Commit ee0ea59cf9ea95369d686bdc4b3d8c027e2b99cd
Committed by
Linus Torvalds
Linus Torvalds
1 parent
e850dcf530
Exists in
master
and in
20 other branches
ksm: reorganize ksm_check_stable_tree
Memory hotremove's ksm_check_stable_tree() is pitifully inefficient (restarting whenever it finds a stale node to remove), but rearrange so that at least it does not needlessly restart from nid 0 each time. And add a couple of comments: here is why we keep pfn instead of page. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Petr Holasek <pholasek@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 1 changed file with 22 additions and 16 deletions Side-by-side Diff
mm/ksm.c
| ... | ... | @@ -1830,31 +1830,36 @@ |
| 1830 | 1830 | #endif /* CONFIG_MIGRATION */ |
| 1831 | 1831 | |
| 1832 | 1832 | #ifdef CONFIG_MEMORY_HOTREMOVE |
| 1833 | -static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, | |
| 1834 | - unsigned long end_pfn) | |
| 1833 | +static void ksm_check_stable_tree(unsigned long start_pfn, | |
| 1834 | + unsigned long end_pfn) | |
| 1835 | 1835 | { |
| 1836 | + struct stable_node *stable_node; | |
| 1836 | 1837 | struct rb_node *node; |
| 1837 | 1838 | int nid; |
| 1838 | 1839 | |
| 1839 | - for (nid = 0; nid < nr_node_ids; nid++) | |
| 1840 | - for (node = rb_first(&root_stable_tree[nid]); node; | |
| 1841 | - node = rb_next(node)) { | |
| 1842 | - struct stable_node *stable_node; | |
| 1843 | - | |
| 1840 | + for (nid = 0; nid < nr_node_ids; nid++) { | |
| 1841 | + node = rb_first(&root_stable_tree[nid]); | |
| 1842 | + while (node) { | |
| 1844 | 1843 | stable_node = rb_entry(node, struct stable_node, node); |
| 1845 | 1844 | if (stable_node->kpfn >= start_pfn && |
| 1846 | - stable_node->kpfn < end_pfn) | |
| 1847 | - return stable_node; | |
| 1845 | + stable_node->kpfn < end_pfn) { | |
| 1846 | + /* | |
| 1847 | + * Don't get_ksm_page, page has already gone: | |
| 1848 | + * which is why we keep kpfn instead of page* | |
| 1849 | + */ | |
| 1850 | + remove_node_from_stable_tree(stable_node); | |
| 1851 | + node = rb_first(&root_stable_tree[nid]); | |
| 1852 | + } else | |
| 1853 | + node = rb_next(node); | |
| 1854 | + cond_resched(); | |
| 1848 | 1855 | } |
| 1849 | - | |
| 1850 | - return NULL; | |
| 1856 | + } | |
| 1851 | 1857 | } |
| 1852 | 1858 | |
| 1853 | 1859 | static int ksm_memory_callback(struct notifier_block *self, |
| 1854 | 1860 | unsigned long action, void *arg) |
| 1855 | 1861 | { |
| 1856 | 1862 | struct memory_notify *mn = arg; |
| 1857 | - struct stable_node *stable_node; | |
| 1858 | 1863 | |
| 1859 | 1864 | switch (action) { |
| 1860 | 1865 | case MEM_GOING_OFFLINE: |
| 1861 | 1866 | |
| ... | ... | @@ -1874,11 +1879,12 @@ |
| 1874 | 1879 | /* |
| 1875 | 1880 | * Most of the work is done by page migration; but there might |
| 1876 | 1881 | * be a few stable_nodes left over, still pointing to struct |
| 1877 | - * pages which have been offlined: prune those from the tree. | |
| 1882 | + * pages which have been offlined: prune those from the tree, | |
| 1883 | + * otherwise get_ksm_page() might later try to access a | |
| 1884 | + * non-existent struct page. | |
| 1878 | 1885 | */ |
| 1879 | - while ((stable_node = ksm_check_stable_tree(mn->start_pfn, | |
| 1880 | - mn->start_pfn + mn->nr_pages)) != NULL) | |
| 1881 | - remove_node_from_stable_tree(stable_node); | |
| 1886 | + ksm_check_stable_tree(mn->start_pfn, | |
| 1887 | + mn->start_pfn + mn->nr_pages); | |
| 1882 | 1888 | /* fallthrough */ |
| 1883 | 1889 | |
| 1884 | 1890 | case MEM_CANCEL_OFFLINE: |