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mm: remove the extra ZONE_DEVICE struct page refcount

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ZONE_DEVICE struct pages have an extra reference count that complicates
the code for put_page() and several places in the kernel that need to
check the reference count to see that a page is not being used (gup,
compaction, migration, etc.). Clean up the code so the reference count
doesn't need to be treated specially for ZONE_DEVICE pages.

Note that this excludes the special idle page wakeup for fsdax pages,
which still happens at refcount 1.  This is a separate issue and will
be sorted out later.  Given that only fsdax pages require the
notifiacation when the refcount hits 1 now, the PAGEMAP_OPS Kconfig
symbol can go away and be replaced with a FS_DAX check for this hook
in the put_page fastpath.

Based on an earlier patch from Ralph Campbell <rcampbell@nvidia.com>.

Link: https://lkml.kernel.org/r/20220210072828.2930359-8-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Tested-by: "Sierra Guiza, Alejandro (Alex)" <alex.sierra@amd.com>

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Chaitanya Kulkarni <kch@nvidia.com>
Cc: Christian Knig <christian.koenig@amd.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Christoph Hellwig 2022-02-16 15:31:36 +11:00 • committed by Matthew Wilcox (Oracle)
parent dc90f0846d
commit 27674ef6c7
13 changed files with 36 additions and 83 deletions
Download patch file Download diff file Expand all files Collapse all files

16
mm/swap.c
View file

@ -122,17 +122,9 @@ static void __put_compound_page(struct page *page)
void __put_page(struct page *page)
{
if (is_zone_device_page(page)) {
put_dev_pagemap(page->pgmap);
/*
* The page belongs to the device that created pgmap. Do
* not return it to page allocator.
*/
return;
}
if (unlikely(PageCompound(page)))
if (unlikely(is_zone_device_page(page)))
free_zone_device_page(page);
else if (unlikely(PageCompound(page)))
__put_compound_page(page);
else
__put_single_page(page);
@ -933,7 +925,7 @@ void release_pages(struct page **pages, int nr)
if (put_devmap_managed_page(page))
continue;
if (put_page_testzero(page))
put_dev_pagemap(page->pgmap);
free_zone_device_page(page);
continue;
}