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Message-Id: <20201204102558.31607-2-osalvador@suse.de>
Date: Fri, 4 Dec 2020 11:25:56 +0100
From: Oscar Salvador <osalvador@...e.de>
To: akpm@...ux-foundation.org
Cc: n-horiguchi@...jp.nec.com, vbabka@...e.cz, qcai@...hat.com,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 1/3] mm,hwpoison: Refactor get_any_page
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.
While we are it, we can also remove the 'pfn' parameter as it is no
longer used.
Signed-off-by: Oscar Salvador <osalvador@...e.de>
Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
Acked-by: Vlastimil Babka <Vbabka@...e.cz>
---
mm/memory-failure.c | 99 +++++++++++++++++++--------------------------
1 file changed, 42 insertions(+), 57 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 869ece2a1de2..fb4068d52b87 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1707,70 +1707,51 @@ 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, int flags)
{
- int ret;
+ int ret = 0, pass = 0;
+ bool count_increased = false;
if (flags & MF_COUNT_INCREASED)
- return 1;
+ count_increased = true;
- /*
- * When the target page is a free hugepage, just remove it
- * from free hugepage list.
- */
- 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 */
+try_again:
+ if (!count_increased && !get_hwpoison_page(p)) {
+ 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);
+ count_increased = false;
+ goto try_again;
+ }
+ put_page(p);
+ ret = -EIO;
}
}
+
return ret;
}
@@ -1939,7 +1920,7 @@ int soft_offline_page(unsigned long pfn, int flags)
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;
@@ -1947,16 +1928,20 @@ int soft_offline_page(unsigned long pfn, int flags)
retry:
get_online_mems();
- ret = get_any_page(page, pfn, flags);
+ ret = get_any_page(page, 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;
}
--
2.26.2
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