[Devel] [PATCH RHEL7 COMMIT] ms/mm/mempolicy: Add cond_resched() in queue_pages_pte_range()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.11.1.vz7.39.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.1.vz7.39.7
------>
commit 4f22eedccf05e00ed355ed57f180de5fb3b46462
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date:   Tue Dec 19 13:38:42 2017 +0300

    ms/mm/mempolicy: Add cond_resched() in queue_pages_pte_range()
    
    Migrating huge range of memory may take quite some time, and
    with lack of resched point it may cause softlockup.
    
    NMI watchdog: BUG: soft lockup - CPU#57 stuck for 22s! [vcmmd:1942]
    RIP: 0010:[<ffffffff811a7c06>]  [<ffffffff811a7c06>] isolate_lru_page+0x86/0x1c0
    ...
    Call Trace:
     queue_pages_range+0x481/0x6d0
     migrate_to_node+0x79/0xe0
     do_migrate_pages+0x268/0x2d0
     cpuset_migrate_mm+0xcc/0xf0
     cpuset_change_nodemask+0x8e/0x90
     cgroup_scan_tasks+0x147/0x200
     update_tasks_nodemask+0x4b/0x70
     cpuset_migrate_mm+0xf0/0xf0
     cpuset_write_resmask+0x6b4/0x6f0
     lru_cache_add_active_or_unevictable+0x27/0xb0
     cgroup_rightmost_descendant+0x80/0x80
     cpuset_css_offline+0x50/0x50
     cgroup_file_write+0x1fe/0x2f0
     sb_start_write+0x58/0x110
     vfs_write+0xbd/0x1e0
     SyS_write+0x7f/0xe0
     system_call_fastpath+0x16/0x1b
    
    Add cond_resched() to fix that.
    
    Upstream got similar cond_resched() in commit
    6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()")
    
    https://jira.sw.ru/browse/PSBM-79273
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 mm/mempolicy.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9b0dcf1835c4..7bf644c82837 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -513,6 +513,7 @@ static int queue_pages_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 			break;
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 	pte_unmap_unlock(orig_pte, ptl);
+	cond_resched();
 	return addr != end;
 }