The patch titled Subject: mm: document zone device struct page field usage has been added to the -mm tree. Its filename is mm-document-zone-device-struct-page-field-usage.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-document-zone-device-struct-page... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-document-zone-device-struct-page...
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated there every 3-4 working days
------------------------------------------------------ From: Ralph Campbell rcampbell@nvidia.com Subject: mm: document zone device struct page field usage
Struct page for ZONE_DEVICE private pages uses the page->mapping and and page->index fields while the source anonymous pages are migrated to device private memory. This is so rmap_walk() can find the page when migrating the ZONE_DEVICE private page back to system memory. ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and page->index fields when files are mapped into a process address space.
Restructure struct page and add comments to make this more clear.
Link: http://lkml.kernel.org/r/20190719192955.30462-2-rcampbell@nvidia.com Signed-off-by: Ralph Campbell rcampbell@nvidia.com Reviewed-by: John Hubbard jhubbard@nvidia.com Cc: Matthew Wilcox willy@infradead.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Christoph Lameter cl@linux.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Jérôme Glisse jglisse@redhat.com Cc: "Kirill A . Shutemov" kirill.shutemov@linux.intel.com Cc: Lai Jiangshan jiangshanlai@gmail.com Cc: Martin Schwidefsky schwidefsky@de.ibm.com Cc: Pekka Enberg penberg@kernel.org Cc: Randy Dunlap rdunlap@infradead.org Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Christoph Hellwig hch@lst.de Cc: Jason Gunthorpe jgg@mellanox.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Dan Williams dan.j.williams@intel.com Cc: Ira Weiny ira.weiny@intel.com Cc: Jan Kara jack@suse.cz Cc: Logan Gunthorpe logang@deltatee.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@suse.com Cc: Mike Kravetz mike.kravetz@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/mm_types.h | 42 +++++++++++++++++++++++++------------ 1 file changed, 29 insertions(+), 13 deletions(-)
--- a/include/linux/mm_types.h~mm-document-zone-device-struct-page-field-usage +++ a/include/linux/mm_types.h @@ -76,13 +76,35 @@ struct page { * avoid collision and false-positive PageTail(). */ union { - struct { /* Page cache and anonymous pages */ - /** - * @lru: Pageout list, eg. active_list protected by - * pgdat->lru_lock. Sometimes used as a generic list - * by the page owner. - */ - struct list_head lru; + struct { /* Page cache, anonymous, ZONE_DEVICE pages */ + union { + /** + * @lru: Pageout list, e.g., active_list + * protected by pgdat->lru_lock. Sometimes + * used as a generic list by the page owner. + */ + struct list_head lru; + /** + * ZONE_DEVICE pages are never on the lru + * list so they reuse the list space. + * ZONE_DEVICE private pages are counted as + * being mapped so the @mapping and @index + * fields are used while the page is migrated + * to device private memory. + * ZONE_DEVICE MEMORY_DEVICE_FS_DAX pages also + * use the @mapping and @index fields when pmem + * backed DAX files are mapped. + */ + struct { + /** + * @pgmap: Points to the hosting + * device page map. + */ + struct dev_pagemap *pgmap; + /** @zone_device_data: opaque data. */ + void *zone_device_data; + }; + }; /* See page-flags.h for PAGE_MAPPING_FLAGS */ struct address_space *mapping; pgoff_t index; /* Our offset within mapping. */ @@ -155,12 +177,6 @@ struct page { spinlock_t ptl; #endif }; - struct { /* ZONE_DEVICE pages */ - /** @pgmap: Points to the hosting device page map. */ - struct dev_pagemap *pgmap; - void *zone_device_data; - unsigned long _zd_pad_1; /* uses mapping */ - };
/** @rcu_head: You can use this to free a page by RCU. */ struct rcu_head rcu_head; _
Patches currently in -mm which might be from rcampbell@nvidia.com are
mm-document-zone-device-struct-page-field-usage.patch mm-hmm-fix-zone_device-anon-page-mapping-reuse.patch mm-hmm-fix-bad-subpage-pointer-in-try_to_unmap_one.patch