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    SubjectRe: [RFC PATCH 4/5] mm, memory_hotplug: print reason for the offlining failure
    On Wed,  7 Nov 2018 11:18:29 +0100 Michal Hocko <mhocko@kernel.org> wrote:

    > From: Michal Hocko <mhocko@suse.com>
    >
    > The memory offlining failure reporting is inconsistent and insufficient.
    > Some error paths simply do not report the failure to the log at all.
    > When we do report there are no details about the reason of the failure
    > and there are several of them which makes memory offlining failures
    > hard to debug.
    >
    > Make sure that the
    > memory offlining [mem %#010llx-%#010llx] failed
    > message is printed for all failures and also provide a short textual
    > reason for the failure e.g.
    >
    > [ 1984.506184] rac1 kernel: memory offlining [mem 0x82600000000-0x8267fffffff] failed due to signal backoff
    >
    > this tells us that the offlining has failed because of a signal pending
    > aka user intervention.
    >
    > ...

    Some of these messages will come out looking a bit odd.

    > @@ -1573,7 +1576,8 @@ static int __ref __offline_pages(unsigned long start_pfn,
    > MIGRATE_MOVABLE, true);
    > if (ret) {
    > mem_hotplug_done();
    > - return ret;
    > + reason = "failed to isolate range";

    "memory offlining [mem ...] failed due to failed to isolate range"

    > + goto failed_removal
    > }
    >
    > arg.start_pfn = start_pfn;
    > @@ -1582,15 +1586,19 @@ static int __ref __offline_pages(unsigned long start_pfn,
    >
    > ret = memory_notify(MEM_GOING_OFFLINE, &arg);
    > ret = notifier_to_errno(ret);
    > - if (ret)
    > - goto failed_removal;
    > + if (ret) {
    > + reason = "notifiers failure";

    "memory offlining [mem ...] failed due to notifiers failure"

    > @@ -1607,8 +1615,10 @@ static int __ref __offline_pages(unsigned long start_pfn,
    > * actually in order to make hugetlbfs's object counting consistent.
    > */
    > ret = dissolve_free_huge_pages(start_pfn, end_pfn);
    > - if (ret)
    > - goto failed_removal;
    > + if (ret) {
    > + reason = "fails to disolve hugetlb pages";

    "memory offlining [mem ...] failed due to fails to disolve hugetlb pages"


    Fix:

    --- a/mm/memory_hotplug.c~mm-memory_hotplug-print-reason-for-the-offlining-failure-fix
    +++ a/mm/memory_hotplug.c
    @@ -1576,7 +1576,7 @@ static int __ref __offline_pages(unsigne
    MIGRATE_MOVABLE, true);
    if (ret) {
    mem_hotplug_done();
    - reason = "failed to isolate range";
    + reason = "failure to isolate range";
    goto failed_removal
    }

    @@ -1587,7 +1587,7 @@ static int __ref __offline_pages(unsigne
    ret = memory_notify(MEM_GOING_OFFLINE, &arg);
    ret = notifier_to_errno(ret);
    if (ret) {
    - reason = "notifiers failure";
    + reason = "notifier failure";
    goto failed_removal_isolated;
    }

    @@ -1616,7 +1616,7 @@ repeat:
    */
    ret = dissolve_free_huge_pages(start_pfn, end_pfn);
    if (ret) {
    - reason = "fails to disolve hugetlb pages";
    + reason = "failure to dissolve huge pages";
    goto failed_removal_isolated;
    }
    /* check again */
    _
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      Last update: 2018-11-07 23:05    [W:6.558 / U:0.032 seconds]
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