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 15CA5378D71; Mon, 4 May 2026 13:21:28 +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=1777900888; cv=none; b=tDzY43VFzodLtmMH4WgLfseW6tm4R1jG5ZVo87MRP6AWh8ROURDBegDrk0fGdBDZO+KsFilb1+Z0EmO7sgz7VpwiT/NViGjqORKztywnLXT6lJA5e0O9UvYqBAjocm7Q4p9ryWwpGbGFfeTMq3crephHSrAi5WgboT7G4WKlETQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777900888; c=relaxed/simple; bh=2aFCrdi086X8qaY+nrQYNcsSeV5HvIWfW7LHiwbQchQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=taiYiqx1/F8qC5UvkZMGh/JjlnSFwvUKTD1hA7bJhH3TyoK2BKlyuX++S23G4zjZnvkP/EqOip2KggoyP7X9sGAUZM/WoLml1bJYd3/CV9X5c7AnT1xVz9mz6eVEVTHb8+X9kOEaEkr55OM/ov4xI5vt+jOjb94PBvb01Dw0VIY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cmW1qlBQ; 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="cmW1qlBQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34274C4AF09; Mon, 4 May 2026 13:21:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777900887; bh=2aFCrdi086X8qaY+nrQYNcsSeV5HvIWfW7LHiwbQchQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=cmW1qlBQq1HOb3cm9DFTA9YWVwxGTYZ/7TDKbbF+u0tf0t0+vmPZw2hBkA+K8gxOI aFjZC9Igr0Kf7wNgdzLmEu0yIwOhPPkmhQ8RFdE3H2G2BEGqdpjlihBLjHCyZz113T PiFHPjWRTNQX64T+kzdNYo+BBay/WjHds/NBI2nIcopTuune73KPhKIKkdH8mnSt8/ mWaYsErFDGhpJx8I0j/uDTXjt6v4duueKgk3bKYpmzwD3JCDga8OjnPWjxEiVA1RkD 2finvn/5LM7g6+uSv+LuaUVfnrwlvhMv1DLRHIM4l+29nGQUfcQTbU6d/ysSVMKGXH Ujiab4Xt/9Ikg== From: Jeff Layton Date: Mon, 04 May 2026 15:20:49 +0200 Subject: [PATCH v5 1/2] mm: track DONTCACHE dirty pages per bdi_writeback Precedence: bulk X-Mailing-List: linux-nfs@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: <20260504-dontcache-v5-1-4103e58bb377@kernel.org> References: <20260504-dontcache-v5-0-4103e58bb377@kernel.org> In-Reply-To: <20260504-dontcache-v5-0-4103e58bb377@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=3721; i=jlayton@kernel.org; h=from:subject:message-id; bh=2aFCrdi086X8qaY+nrQYNcsSeV5HvIWfW7LHiwbQchQ=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBp+J1NRZKbyI7QhGLiFF2oAvXgvp74opb+1ER2w V1/zzRaInuJAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCafidTQAKCRAADmhBGVaC FVfRD/43QS9dZ/TF2zC6q4G6CqPoyA3ARP6obj1Xj+LbLpvyEmgsXxz+3d+U/FfnrA8BRHtb9QL qr+DcoUZk2qB+URtNgCPYPwKBDtqkgJ+SisKUHuXzqjw3qMTh6c4znnSG633tJttJopxbpR8YII s7t5olXjXb4eEmwPXIRAKzfrnxHBIj9WN9NZpWIKHDuQP529fBhbZEVyOnxorJuYKUebcLYerxm ha+rmiV4D17PNqIyUeX5rYbvKeeD3bUuXCQ1H+qI580RjMfbgUlisrWaK9vh7m+wB90snPQvcYQ dS9oFMbTspr49VuAUf/VEl6sFBgEllf+GwuujzQBWomgFJDCCM/xpeb1pRfc28ciMhTMzRD6lxq nLBiUtrwSR1UfOoruRdfA4PYDPsB6vFq5hNZMxgWhyJXgTrJhUif2Vzg+ADwlUMZfL49Xa1hYbu TS6q9Ph5QR+x1q7QaWGrax44oyb25sS7eRWljcso6CLFZU9EOrc6hoxEHFQyZpzVimCExJVFSkD BA8N0u5a9Wb27puAE8r2v0xFcGhZqf2qBiMZuTWNiiJ6csZBaeuvziWe+ESXIgabtB82LDJjkIm 8DUcz0KpgvQYgTixhjkclRiF/6xqWnRG0G1EZ/CFfKBjt11N2Fd9F7enrpPODrT2CWcHbqoQuKr zLenDJ+Xa6OU7GQ== 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 Reviewed-by: Jan Kara 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