diff options
| author | John Hubbard <jhubbard@nvidia.com> | 2020-01-30 22:12:28 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-01-31 10:30:37 -0800 |
| commit | 07d8026995287c2a2f03e28c69cdd8152fa69107 (patch) | |
| tree | 394576c123fb32b37b232dce66fbdf87a36f3bcf /mm/swap.c | |
| parent | 429589d647c1adc80b32645fbb8852689525d9cd (diff) | |
| download | linux-07d8026995287c2a2f03e28c69cdd8152fa69107.tar.bz2 | |
mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages
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 decrementing
the refcount for ZONE_DEVICE pages.
* Change callers (just release_pages() and put_page()) to check
page_is_devmap_managed() before calling the new
put_devmap_managed_page() routine. This is a performance point:
put_page() is a hot path, so we need to avoid non- inline function calls
where possible.
* 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.
Link: http://lkml.kernel.org/r/20200107224558.2362728-5-jhubbard@nvidia.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Suggested-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
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: 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>
Diffstat (limited to 'mm/swap.c')
| -rw-r--r-- | mm/swap.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/mm/swap.c b/mm/swap.c index 5341ae93861f..cf39d24ada2a 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -813,8 +813,10 @@ void release_pages(struct page **pages, int nr) * processing, and instead, expect a call to * put_page_testzero(). */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); continue; + } } page = compound_head(page); @@ -1102,3 +1104,26 @@ void __init swap_setup(void) * _really_ don't want to cluster much more */ } + +#ifdef CONFIG_DEV_PAGEMAP_OPS +void put_devmap_managed_page(struct page *page) +{ + int count; + + if (WARN_ON_ONCE(!page_is_devmap_managed(page))) + return; + + 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); +} +EXPORT_SYMBOL(put_devmap_managed_page); +#endif |