![Hugh Dickins](/assets/img/avatar_default.png)
Though debug kernels have a VM_BUG_ON to help protect from misaccounting lru_size, non-debug kernels are liable to wrap it around: and then the vast unsigned long size draws page reclaim into a loop of repeatedly doing nothing on an empty list, without even a cond_resched(). That soft lockup looks confusingly like an over-busy reclaim scenario, with lots of contention on the lru_lock in shrink_inactive_list(): yet has a totally different origin. Help differentiate with a custom warning in mem_cgroup_update_lru_size(), even in non-debug kernels; and reset the size to avoid the lockup. But the particular bug which suggested this change was mine alone, and since fixed. Make it a WARN_ONCE: the first occurrence is the most informative, a flurry may follow, yet even when rate-limited little more is learnt. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andres Lagar-Cavilla <andreslc@google.com> Cc: Yang Shi <yang.shi@linaro.org> Cc: Ning Qu <quning@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Andres Lagar-Cavilla <andreslc@google.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
106 lines
2.8 KiB
C
106 lines
2.8 KiB
C
#ifndef LINUX_MM_INLINE_H
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#define LINUX_MM_INLINE_H
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#include <linux/huge_mm.h>
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#include <linux/swap.h>
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/**
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* page_is_file_cache - should the page be on a file LRU or anon LRU?
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* @page: the page to test
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*
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* Returns 1 if @page is page cache page backed by a regular filesystem,
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* or 0 if @page is anonymous, tmpfs or otherwise ram or swap backed.
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* Used by functions that manipulate the LRU lists, to sort a page
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* onto the right LRU list.
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*
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* We would like to get this info without a page flag, but the state
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* needs to survive until the page is last deleted from the LRU, which
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* could be as far down as __page_cache_release.
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*/
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static inline int page_is_file_cache(struct page *page)
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{
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return !PageSwapBacked(page);
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}
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static __always_inline void add_page_to_lru_list(struct page *page,
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struct lruvec *lruvec, enum lru_list lru)
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{
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int nr_pages = hpage_nr_pages(page);
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mem_cgroup_update_lru_size(lruvec, lru, nr_pages);
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list_add(&page->lru, &lruvec->lists[lru]);
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__mod_zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru, nr_pages);
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}
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static __always_inline void del_page_from_lru_list(struct page *page,
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struct lruvec *lruvec, enum lru_list lru)
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{
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int nr_pages = hpage_nr_pages(page);
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list_del(&page->lru);
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mem_cgroup_update_lru_size(lruvec, lru, -nr_pages);
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__mod_zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru, -nr_pages);
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}
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/**
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* page_lru_base_type - which LRU list type should a page be on?
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* @page: the page to test
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*
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* Used for LRU list index arithmetic.
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*
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* Returns the base LRU type - file or anon - @page should be on.
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*/
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static inline enum lru_list page_lru_base_type(struct page *page)
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{
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if (page_is_file_cache(page))
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return LRU_INACTIVE_FILE;
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return LRU_INACTIVE_ANON;
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}
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/**
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* page_off_lru - which LRU list was page on? clearing its lru flags.
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* @page: the page to test
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*
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* Returns the LRU list a page was on, as an index into the array of LRU
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* lists; and clears its Unevictable or Active flags, ready for freeing.
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*/
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static __always_inline enum lru_list page_off_lru(struct page *page)
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{
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enum lru_list lru;
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if (PageUnevictable(page)) {
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__ClearPageUnevictable(page);
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lru = LRU_UNEVICTABLE;
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} else {
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lru = page_lru_base_type(page);
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if (PageActive(page)) {
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__ClearPageActive(page);
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lru += LRU_ACTIVE;
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}
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}
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return lru;
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}
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/**
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* page_lru - which LRU list should a page be on?
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* @page: the page to test
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*
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* Returns the LRU list a page should be on, as an index
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* into the array of LRU lists.
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*/
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static __always_inline enum lru_list page_lru(struct page *page)
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{
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enum lru_list lru;
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if (PageUnevictable(page))
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lru = LRU_UNEVICTABLE;
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else {
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lru = page_lru_base_type(page);
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if (PageActive(page))
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lru += LRU_ACTIVE;
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}
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return lru;
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}
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#define lru_to_page(head) (list_entry((head)->prev, struct page, lru))
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#endif
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