From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 718071FB7 for ; Fri, 25 Mar 2022 01:09:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E8DDC340ED; Fri, 25 Mar 2022 01:09:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648170590; bh=EEBzXX9FqejaMH4HLz4mbN6zJ46CBwBkgiWCFAKq4r4=; h=Date:To:From:In-Reply-To:Subject:From; b=Mjz8eu+amio4lsxBq2Ni0P1xfkdb0jjua+i8/eEHmJ6GoiVmHS5gD01Vmku2NsH22 OEAsl30nPWYGuB0xJJKwjWGEiMMxxTyWH3PRyIp2F54aoVUXvevBf5XPPKwlM1j40D EalQJWs/tkoLYEolU7ufRfszNgW416DUYWSntnjs= Date: Thu, 24 Mar 2022 18:09:49 -0700 To: yuzhao@google.com,willy@infradead.org,shy828301@gmail.com,npiggin@gmail.com,mhocko@suse.com,david@redhat.com,hughd@google.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220324180758.96b1ac7e17675d6bc474485e@linux-foundation.org> Subject: [patch 025/114] mm: delete __ClearPageWaiters() Message-Id: <20220325010950.3E8DDC340ED@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: Hugh Dickins Subject: mm: delete __ClearPageWaiters() The PG_waiters bit is not included in PAGE_FLAGS_CHECK_AT_FREE, and vmscan.c's free_unref_page_list() callers rely on that not to generate bad_page() alerts. So __page_cache_release(), put_pages_list() and release_pages() (and presumably copy-and-pasted free_zone_device_page()) are redundant and misleading to make a special point of clearing it (as the "__" implies, it could only safely be used on the freeing path). Delete __ClearPageWaiters(). Remark on this in one of the "possible" comments in folio_wake_bit(), and delete the superfluous comments. Link: https://lkml.kernel.org/r/3eafa969-5b1a-accf-88fe-318784c791a@google.com Signed-off-by: Hugh Dickins Tested-by: Yu Zhao Reviewed-by: Yang Shi Reviewed-by: David Hildenbrand Cc: Matthew Wilcox Cc: Nicholas Piggin Cc: Yu Zhao Cc: Michal Hocko Signed-off-by: Andrew Morton --- include/linux/page-flags.h | 2 +- mm/filemap.c | 23 ++++++++--------------- mm/memremap.c | 2 -- mm/swap.c | 4 ---- 4 files changed, 9 insertions(+), 22 deletions(-) --- a/include/linux/page-flags.h~mm-delete-__clearpagewaiters +++ a/include/linux/page-flags.h @@ -481,7 +481,7 @@ static inline int TestClearPage##uname(s TESTSETFLAG_FALSE(uname, lname) TESTCLEARFLAG_FALSE(uname, lname) __PAGEFLAG(Locked, locked, PF_NO_TAIL) -PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) +PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL) PAGEFLAG(Referenced, referenced, PF_HEAD) TESTCLEARFLAG(Referenced, referenced, PF_HEAD) --- a/mm/filemap.c~mm-delete-__clearpagewaiters +++ a/mm/filemap.c @@ -1185,24 +1185,17 @@ static void folio_wake_bit(struct folio } /* - * It is possible for other pages to have collided on the waitqueue - * hash, so in that case check for a page match. That prevents a long- - * term waiter + * It's possible to miss clearing waiters here, when we woke our page + * waiters, but the hashed waitqueue has waiters for other pages on it. + * That's okay, it's a rare case. The next waker will clear it. * - * It is still possible to miss a case here, when we woke page waiters - * and removed them from the waitqueue, but there are still other - * page waiters. + * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE, + * other), the flag may be cleared in the course of freeing the page; + * but that is not required for correctness. */ - if (!waitqueue_active(q) || !key.page_match) { + if (!waitqueue_active(q) || !key.page_match) folio_clear_waiters(folio); - /* - * It's possible to miss clearing Waiters here, when we woke - * our page waiters, but the hashed waitqueue has waiters for - * other pages on it. - * - * That's okay, it's a rare case. The next waker will clear it. - */ - } + spin_unlock_irqrestore(&q->lock, flags); } --- a/mm/memremap.c~mm-delete-__clearpagewaiters +++ a/mm/memremap.c @@ -456,8 +456,6 @@ void free_zone_device_page(struct page * if (WARN_ON_ONCE(!page->pgmap->ops || !page->pgmap->ops->page_free)) return; - __ClearPageWaiters(page); - mem_cgroup_uncharge(page_folio(page)); /* --- a/mm/swap.c~mm-delete-__clearpagewaiters +++ a/mm/swap.c @@ -97,7 +97,6 @@ static void __page_cache_release(struct mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages); } - __ClearPageWaiters(page); } static void __put_single_page(struct page *page) @@ -152,7 +151,6 @@ void put_pages_list(struct list_head *pa continue; } /* Cannot be PageLRU because it's passed to us using the lru */ - __ClearPageWaiters(page); } free_unref_page_list(pages); @@ -971,8 +969,6 @@ void release_pages(struct page **pages, count_vm_event(UNEVICTABLE_PGCLEARED); } - __ClearPageWaiters(page); - list_add(&page->lru, &pages_to_free); } if (lruvec) _