lkml.org 
[lkml]   [2021]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    SubjectRe: [PATCH v3 1/3] mm/hwpoison: mf_mutex for soft offline and unpoison
    On Thu, Nov 4, 2021 at 10:52 PM Naoya Horiguchi
    <naoya.horiguchi@linux.dev> wrote:
    >
    > From: Naoya Horiguchi <naoya.horiguchi@nec.com>
    >
    > Originally mf_mutex is introduced to serialize multiple MCE events, but
    > it is not that useful to allow unpoison to run in parallel with memory_failure()
    > and soft offline. So apply mf_they to soft offline and unpoison.
    ^^^^^^^^
    A typo? It should be mf_mutex, right?

    Looks good to me other than the above nit. Reviewed-by: Yang Shi
    <shy828301@gmail.com>

    > The memory failure handler and soft offline handler get simpler with this.
    >
    > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
    > ---
    > ChangeLog v3:
    > - merge with "mm/hwpoison: remove race consideration"
    > - update description
    >
    > ChangeLog v2:
    > - add mutex_unlock() in "page already poisoned" path in soft_offline_page().
    > (Thanks to Ding Hui)
    > ---
    > mm/memory-failure.c | 62 +++++++++++++--------------------------------
    > 1 file changed, 18 insertions(+), 44 deletions(-)
    >
    > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
    > index e8c38e27b753..d29c79de6034 100644
    > --- a/mm/memory-failure.c
    > +++ b/mm/memory-failure.c
    > @@ -1507,14 +1507,6 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
    > lock_page(head);
    > page_flags = head->flags;
    >
    > - if (!PageHWPoison(head)) {
    > - pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
    > - num_poisoned_pages_dec();
    > - unlock_page(head);
    > - put_page(head);
    > - return 0;
    > - }
    > -
    > /*
    > * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
    > * simply disable it. In order to make it work properly, we need
    > @@ -1628,6 +1620,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
    > return rc;
    > }
    >
    > +static DEFINE_MUTEX(mf_mutex);
    > +
    > /**
    > * memory_failure - Handle memory failure of a page.
    > * @pfn: Page Number of the corrupted page
    > @@ -1654,7 +1648,6 @@ int memory_failure(unsigned long pfn, int flags)
    > int res = 0;
    > unsigned long page_flags;
    > bool retry = true;
    > - static DEFINE_MUTEX(mf_mutex);
    >
    > if (!sysctl_memory_failure_recovery)
    > panic("Memory failure on page %lx", pfn);
    > @@ -1788,16 +1781,6 @@ int memory_failure(unsigned long pfn, int flags)
    > */
    > page_flags = p->flags;
    >
    > - /*
    > - * unpoison always clear PG_hwpoison inside page lock
    > - */
    > - if (!PageHWPoison(p)) {
    > - pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
    > - num_poisoned_pages_dec();
    > - unlock_page(p);
    > - put_page(p);
    > - goto unlock_mutex;
    > - }
    > if (hwpoison_filter(p)) {
    > if (TestClearPageHWPoison(p))
    > num_poisoned_pages_dec();
    > @@ -1978,6 +1961,7 @@ int unpoison_memory(unsigned long pfn)
    > struct page *page;
    > struct page *p;
    > int freeit = 0;
    > + int ret = 0;
    > unsigned long flags = 0;
    > static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
    > DEFAULT_RATELIMIT_BURST);
    > @@ -1988,39 +1972,30 @@ int unpoison_memory(unsigned long pfn)
    > p = pfn_to_page(pfn);
    > page = compound_head(p);
    >
    > + mutex_lock(&mf_mutex);
    > +
    > if (!PageHWPoison(p)) {
    > unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
    > pfn, &unpoison_rs);
    > - return 0;
    > + goto unlock_mutex;
    > }
    >
    > if (page_count(page) > 1) {
    > unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
    > pfn, &unpoison_rs);
    > - return 0;
    > + goto unlock_mutex;
    > }
    >
    > if (page_mapped(page)) {
    > unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
    > pfn, &unpoison_rs);
    > - return 0;
    > + goto unlock_mutex;
    > }
    >
    > if (page_mapping(page)) {
    > unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
    > pfn, &unpoison_rs);
    > - return 0;
    > - }
    > -
    > - /*
    > - * unpoison_memory() can encounter thp only when the thp is being
    > - * worked by memory_failure() and the page lock is not held yet.
    > - * In such case, we yield to memory_failure() and make unpoison fail.
    > - */
    > - if (!PageHuge(page) && PageTransHuge(page)) {
    > - unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
    > - pfn, &unpoison_rs);
    > - return 0;
    > + goto unlock_mutex;
    > }
    >
    > if (!get_hwpoison_page(p, flags)) {
    > @@ -2028,29 +2003,23 @@ int unpoison_memory(unsigned long pfn)
    > num_poisoned_pages_dec();
    > unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
    > pfn, &unpoison_rs);
    > - return 0;
    > + goto unlock_mutex;
    > }
    >
    > - lock_page(page);
    > - /*
    > - * This test is racy because PG_hwpoison is set outside of page lock.
    > - * That's acceptable because that won't trigger kernel panic. Instead,
    > - * the PG_hwpoison page will be caught and isolated on the entrance to
    > - * the free buddy page pool.
    > - */
    > if (TestClearPageHWPoison(page)) {
    > unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
    > pfn, &unpoison_rs);
    > num_poisoned_pages_dec();
    > freeit = 1;
    > }
    > - unlock_page(page);
    >
    > put_page(page);
    > if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
    > put_page(page);
    >
    > - return 0;
    > +unlock_mutex:
    > + mutex_unlock(&mf_mutex);
    > + return ret;
    > }
    > EXPORT_SYMBOL(unpoison_memory);
    >
    > @@ -2231,9 +2200,12 @@ int soft_offline_page(unsigned long pfn, int flags)
    > return -EIO;
    > }
    >
    > + mutex_lock(&mf_mutex);
    > +
    > if (PageHWPoison(page)) {
    > pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
    > put_ref_page(ref_page);
    > + mutex_unlock(&mf_mutex);
    > return 0;
    > }
    >
    > @@ -2251,5 +2223,7 @@ int soft_offline_page(unsigned long pfn, int flags)
    > }
    > }
    >
    > + mutex_unlock(&mf_mutex);
    > +
    > return ret;
    > }
    > --
    > 2.25.1
    >
    >

    \
     
     \ /
      Last update: 2021-11-05 19:24    [W:3.026 / U:1.364 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site