@@ -672,16 +672,25 @@ static int __migrate_folio(struct address_space *mapping, struct folio *dst,
struct folio *src, void *src_private,
enum migrate_mode mode)
{
- int rc;
+ int rc, expected_cnt = folio_expected_refs(mapping, src);
- rc = folio_migrate_mapping(mapping, dst, src, 0);
- if (rc != MIGRATEPAGE_SUCCESS)
+ rc = folio_refs_check_and_freeze(mapping, src, expected_cnt);
+ if (rc)
return rc;
+ rc = folio_mc_copy(dst, src);
+ if (rc) {
+ if (mapping)
+ folio_ref_unfreeze(src, expected_cnt);
+ return rc;
+ }
+
+ folio_replace_mapping_and_unfreeze(mapping, dst, src, expected_cnt);
+
if (src_private)
folio_attach_private(dst, folio_detach_private(src));
- folio_migrate_copy(dst, src);
+ folio_migrate_flags(dst, src);
return MIGRATEPAGE_SUCCESS;
}
The folio migration is widely used in kernel, memory compaction, memory hotplug, soft offline page, numa balance, memory demote/promotion, etc, but once access a poisoned source folio when migrating, the kerenl will panic. There is a mechanism in the kernel to recover from uncorrectable memory errors, ARCH_HAS_COPY_MC, which is already used in other core-mm paths, eg, CoW, khugepaged, coredump, ksm copy, see copy_mc_to_{user,kernel}, copy_mc_{user_}highpage callers. In order to support poisoned folio copy recover from migrate folio, we chose to make folio migration tolerant of memory failures and return error for folio migration, because folio migration is no guarantee of success, this could avoid the similar panic shown below. CPU: 1 PID: 88343 Comm: test_softofflin Kdump: loaded Not tainted 6.6.0 pc : copy_page+0x10/0xc0 lr : copy_highpage+0x38/0x50 ... Call trace: copy_page+0x10/0xc0 folio_copy+0x78/0x90 migrate_folio_extra+0x54/0xa0 move_to_new_folio+0xd8/0x1f0 migrate_folio_move+0xb8/0x300 migrate_pages_batch+0x528/0x788 migrate_pages_sync+0x8c/0x258 migrate_pages+0x440/0x528 soft_offline_in_use_page+0x2ec/0x3c0 soft_offline_page+0x238/0x310 soft_offline_page_store+0x6c/0xc0 dev_attr_store+0x20/0x40 sysfs_kf_write+0x4c/0x68 kernfs_fop_write_iter+0x130/0x1c8 new_sync_write+0xa4/0x138 vfs_write+0x238/0x2d8 ksys_write+0x74/0x110 Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> --- mm/migrate.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)