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 <dan.j.williams@intel.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jérôme Glisse <jglisse@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Björn Töpel <bjorn.topel@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: Jason Gunthorpe <jgg@mellanox.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Leon Romanovsky <leonro@mellanox.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -337,13 +337,7 @@ static void pmem_release_disk(void *__pmem)
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put_disk(pmem->disk);
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}
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static void pmem_pagemap_page_free(struct page *page)
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{
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wake_up_var(&page->_refcount);
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}
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static const struct dev_pagemap_ops fsdax_pagemap_ops = {
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.page_free = pmem_pagemap_page_free,
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.kill = pmem_pagemap_kill,
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.cleanup = pmem_pagemap_cleanup,
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};
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@ -27,7 +27,8 @@ static void devmap_managed_enable_put(void)
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static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
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{
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if (!pgmap->ops || !pgmap->ops->page_free) {
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if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
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(!pgmap->ops || !pgmap->ops->page_free)) {
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WARN(1, "Missing page_free method\n");
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return -EINVAL;
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}
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@ -414,44 +415,51 @@ void __put_devmap_managed_page(struct page *page)
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{
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int count = page_ref_dec_return(page);
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/*
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* If refcount is 1 then page is freed and refcount is stable as nobody
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* holds a reference on the page.
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*/
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if (count == 1) {
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/* Clear Active bit in case of parallel mark_page_accessed */
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__ClearPageActive(page);
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__ClearPageWaiters(page);
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/* still busy */
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if (count > 1)
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return;
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mem_cgroup_uncharge(page);
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/*
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* When a device_private page is freed, the page->mapping field
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* may still contain a (stale) mapping value. For example, the
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* lower bits of page->mapping may still identify the page as
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* an anonymous page. Ultimately, this entire field is just
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* stale and wrong, and it will cause errors if not cleared.
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* One example is:
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*
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* migrate_vma_pages()
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* migrate_vma_insert_page()
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* page_add_new_anon_rmap()
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* __page_set_anon_rmap()
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* ...checks page->mapping, via PageAnon(page) call,
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* and incorrectly concludes that the page is an
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* anonymous page. Therefore, it incorrectly,
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* silently fails to set up the new anon rmap.
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*
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* For other types of ZONE_DEVICE pages, migration is either
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* handled differently or not done at all, so there is no need
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* to clear page->mapping.
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*/
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if (is_device_private_page(page))
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page->mapping = NULL;
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page->pgmap->ops->page_free(page);
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} else if (!count)
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/* only triggered by the dev_pagemap shutdown path */
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if (count == 0) {
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__put_page(page);
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return;
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}
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/* notify page idle for dax */
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if (!is_device_private_page(page)) {
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wake_up_var(&page->_refcount);
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return;
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}
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/* Clear Active bit in case of parallel mark_page_accessed */
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__ClearPageActive(page);
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__ClearPageWaiters(page);
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mem_cgroup_uncharge(page);
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/*
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* When a device_private page is freed, the page->mapping field
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* may still contain a (stale) mapping value. For example, the
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* lower bits of page->mapping may still identify the page as an
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* anonymous page. Ultimately, this entire field is just stale
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* and wrong, and it will cause errors if not cleared. One
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* example is:
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*
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* migrate_vma_pages()
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* migrate_vma_insert_page()
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* page_add_new_anon_rmap()
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* __page_set_anon_rmap()
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* ...checks page->mapping, via PageAnon(page) call,
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* and incorrectly concludes that the page is an
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* anonymous page. Therefore, it incorrectly,
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* silently fails to set up the new anon rmap.
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*
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* For other types of ZONE_DEVICE pages, migration is either
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* handled differently or not done at all, so there is no need
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* to clear page->mapping.
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*/
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page->mapping = NULL;
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page->pgmap->ops->page_free(page);
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}
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EXPORT_SYMBOL(__put_devmap_managed_page);
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#endif /* CONFIG_DEV_PAGEMAP_OPS */
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