From e0153fc2c7606f101392b682e720a7a456d6c766 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Sat, 4 Jan 2020 12:59:46 -0800 Subject: [PATCH] mm: move_pages: return valid node id in status if the page is already on the target node Felix Abecassis reports move_pages() would return random status if the pages are already on the target node by the below test program: int main(void) { const long node_id = 1; const long page_size = sysconf(_SC_PAGESIZE); const int64_t num_pages = 8; unsigned long nodemask = 1 << node_id; long ret = set_mempolicy(MPOL_BIND, &nodemask, sizeof(nodemask)); if (ret < 0) return (EXIT_FAILURE); void **pages = malloc(sizeof(void*) * num_pages); for (int i = 0; i < num_pages; ++i) { pages[i] = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_POPULATE | MAP_ANONYMOUS, -1, 0); if (pages[i] == MAP_FAILED) return (EXIT_FAILURE); } ret = set_mempolicy(MPOL_DEFAULT, NULL, 0); if (ret < 0) return (EXIT_FAILURE); int *nodes = malloc(sizeof(int) * num_pages); int *status = malloc(sizeof(int) * num_pages); for (int i = 0; i < num_pages; ++i) { nodes[i] = node_id; status[i] = 0xd0; /* simulate garbage values */ } ret = move_pages(0, num_pages, pages, nodes, status, MPOL_MF_MOVE); printf("move_pages: %ld\n", ret); for (int i = 0; i < num_pages; ++i) printf("status[%d] = %d\n", i, status[i]); } Then running the program would return nonsense status values: $ ./move_pages_bug move_pages: 0 status[0] = 208 status[1] = 208 status[2] = 208 status[3] = 208 status[4] = 208 status[5] = 208 status[6] = 208 status[7] = 208 This is because the status is not set if the page is already on the target node, but move_pages() should return valid status as long as it succeeds. The valid status may be errno or node id. We can't simply initialize status array to zero since the pages may be not on node 0. Fix it by updating status with node id which the page is already on. Link: http://lkml.kernel.org/r/1575584353-125392-1-git-send-email-yang.shi@linux.alibaba.com Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") Signed-off-by: Yang Shi Reported-by: Felix Abecassis Tested-by: Felix Abecassis Suggested-by: Michal Hocko Reviewed-by: John Hubbard Acked-by: Christoph Lameter Acked-by: Michal Hocko Reviewed-by: Vlastimil Babka Cc: Mel Gorman Cc: [4.17+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/migrate.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index eae1565..86873b6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1512,9 +1512,11 @@ static int do_move_pages_to_node(struct mm_struct *mm, /* * Resolves the given address to a struct page, isolates it from the LRU and * puts it to the given pagelist. - * Returns -errno if the page cannot be found/isolated or 0 when it has been - * queued or the page doesn't need to be migrated because it is already on - * the target node + * Returns: + * errno - if the page cannot be found/isolated + * 0 - when it doesn't have to be migrated because it is already on the + * target node + * 1 - when it has been queued */ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, int node, struct list_head *pagelist, bool migrate_all) @@ -1553,7 +1555,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, if (PageHuge(page)) { if (PageHead(page)) { isolate_huge_page(page, pagelist); - err = 0; + err = 1; } } else { struct page *head; @@ -1563,7 +1565,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, if (err) goto out_putpage; - err = 0; + err = 1; list_add_tail(&head->lru, pagelist); mod_node_page_state(page_pgdat(head), NR_ISOLATED_ANON + page_is_file_cache(head), @@ -1640,8 +1642,17 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, */ err = add_page_for_migration(mm, addr, current_node, &pagelist, flags & MPOL_MF_MOVE_ALL); - if (!err) + + if (!err) { + /* The page is already on the target node */ + err = store_status(status, i, current_node, 1); + if (err) + goto out_flush; continue; + } else if (err > 0) { + /* The page is successfully queued for migration */ + continue; + } err = store_status(status, i, err, 1); if (err) -- 2.7.4