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author | John Hubbard <jhubbard@nvidia.com> | 2020-01-30 22:12:28 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-01-31 10:30:37 -0800 |
commit | 07d8026995287c2a2f03e28c69cdd8152fa69107 (patch) | |
tree | 394576c123fb32b37b232dce66fbdf87a36f3bcf | |
parent | 429589d647c1adc80b32645fbb8852689525d9cd (diff) | |
download | linux-07d8026995287c2a2f03e28c69cdd8152fa69107.tar.gz linux-07d8026995287c2a2f03e28c69cdd8152fa69107.tar.bz2 linux-07d8026995287c2a2f03e28c69cdd8152fa69107.zip |
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>
-rw-r--r-- | include/linux/mm.h | 18 | ||||
-rw-r--r-- | mm/memremap.c | 15 | ||||
-rw-r--r-- | mm/swap.c | 27 |
3 files changed, 40 insertions, 20 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 1233bf45164d..3b88618e361a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -947,9 +947,10 @@ static inline bool is_zone_device_page(const struct page *page) #endif #ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page); +void free_devmap_managed_page(struct page *page); DECLARE_STATIC_KEY_FALSE(devmap_managed_key); -static inline bool put_devmap_managed_page(struct page *page) + +static inline bool page_is_devmap_managed(struct page *page) { if (!static_branch_unlikely(&devmap_managed_key)) return false; @@ -958,7 +959,6 @@ static inline bool put_devmap_managed_page(struct page *page) switch (page->pgmap->type) { case MEMORY_DEVICE_PRIVATE: case MEMORY_DEVICE_FS_DAX: - __put_devmap_managed_page(page); return true; default: break; @@ -966,11 +966,17 @@ static inline bool put_devmap_managed_page(struct page *page) return false; } +void put_devmap_managed_page(struct page *page); + #else /* CONFIG_DEV_PAGEMAP_OPS */ -static inline bool put_devmap_managed_page(struct page *page) +static inline bool page_is_devmap_managed(struct page *page) { return false; } + +static inline void put_devmap_managed_page(struct page *page) +{ +} #endif /* CONFIG_DEV_PAGEMAP_OPS */ static inline bool is_device_private_page(const struct page *page) @@ -1023,8 +1029,10 @@ static inline void put_page(struct page *page) * need to inform the device driver through callback. See * include/linux/memremap.h and HMM for details. */ - if (put_devmap_managed_page(page)) + if (page_is_devmap_managed(page)) { + put_devmap_managed_page(page); return; + } if (put_page_testzero(page)) __put_page(page); diff --git a/mm/memremap.c b/mm/memremap.c index f915d074ac20..4c723d2049d5 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -411,20 +411,8 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn, EXPORT_SYMBOL_GPL(get_dev_pagemap); #ifdef CONFIG_DEV_PAGEMAP_OPS -void __put_devmap_managed_page(struct page *page) +void free_devmap_managed_page(struct page *page) { - int count = page_ref_dec_return(page); - - /* still busy */ - if (count > 1) - return; - - /* 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); @@ -461,5 +449,4 @@ void __put_devmap_managed_page(struct page *page) page->mapping = NULL; page->pgmap->ops->page_free(page); } -EXPORT_SYMBOL(__put_devmap_managed_page); #endif /* CONFIG_DEV_PAGEMAP_OPS */ 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 |