Messages in this thread Patch in this message | | | From | Huang Ying <> | Subject | [PATCH -V3 1/8] migrate: fix syscall move_pages() return value for failure | Date | Wed, 17 Aug 2022 16:14:01 +0800 |
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The return value of move_pages() syscall is incorrect when counting the remaining pages to be migrated. For example, for the following test program,
" #define _GNU_SOURCE
#include <stdbool.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <errno.h>
#include <fcntl.h> #include <sys/uio.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> #include <numaif.h> #include <numa.h>
#ifndef MADV_FREE #define MADV_FREE 8 /* free pages only if memory pressure */ #endif
#define ONE_MB (1024 * 1024) #define MAP_SIZE (16 * ONE_MB) #define THP_SIZE (2 * ONE_MB) #define THP_MASK (THP_SIZE - 1)
#define ERR_EXIT_ON(cond, msg) \ do { \ int __cond_in_macro = (cond); \ if (__cond_in_macro) \ error_exit(__cond_in_macro, (msg)); \ } while (0)
void error_msg(int ret, int nr, int *status, const char *msg) { int i;
fprintf(stderr, "Error: %s, ret : %d, error: %s\n", msg, ret, strerror(errno));
if (!nr) return; fprintf(stderr, "status: "); for (i = 0; i < nr; i++) fprintf(stderr, "%d ", status[i]); fprintf(stderr, "\n"); }
void error_exit(int ret, const char *msg) { error_msg(ret, 0, NULL, msg); exit(1); }
int page_size;
bool do_vmsplice; bool do_thp;
static int pipe_fds[2]; void *addr; char *pn; char *pn1; void *pages[2]; int status[2];
void prepare() { int ret; struct iovec iov;
if (addr) { munmap(addr, MAP_SIZE); close(pipe_fds[0]); close(pipe_fds[1]); }
ret = pipe(pipe_fds); ERR_EXIT_ON(ret, "pipe");
addr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); ERR_EXIT_ON(addr == MAP_FAILED, "mmap"); if (do_thp) { ret = madvise(addr, MAP_SIZE, MADV_HUGEPAGE); ERR_EXIT_ON(ret, "advise hugepage"); }
pn = (char *)(((unsigned long)addr + THP_SIZE) & ~THP_MASK); pn1 = pn + THP_SIZE; pages[0] = pn; pages[1] = pn1; *pn = 1;
if (do_vmsplice) { iov.iov_base = pn; iov.iov_len = page_size; ret = vmsplice(pipe_fds[1], &iov, 1, 0); ERR_EXIT_ON(ret < 0, "vmsplice"); }
status[0] = status[1] = 1024; }
void test_migrate() { int ret; int nodes[2] = { 1, 1 }; pid_t pid = getpid();
prepare(); ret = move_pages(pid, 1, pages, nodes, status, MPOL_MF_MOVE_ALL); error_msg(ret, 1, status, "move 1 page");
prepare(); ret = move_pages(pid, 2, pages, nodes, status, MPOL_MF_MOVE_ALL); error_msg(ret, 2, status, "move 2 pages, page 1 not mapped");
prepare(); *pn1 = 1; ret = move_pages(pid, 2, pages, nodes, status, MPOL_MF_MOVE_ALL); error_msg(ret, 2, status, "move 2 pages");
prepare(); *pn1 = 1; nodes[1] = 0; ret = move_pages(pid, 2, pages, nodes, status, MPOL_MF_MOVE_ALL); error_msg(ret, 2, status, "move 2 pages, page 1 to node 0"); }
int main(int argc, char *argv[]) { numa_run_on_node(0); page_size = getpagesize();
test_migrate();
fprintf(stderr, "\nMake page 0 cannot be migrated:\n"); do_vmsplice = true; test_migrate();
fprintf(stderr, "\nTest THP:\n"); do_thp = true; do_vmsplice = false; test_migrate();
fprintf(stderr, "\nTHP: make page 0 cannot be migrated:\n"); do_vmsplice = true; test_migrate();
return 0; } "
The output of the current kernel is,
" Error: move 1 page, ret : 0, error: Success status: 1 Error: move 2 pages, page 1 not mapped, ret : 0, error: Success status: 1 -14 Error: move 2 pages, ret : 0, error: Success status: 1 1 Error: move 2 pages, page 1 to node 0, ret : 0, error: Success status: 1 0
Make page 0 cannot be migrated: Error: move 1 page, ret : 0, error: Success status: 1024 Error: move 2 pages, page 1 not mapped, ret : 1, error: Success status: 1024 -14 Error: move 2 pages, ret : 0, error: Success status: 1024 1024 Error: move 2 pages, page 1 to node 0, ret : 1, error: Success status: 1024 1024 "
While the expected output is,
" Error: move 1 page, ret : 0, error: Success status: 1 Error: move 2 pages, page 1 not mapped, ret : 0, error: Success status: 1 -14 Error: move 2 pages, ret : 0, error: Success status: 1 1 Error: move 2 pages, page 1 to node 0, ret : 0, error: Success status: 1 0
Make page 0 cannot be migrated: Error: move 1 page, ret : 1, error: Success status: 1024 Error: move 2 pages, page 1 not mapped, ret : 1, error: Success status: 1024 -14 Error: move 2 pages, ret : 1, error: Success status: 1024 1024 Error: move 2 pages, page 1 to node 0, ret : 2, error: Success status: 1024 1024 "
Fix this via correcting the remaining pages counting. With the fix, the output for the test program as above is expected.
Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages") Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Yang Shi <shy828301@gmail.com> --- mm/migrate.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c index a35eba462e61..1758fd215c0a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1751,7 +1751,7 @@ static int move_pages_and_store_status(struct mm_struct *mm, int node, * well. */ if (err > 0) - err += nr_pages - i - 1; + err += nr_pages - i; return err; } return store_status(status, start, node, i - start); @@ -1837,8 +1837,12 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, err = move_pages_and_store_status(mm, current_node, &pagelist, status, start, i, nr_pages); - if (err) + if (err) { + /* We have accounted for page i */ + if (err > 0) + err--; goto out; + } current_node = NUMA_NO_NODE; } out_flush: -- 2.30.2
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