Messages in this thread Patch in this message | | | Date | Mon, 6 Sep 2010 14:42:28 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [BUGFIX][PATCH 1/3] memory hotplug: fix next block calculation in is_removable |
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From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
next_active_pageblock() is for finding next _used_ freeblock. It skips several blocks when it finds there are a chunk of free pages lager than pageblock. But it has 2 bugs.
1. We have no lock. page_order(page) - pageblock_order can be minus. 2. pageblocks_stride += is wrong. it should skip page_order(p) of pages.
CC: stable@kernel.org Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memory_hotplug.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
Index: kametest/mm/memory_hotplug.c =================================================================== --- kametest.orig/mm/memory_hotplug.c +++ kametest/mm/memory_hotplug.c @@ -584,19 +584,19 @@ static inline int pageblock_free(struct /* Return the start of the next active pageblock after a given page */ static struct page *next_active_pageblock(struct page *page) { - int pageblocks_stride; - /* Ensure the starting page is pageblock-aligned */ BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); - /* Move forward by at least 1 * pageblock_nr_pages */ - pageblocks_stride = 1; - /* If the entire pageblock is free, move to the end of free page */ - if (pageblock_free(page)) - pageblocks_stride += page_order(page) - pageblock_order; + if (pageblock_free(page)) { + int order; + /* be careful. we don't have locks, page_order can be changed.*/ + order = page_order(page); + if (order > pageblock_order) + return page + (1 << order); + } - return page + (pageblocks_stride * pageblock_nr_pages); + return page + pageblock_nr_pages; } /* Checks if this range of memory is likely to be hot-removable. */
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