From patchwork Thu Mar 26 12:24:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 11459969 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6B10315AB for ; Thu, 26 Mar 2020 12:24:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40E152076A for ; Thu, 26 Mar 2020 12:24:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fozePfDz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728049AbgCZMYa (ORCPT ); Thu, 26 Mar 2020 08:24:30 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:35006 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727781AbgCZMYa (ORCPT ); Thu, 26 Mar 2020 08:24:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=rjxXUPkAV1fsLQ+udp/Q1rC9JBDjjV9DtFAl1poJf40=; b=fozePfDztlOQbzlhERCu3VnHRp IHZZQPqbVmbybpSq4Z9r3gpc6jcZATKHMO0uI1vpslmAb2eeck24ecqZO0WR3s1xbLa3OpgbkWl1+ hre2NDHKPqTTIuLHLS8Mjbhw0a0uzzkqMHQBVyUDgyjgiLbC8wUVH/RoLYCvfFAt0e/p7QTWY8qzz X3RvuW7UJpQFKxpWEEU98Fk7EKw0VOz0n6wbKd8QC/6BpHSylMqXZdeMlxWWftv3gSPvS3M6iJGuP +1hnMTD0zQm4uyUGGzMEUl0dUn0yiQWsWjeNkzjH2R6ECc48InnSeVQ+DYmyhXd1aX7ZHVxWldGsd QJmP5DWg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jHRYk-0005P4-7R; Thu, 26 Mar 2020 12:24:30 +0000 From: Matthew Wilcox To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" Subject: [PATCH 2/2] mm: Use clear_bit_unlock_is_negative_byte for PageWriteback Date: Thu, 26 Mar 2020 05:24:29 -0700 Message-Id: <20200326122429.20710-3-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200326122429.20710-1-willy@infradead.org> References: <20200326122429.20710-1-willy@infradead.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: "Matthew Wilcox (Oracle)" By moving PG_writeback down into the low bits of the page flags, we can use clear_bit_unlock_is_negative_byte() for writeback as well as the lock bit. wake_up_page() then has no more callers. Given the other code being executed between the clear and the test, this is not going to be as dramatic a win as it was for PageLocked, but symmetry between the two is nice and lets us remove some code. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Jan Kara Reviewed-by: William Kucharski --- include/linux/page-flags.h | 6 +++--- mm/filemap.c | 19 ++++++------------- mm/page-writeback.c | 37 ++++++++++++++++++++----------------- 3 files changed, 29 insertions(+), 33 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 222f6f7b2bb3..96c7d220c8cf 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -103,13 +103,14 @@ */ enum pageflags { PG_locked, /* Page is locked. Don't touch. */ + PG_writeback, /* Page is under writeback */ PG_referenced, PG_uptodate, PG_dirty, PG_lru, PG_active, + PG_waiters, /* Page has waiters, check its waitqueue */ PG_workingset, - PG_waiters, /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */ PG_error, PG_slab, PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/ @@ -117,7 +118,6 @@ enum pageflags { PG_reserved, PG_private, /* If pagecache, has fs-private data */ PG_private_2, /* If pagecache, has fs aux data */ - PG_writeback, /* Page is under writeback */ PG_head, /* A head page */ PG_mappedtodisk, /* Has blocks allocated on-disk */ PG_reclaim, /* To be reclaimed asap */ @@ -545,7 +545,7 @@ static __always_inline void SetPageUptodate(struct page *page) CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL) -int test_clear_page_writeback(struct page *page); +bool __clear_page_writeback(struct page *page); int __test_set_page_writeback(struct page *page, bool keep_write); #define test_set_page_writeback(page) \ diff --git a/mm/filemap.c b/mm/filemap.c index 312afbfcb49a..bfe1782a7b98 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1084,13 +1084,6 @@ static void wake_up_page_bit(struct page *page, int bit_nr) spin_unlock_irqrestore(&q->lock, flags); } -static void wake_up_page(struct page *page, int bit) -{ - if (!PageWaiters(page)) - return; - wake_up_page_bit(page, bit); -} - /* * A choice of three behaviors for wait_on_page_bit_common(): */ @@ -1266,6 +1259,7 @@ EXPORT_SYMBOL_GPL(add_page_wait_queue); void unlock_page(struct page *page) { BUILD_BUG_ON(PG_waiters != 7); + BUILD_BUG_ON(PG_locked > 7); page = compound_head(page); VM_BUG_ON_PAGE(!PageLocked(page), page); if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) @@ -1279,23 +1273,22 @@ EXPORT_SYMBOL(unlock_page); */ void end_page_writeback(struct page *page) { + BUILD_BUG_ON(PG_writeback > 7); /* * TestClearPageReclaim could be used here but it is an atomic * operation and overkill in this particular case. Failing to * shuffle a page marked for immediate reclaim is too mild to * justify taking an atomic operation penalty at the end of - * ever page writeback. + * every page writeback. */ if (PageReclaim(page)) { ClearPageReclaim(page); rotate_reclaimable_page(page); } - if (!test_clear_page_writeback(page)) - BUG(); - - smp_mb__after_atomic(); - wake_up_page(page, PG_writeback); + VM_BUG_ON_PAGE(!PageWriteback(page), page); + if (__clear_page_writeback(page)) + wake_up_page_bit(page, PG_writeback); } EXPORT_SYMBOL(end_page_writeback); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index b7f3d0766a5f..4d675a7b81e6 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -595,7 +595,7 @@ static void wb_domain_writeout_inc(struct wb_domain *dom, /* * Increment @wb's writeout completion count and the global writeout - * completion count. Called from test_clear_page_writeback(). + * completion count. Called from __clear_page_writeback(). */ static inline void __wb_writeout_inc(struct bdi_writeback *wb) { @@ -2711,12 +2711,19 @@ int clear_page_dirty_for_io(struct page *page) } EXPORT_SYMBOL(clear_page_dirty_for_io); -int test_clear_page_writeback(struct page *page) +#define clear_writeback_bit(page) \ + clear_bit_unlock_is_negative_byte(PG_writeback, &page->flags) + +/* + * The return value is whether there are waiters pending, not whether + * the flag was set. + */ +bool __clear_page_writeback(struct page *page) { struct address_space *mapping = page_mapping(page); struct mem_cgroup *memcg; struct lruvec *lruvec; - int ret; + bool ret; memcg = lock_page_memcg(page); lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page)); @@ -2726,16 +2733,14 @@ int test_clear_page_writeback(struct page *page) unsigned long flags; xa_lock_irqsave(&mapping->i_pages, flags); - ret = TestClearPageWriteback(page); - if (ret) { - __xa_clear_mark(&mapping->i_pages, page_index(page), + ret = clear_writeback_bit(page); + __xa_clear_mark(&mapping->i_pages, page_index(page), PAGECACHE_TAG_WRITEBACK); - if (bdi_cap_account_writeback(bdi)) { - struct bdi_writeback *wb = inode_to_wb(inode); + if (bdi_cap_account_writeback(bdi)) { + struct bdi_writeback *wb = inode_to_wb(inode); - dec_wb_stat(wb, WB_WRITEBACK); - __wb_writeout_inc(wb); - } + dec_wb_stat(wb, WB_WRITEBACK); + __wb_writeout_inc(wb); } if (mapping->host && !mapping_tagged(mapping, @@ -2744,7 +2749,7 @@ int test_clear_page_writeback(struct page *page) xa_unlock_irqrestore(&mapping->i_pages, flags); } else { - ret = TestClearPageWriteback(page); + ret = clear_writeback_bit(page); } /* * NOTE: Page might be free now! Writeback doesn't hold a page @@ -2752,11 +2757,9 @@ int test_clear_page_writeback(struct page *page) * the clearing of PG_writeback. The below can only access * page state that is static across allocation cycles. */ - if (ret) { - dec_lruvec_state(lruvec, NR_WRITEBACK); - dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); - inc_node_page_state(page, NR_WRITTEN); - } + dec_lruvec_state(lruvec, NR_WRITEBACK); + dec_zone_page_state(page, NR_ZONE_WRITE_PENDING); + inc_node_page_state(page, NR_WRITTEN); __unlock_page_memcg(memcg); return ret; }