The patch titled
Subject: mm,hwpoison: refactor get_any_page
has been added to the -mm tree. Its filename is
mmhwpoison-refactor-get_any_page.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mmhwpoison-refactor-get_any_page.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mmhwpoison-refactor-get_any_page.patch
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------------------------------------------------------
From: Oscar Salvador <osalvador@xxxxxxx>
Subject: mm,hwpoison: refactor get_any_page
Patch series "HWPoison: Refactor get page interface"
This patchset does three things:
1) Drops MF_COUNT_INCREASED trick
2) Refactors get page interface
3) Places a common entry for grabbin a page from both hard offline
and soft offline guarded by zone_pcp_{disable/enable}, so we do not
have to drain pcplists by ourself and retry again.
Note that the MF_COUNT_INCREASED trick was left because if get_hwpoison_page
races with put_page (e.g:)
CPU0 CPU1
put_page (refcount decremented to 0)
__put_single_page
free_unref_page
free_unref_page_prepare
free_pcp_prepare
free_pages_prepare soft_offline_page
:page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP get_any_page
get_hwpoison_page
free_unref_page_commit
free_one_page
__free_one_page (place it in buddy)
get_hwpoison_page sees that page has a refcount of 0, but since it was not
placed in buddy yet we cannot really handle it. We now have a sort of
maximum passes in get_any_page, so in case we race with either an
allocation or a put_page, we retry again.
After an off-list discussion with Naoya, he agreed to proceed.
[1] https://patchwork.kernel.org/project/linux-mm/list/?series=364009
[2] https://patchwork.kernel.org/project/linux-mm/list/?series=381903
This patch (of 7):
When we want to grab a refcount via get_any_page, we call __get_any_page
that calls get_hwpoison_page to get the actual refcount.
get_any_page is only there because we have a sort of retry mechanism in
case the page we met is unknown to us or if we raced with an allocation.
Also __get_any_page prints some messages about the page type in case the
page was a free page or the page type was unknown, but if anything, we
only need to print a message in case the pagetype was unknown, as that is
reporting an error down the chain.
Let us merge get_any_page and __get_any_page, and let the message be
printed in soft_offline_page.
Link: https://lkml.kernel.org/r/20201119105716.5962-1-osalvador@xxxxxxx
Link: https://lkml.kernel.org/r/20201119105716.5962-2-osalvador@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 91 +++++++++++++++++-------------------------
1 file changed, 37 insertions(+), 54 deletions(-)
--- a/mm/memory-failure.c~mmhwpoison-refactor-get_any_page
+++ a/mm/memory-failure.c
@@ -1707,70 +1707,49 @@ EXPORT_SYMBOL(unpoison_memory);
/*
* Safely get reference count of an arbitrary page.
- * Returns 0 for a free page, -EIO for a zero refcount page
- * that is not free, and 1 for any other page type.
- * For 1 the page is returned with increased page count, otherwise not.
+ * Returns 0 for a free page, 1 for an in-use page, -EIO for a page-type we
+ * cannot handle and -EBUSY if we raced with an allocation.
+ * We only incremented refcount in case the page was already in-use and it is
+ * a known type we can handle.
*/
-static int __get_any_page(struct page *p, unsigned long pfn, int flags)
+static int get_any_page(struct page *p, unsigned long pfn, int flags)
{
- int ret;
+ int ret = 0, pass = 0;
if (flags & MF_COUNT_INCREASED)
return 1;
- /*
- * When the target page is a free hugepage, just remove it
- * from free hugepage list.
- */
+try_again:
if (!get_hwpoison_page(p)) {
- if (PageHuge(p)) {
- pr_info("%s: %#lx free huge page\n", __func__, pfn);
- ret = 0;
- } else if (is_free_buddy_page(p)) {
- pr_info("%s: %#lx free buddy page\n", __func__, pfn);
- ret = 0;
- } else if (page_count(p)) {
- /* raced with allocation */
+ if (page_count(p)) {
+ /* We raced with an allocation, retry. */
+ if (pass++ < 3)
+ goto try_again;
ret = -EBUSY;
- } else {
- pr_info("%s: %#lx: unknown zero refcount page type %lx\n",
- __func__, pfn, p->flags);
+ } else if (!PageHuge(p) && !is_free_buddy_page(p)) {
+ /* We raced with put_page, retry. */
+ if (pass++ < 3)
+ goto try_again;
ret = -EIO;
}
} else {
- /* Not a free page */
- ret = 1;
- }
- return ret;
-}
-
-static int get_any_page(struct page *page, unsigned long pfn, int flags)
-{
- int ret = __get_any_page(page, pfn, flags);
-
- if (ret == -EBUSY)
- ret = __get_any_page(page, pfn, flags);
-
- if (ret == 1 && !PageHuge(page) &&
- !PageLRU(page) && !__PageMovable(page)) {
- /*
- * Try to free it.
- */
- put_page(page);
- shake_page(page, 1);
-
- /*
- * Did it turn free?
- */
- ret = __get_any_page(page, pfn, 0);
- if (ret == 1 && !PageLRU(page)) {
- /* Drop page reference which is from __get_any_page() */
- put_page(page);
- pr_info("soft_offline: %#lx: unknown non LRU page type %lx (%pGp)\n",
- pfn, page->flags, &page->flags);
- return -EIO;
+ if (PageHuge(p) || PageLRU(p) || __PageMovable(p)) {
+ ret = 1;
+ } else {
+ /*
+ * A page we cannot handle. Check whether we can turn
+ * it into something we can handle.
+ */
+ if (pass++ < 3) {
+ put_page(p);
+ shake_page(p, 1);
+ goto try_again;
+ }
+ put_page(p);
+ ret = -EIO;
}
}
+
return ret;
}
@@ -1939,7 +1918,7 @@ int soft_offline_page(unsigned long pfn,
return -EIO;
if (PageHWPoison(page)) {
- pr_info("soft offline: %#lx page already poisoned\n", pfn);
+ pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
if (flags & MF_COUNT_INCREASED)
put_page(page);
return 0;
@@ -1950,13 +1929,17 @@ retry:
ret = get_any_page(page, pfn, flags);
put_online_mems();
- if (ret > 0)
+ if (ret > 0) {
ret = soft_offline_in_use_page(page);
- else if (ret == 0)
+ } else if (ret == 0) {
if (soft_offline_free_page(page) && try_again) {
try_again = false;
goto retry;
}
+ } else if (ret == -EIO) {
+ pr_info("%s: %#lx: unknown page type: %lx (%pGP)\n",
+ __func__, pfn, page->flags, &page->flags);
+ }
return ret;
}
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
mmhwpoison-drain-pcplists-before-bailing-out-for-non-buddy-zero-refcount-page.patch
mmhwpoison-take-free-pages-off-the-buddy-freelists.patch
mmhwpoison-take-free-pages-off-the-buddy-freelists-for-hugetlb.patch
mmhwpoison-drop-unneeded-pcplist-draining.patch
mmhwpoison-refactor-get_any_page.patch
mmhwpoison-drop-pfn-parameter.patch
mmhwpoison-disable-pcplists-before-grabbing-a-refcount.patch
mmhwpoison-remove-drain_all_pages-from-shake_page.patch
mmhugetlb-remove-unneded-initialization.patch
