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mm: use a dedicated lock to protect totalram_pages and zone->managed_pages
Currently lock_memory_hotplug()/unlock_memory_hotplug() are used to protect totalram_pages and zone->managed_pages. Other than the memory hotplug driver, totalram_pages and zone->managed_pages may also be modified at runtime by other drivers, such as Xen balloon, virtio_balloon etc. For those cases, memory hotplug lock is a little too heavy, so introduce a dedicated lock to protect totalram_pages and zone->managed_pages. Now we have a simplified locking rules totalram_pages and zone->managed_pages as: 1) no locking for read accesses because they are unsigned long. 2) no locking for write accesses at boot time in single-threaded context. 3) serialize write accesses at runtime by acquiring the dedicated managed_page_count_lock. Also adjust zone->managed_pages when freeing reserved pages into the buddy system, to keep totalram_pages and zone->managed_pages in consistence. [akpm@linux-foundation.org: don't export adjust_managed_page_count to modules (for now)] Signed-off-by: Jiang Liu <jiang.liu@huawei.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Michel Lespinasse <walken@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: <sworddragon2@aol.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: David Howells <dhowells@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Joonsoo Kim <js1304@gmail.com> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Tang Chen <tangchen@cn.fujitsu.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wen Congyang <wency@cn.fujitsu.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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3 changed files with 23 additions and 8 deletions
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@ -1313,6 +1313,7 @@ extern void free_initmem(void);
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*/
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extern unsigned long free_reserved_area(void *start, void *end,
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int poison, char *s);
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#ifdef CONFIG_HIGHMEM
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/*
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* Free a highmem page into the buddy system, adjusting totalhigh_pages
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@ -1321,10 +1322,7 @@ extern unsigned long free_reserved_area(void *start, void *end,
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extern void free_highmem_page(struct page *page);
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#endif
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static inline void adjust_managed_page_count(struct page *page, long count)
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{
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totalram_pages += count;
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}
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extern void adjust_managed_page_count(struct page *page, long count);
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/* Free the reserved page into the buddy system, so it gets managed. */
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static inline void __free_reserved_page(struct page *page)
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@ -474,10 +474,16 @@ struct zone {
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* frequently read in proximity to zone->lock. It's good to
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* give them a chance of being in the same cacheline.
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*
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* Write access to present_pages and managed_pages at runtime should
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* be protected by lock_memory_hotplug()/unlock_memory_hotplug().
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* Any reader who can't tolerant drift of present_pages and
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* managed_pages should hold memory hotplug lock to get a stable value.
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* Write access to present_pages at runtime should be protected by
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* lock_memory_hotplug()/unlock_memory_hotplug(). Any reader who can't
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* tolerant drift of present_pages should hold memory hotplug lock to
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* get a stable value.
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*
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* Read access to managed_pages should be safe because it's unsigned
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* long. Write access to zone->managed_pages and totalram_pages are
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* protected by managed_page_count_lock at runtime. Idealy only
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* adjust_managed_page_count() should be used instead of directly
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* touching zone->managed_pages and totalram_pages.
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*/
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unsigned long spanned_pages;
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unsigned long present_pages;
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@ -103,6 +103,9 @@ nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
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};
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EXPORT_SYMBOL(node_states);
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/* Protect totalram_pages and zone->managed_pages */
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static DEFINE_SPINLOCK(managed_page_count_lock);
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unsigned long totalram_pages __read_mostly;
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unsigned long totalreserve_pages __read_mostly;
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/*
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@ -5206,6 +5209,14 @@ early_param("movablecore", cmdline_parse_movablecore);
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#endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
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void adjust_managed_page_count(struct page *page, long count)
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{
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spin_lock(&managed_page_count_lock);
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page_zone(page)->managed_pages += count;
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totalram_pages += count;
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spin_unlock(&managed_page_count_lock);
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}
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unsigned long free_reserved_area(void *start, void *end, int poison, char *s)
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{
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void *pos;
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