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mm: Cleanup __put_devmap_managed_page() vs ->page_free()

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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>
This commit is contained in:
Dan Williams 2020-01-30 22:12:24 -08:00 committed by Linus Torvalds
parent a707cdd55f
commit 429589d647
2 changed files with 45 additions and 43 deletions
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6
drivers/nvdimm/pmem.c
View File

@ -337,13 +337,7 @@ static void pmem_release_disk(void *__pmem)
put_disk(pmem->disk);
}
static void pmem_pagemap_page_free(struct page *page)
{
wake_up_var(&page->_refcount);
}
static const struct dev_pagemap_ops fsdax_pagemap_ops = {
.page_free = pmem_pagemap_page_free,
.kill = pmem_pagemap_kill,
.cleanup = pmem_pagemap_cleanup,
};

82
mm/memremap.c
View File

@ -27,7 +27,8 @@ static void devmap_managed_enable_put(void)
static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
if (!pgmap->ops || !pgmap->ops->page_free) {
if (pgmap->type == 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 page *page)
{
int count = page_ref_dec_return(page);
/*
* If refcount is 1 then page is freed and refcount is stable as nobody
* holds a reference on the page.
*/
if (count == 1) {
/* Clear Active bit in case of parallel mark_page_accessed */
__ClearPageActive(page);
__ClearPageWaiters(page);
/* still busy */
if (count > 1)
return;
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;
page->pgmap->ops->page_free(page);
} else if (!count)
/* only triggered by the dev_pagemap shutdown path */
if (count == 0) {
__put_page(page);
return;
}
/* notify page idle for dax */
if (!is_device_private_page(page)) {
wake_up_var(&page->_refcount);
return;
}
/* 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 = NULL;
page->pgmap->ops->page_free(page);
}
EXPORT_SYMBOL(__put_devmap_managed_page);
#endif /* CONFIG_DEV_PAGEMAP_OPS */