From: Oscar Salvador <osalvador@xxxxxxx> Subject: mm,hwpoison: refactor get_any_page Patch series "HWPoison: Refactor get page interface", v2. This patch (of 3): 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. Link: https://lkml.kernel.org/r/20201204102558.31607-1-osalvador@xxxxxxx Link: https://lkml.kernel.org/r/20201204102558.31607-2-osalvador@xxxxxxx Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Acked-by: Vlastimil Babka <Vbabka@xxxxxxx> Cc: Qian Cai <qcai@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory-failure.c | 99 +++++++++++++++++------------------------- 1 file changed, 42 insertions(+), 57 deletions(-) --- a/mm/memory-failure.c~mmhwpoison-refactor-get_any_page +++ a/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, 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, 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; } _
