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 321F03659FB; Fri, 1 May 2026 09:50:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777629020; cv=none; b=ndU3P2BCwvKH1Xg2+Pnr0JG9EIvK7WrurNtLNdT0pC4jZgGq1Uql7omknCC82Dkw2xPrrrFfGIfkH2gyofORnOZB2+Jh2VLpl+zEluoMwvIxtiH41+VyAeac+JCi87TLy8HhkF+yTkVT2amXMi7qPkZwpie/6cwUTnvWEyGC32M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777629020; c=relaxed/simple; bh=4CYXeOlFdNJ/l03z2utNHrOYCz+YwEmVX7CEA57VKaQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=VN8S7tuKcjb91wcocshIxSZ6YNPnJIw5A+MQ8tWLze5itQWY/O5pgGr6CURJKOQQV2PiWKPElelhvcUv3izu/Ei0s7gwdroKmSmbfqfbg+wBqyLCdeiFzzTsUgSy6DPxcpYCTxsVRDQ4KMh357HGQqugwMTWW02aLRm8t+hjHNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kKVnoSQr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kKVnoSQr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D515DC2BCB7; Fri, 1 May 2026 09:50:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777629019; bh=4CYXeOlFdNJ/l03z2utNHrOYCz+YwEmVX7CEA57VKaQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=kKVnoSQrWJeDILj7+mIfDLX2WD/0fJg2ViILcSv46jpdeO9Vx4w9kZ3AW5tXAdSOT VqjrDTlg+ZM8yUOrQeTKFdDtbqtAJbkuE25QQv9n4mh+DLkOSnWP9ltsCfvQ0iKTrO aPUX4tQALCljkv8adxFtd6xicjVU+UKZSKcCcE0D9gnA67ltC8miBdOYnuiLS+UiGz 6qSbqes/CKa+6PETChdfQtDAvz+VZELHp/F9gTEozl9Cm7a5HqbsZYKT+QD6ecbhug 9IhKebdVDSvcBDKqPWOAAbQcqA+7duHlwUNjdhWLAWges5mS9/vKTAjVypZTmtO6u1 vYYq+7Mcfoc6g== From: Jeff Layton Date: Fri, 01 May 2026 10:49:35 +0100 Subject: [PATCH v4 1/4] mm: track DONTCACHE dirty pages per bdi_writeback Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260501-dontcache-v4-1-5d5e6dc71cb3@kernel.org> References: <20260501-dontcache-v4-0-5d5e6dc71cb3@kernel.org> In-Reply-To: <20260501-dontcache-v4-0-5d5e6dc71cb3@kernel.org> To: Alexander Viro , Christian Brauner , Jan Kara , "Matthew Wilcox (Oracle)" , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Mike Snitzer , Jens Axboe , Ritesh Harjani , Chuck Lever Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, Jeff Layton X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3683; i=jlayton@kernel.org; h=from:subject:message-id; bh=4CYXeOlFdNJ/l03z2utNHrOYCz+YwEmVX7CEA57VKaQ=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBp9HdPPFn55EVKdK2kssKhcP5f4apt0ClJopsC7 t1wRkqHf96JAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCafR3TwAKCRAADmhBGVaC FeqCD/0Zqep3sm7p/GXonKUD3Hrr+qlUGhzPqP4bv5R18zbFwInLPz9G7ypQwV1i3w8OE/BfKcb zYYwJQi7Oke6qUeEkVur0wj0z0ZP+G5rUK/HlhNVYzG+XQgomTnznPcMEBtbtwS7VYL+0anFLQf IG4wpFtM959wNowJe0wgV79AwhezsYimbD2BZzSiqk9vSibo+7jkRChHIpQCK9flDS10GJoSFO6 hPRiLSO4y8Gc6HE77vD+Cu6JinCmzhQ1Amy9Z7b94vzcyi4wjgDdYKlHtUMI/9zQP5Z5lWV9QXX Kk5sfuv1g8KQ885ZXKDkq91bWtTZCJdHzPDPu0L5KI3w7jIWZh+39y+C/XIYHlxJ9AMFcVYwpo+ 4BFipwwcEpXuO064LT9CkbFddWSfPR83RDoV2H4N5Inylh8sqVp7LdnRT2H9TmDbEDWAaEdJoff G5HgvlhpoPevt7C9nFP9h8Kz4Gnz4hsF0xaeyMLzJIF01liLM5VNPr32utprTE75JCxrX5Vag4e kYevA9gwOe40xAjnOZmeH24qW0Aeesuc21gzO4DM1+fNikEjzHkQ609t6spwJrMp168x/jOx47w iLuinj8ZUYiBP2sxFQYgStBcRqVP3l1wlQtoeU3oOyMR5UX9vi3vHlqXjSTy0Ex+VbbX9AS5XUX STkQPWt0m0Q1q0Q== X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 Add a per-wb WB_DONTCACHE_DIRTY counter that tracks the number of dirty pages with the dropbehind flag set (i.e., pages dirtied via RWF_DONTCACHE writes). Increment the counter alongside WB_RECLAIMABLE in folio_account_dirtied() when the folio has the dropbehind flag set, and decrement it in folio_clear_dirty_for_io() and folio_account_cleaned(). Also decrement it when a non-DONTCACHE lookup clears the dropbehind flag on a dirty folio in __filemap_get_folio_mpol(), using proper writeback domain locking. The counter will be used by the writeback flusher to determine how many pages to write back when expediting writeback for IOCB_DONTCACHE writes, without flushing the entire BDI's dirty pages. Suggested-by: Jan Kara Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Jeff Layton --- include/linux/backing-dev-defs.h | 1 + mm/filemap.c | 13 ++++++++++++- mm/page-writeback.c | 6 ++++++ 3 files changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index a06b93446d10..cb660dd37286 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -33,6 +33,7 @@ enum wb_stat_item { WB_WRITEBACK, WB_DIRTIED, WB_WRITTEN, + WB_DONTCACHE_DIRTY, NR_WB_STAT_ITEMS }; diff --git a/mm/filemap.c b/mm/filemap.c index 4e636647100c..1c9c0d5f495f 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2052,8 +2052,19 @@ struct folio *__filemap_get_folio_mpol(struct address_space *mapping, if (!folio) return ERR_PTR(-ENOENT); /* not an uncached lookup, clear uncached if set */ - if (folio_test_dropbehind(folio) && !(fgp_flags & FGP_DONTCACHE)) + if (folio_test_dropbehind(folio) && !(fgp_flags & FGP_DONTCACHE)) { + if (folio_test_dirty(folio)) { + struct inode *inode = mapping->host; + struct bdi_writeback *wb; + struct wb_lock_cookie cookie = {}; + + wb = unlocked_inode_to_wb_begin(inode, &cookie); + wb_stat_mod(wb, WB_DONTCACHE_DIRTY, + -folio_nr_pages(folio)); + unlocked_inode_to_wb_end(inode, &cookie); + } folio_clear_dropbehind(folio); + } return folio; } EXPORT_SYMBOL(__filemap_get_folio_mpol); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 88cd53d4ba09..8e520717d1f6 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2630,6 +2630,8 @@ static void folio_account_dirtied(struct folio *folio, wb = inode_to_wb(inode); lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, nr); + if (folio_test_dropbehind(folio)) + wb_stat_mod(wb, WB_DONTCACHE_DIRTY, nr); __zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr); __node_stat_mod_folio(folio, NR_DIRTIED, nr); wb_stat_mod(wb, WB_RECLAIMABLE, nr); @@ -2651,6 +2653,8 @@ void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb) long nr = folio_nr_pages(folio); lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); + if (folio_test_dropbehind(folio)) + wb_stat_mod(wb, WB_DONTCACHE_DIRTY, -nr); zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); wb_stat_mod(wb, WB_RECLAIMABLE, -nr); task_io_account_cancelled_write(nr * PAGE_SIZE); @@ -2920,6 +2924,8 @@ bool folio_clear_dirty_for_io(struct folio *folio) if (folio_test_clear_dirty(folio)) { long nr = folio_nr_pages(folio); lruvec_stat_mod_folio(folio, NR_FILE_DIRTY, -nr); + if (folio_test_dropbehind(folio)) + wb_stat_mod(wb, WB_DONTCACHE_DIRTY, -nr); zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr); wb_stat_mod(wb, WB_RECLAIMABLE, -nr); ret = true; -- 2.54.0