisse
2019-11-13 19:23 ` Dan Williams
2019-11-13 22:00 ` Dan Williams
2019-11-13 22:46 ` John Hubbard
2019-11-13 22:55 ` Dan Williams
2019-11-13 22:56 ` John Hubbard
2019-11-13 23:03 ` Jerome Glisse
2019-11-13 4:26 ` [PATCH v4 05/23] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-11-13 4:26 ` [PATCH v4 06/23] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-11-13 4:26 ` [PATCH v4 07/23] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-11-13 4:26 ` [PATCH v4 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM John Hubbard
2019-11-13 13:02 ` Jason Gunthorpe
2019-11-13 19:17 ` Ira Weiny
2019-11-13 20:19 ` John Hubbard
2019-11-13 18:47 ` Ira Weiny
2019-11-13 4:26 ` [PATCH v4 09/23] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-11-13 10:43 ` Jan Kara
2019-11-13 18:31 ` Ira Weiny
2019-11-13 18:45 ` Dan Williams
2019-11-13 23:22 ` John Hubbard
2019-11-14 6:08 ` John Hubbard
2019-11-13 18:59 ` Ira Weiny
2019-11-13 20:24 ` John Hubbard
2019-11-13 4:26 ` [PATCH v4 10/23] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-13 4:26 ` [PATCH v4 11/23] IB/{core,hw,umem}: set FOLL_PIN, FOLL_LONGTERM via pin_longterm_pages*() John Hubbard
2019-11-13 4:26 ` [PATCH v4 12/23] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-11-13 4:27 ` [PATCH v4 13/23] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-11-13 4:27 ` [PATCH v4 14/23] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-11-13 4:27 ` [PATCH v4 15/23] net/xdp: " John Hubbard
2019-11-13 4:27 ` [PATCH v4 16/23] mm/gup: track FOLL_PIN pages John Hubbard
2019-11-13 4:27 ` [PATCH v4 17/23] media/v4l2-core: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-11-13 4:27 ` [PATCH v4 18/23] vfio, mm: " John Hubbard
2019-11-13 4:27 ` [PATCH v4 19/23] powerpc: book3s64: convert to pin_longterm_pages() and put_user_page() John Hubbard
2019-11-13 4:27 ` [PATCH v4 20/23] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-11-13 19:01 ` Ira Weiny
2019-11-13 4:27 ` [PATCH v4 21/23] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-11-13 19:03 ` Ira Weiny
2019-11-13 4:27 ` [PATCH v4 22/23] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-11-13 19:06 ` Ira Weiny
2019-11-13 4:27 ` [PATCH v4 23/23] mm/gup: remove support for gup(FOLL_LONGTERM) John Hubbard
2019-11-13 19:09 ` Ira Weiny
2019-11-13 23:27 ` John Hubbard
2019-11-13 4:32 ` [PATCH v4 00/23] mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM John Hubbard
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