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 9C2833CF683; Tue, 5 May 2026 19:00:15 +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=1778007615; cv=none; b=LJyiaDOA3c9DeAQhEGYpNkEzkBkS0gNdB7tgYhCFO0yjMteGvYRWURgC5/p+/8BLwAIcwEVqOoy3w9z1QhF+Uc0H8YFqbhbqREmPraAjJ8M5HiddSB7wyC5KPxrg/v/9mQ9H1+XlMDuiuWT4R5uV+tcu4zKZggAiphILoelc5cc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778007615; c=relaxed/simple; bh=VNFDaVKtHxfKb5Jtg4lw1jtyfG4WqayLBxu+KyjdETI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=S7cckYrJs7R3Chl6LlXbaSu/Hv0C3viu1Oq5cl8cVxWEFD3NvzuYPTGxez8vtevKjnOQ/sSB/Wv/JV5uEEkl46+FvWo+ghpK4cReX+Smioi9Itg7nTjZ5ZfbYXF+GWXrjK2JlRYcBBA0/yihBJ2j5SQXRQEWrC0eD9zx1jAMKzM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F/63nRja; 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="F/63nRja" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61ED1C2BCB4; Tue, 5 May 2026 19:00:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778007615; bh=VNFDaVKtHxfKb5Jtg4lw1jtyfG4WqayLBxu+KyjdETI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=F/63nRjaUCMUeXblGr32PcC5EvgwHVUSYc2KMVZZYd2AXLUXRg2vrU7OOiweSLmAz Ey0FQDJuRcYeSomo5C5yHitaEH34lItP6ooE5ardeEA4zoOkaQsQn4hg25KW3VqH3H f4vrxfBzb6VdxbtSQOm1UjWHWhEE5K5kgS5TFbyk15gvR3GTdAGvB0bUxXNsHOHlkT a7aKqpIl1NlQb0kWuBjSk1XEpHZVbro8qsNRNIzDG4gs0OmPtwUAQ1ZNin4IC0RxRY 1UEXhZuejm2V4wu+l0u/WfRB0cI954NwGaD2b8hKlJ4Ix1ncWVYdVzw41T0Lc7qSQ5 3XwrkjU1fJeaw== From: Jeff Layton Date: Tue, 05 May 2026 20:59:48 +0200 Subject: [PATCH v6 1/2] 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: <20260505-dontcache-v6-1-66463805dd6a@kernel.org> References: <20260505-dontcache-v6-0-66463805dd6a@kernel.org> In-Reply-To: <20260505-dontcache-v6-0-66463805dd6a@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=3898; i=jlayton@kernel.org; h=from:subject:message-id; bh=VNFDaVKtHxfKb5Jtg4lw1jtyfG4WqayLBxu+KyjdETI=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBp+j4zKs26S/A9Ogbbp0fUGJuKz7QkA8Ss6E16g 9ZgN8VzOGiJAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCafo+MwAKCRAADmhBGVaC FbHuEAClfB9yntbp0VqHfI94dQPxUMse8RDGZxSS7rytsC1YCO6tM8EOs6PSMXyZ5zGp8ZijYGk 4MnLilXhL2s6P9YBhrdC3RfRbKcbiY+vtny8oGucvHnEe7Q8MjdUjp31AcAkN0/DhLYYz/jKT/Y ctlkhyan7088mUgwwL7jVVdlht6dnp7XEhkNya332Q3tgcffiR2NUUFPY4sorFpkcgkpnypI1tL GKhmT+XvPQ/kPeq4d+RfWWe/lJNUGtmU1zgSLJ2RBgrDPkxVOESrzcTVvVjb8gYcjLmmmJqsTzz 1NGInwei02fIoO79WpaXalTDTNO75+NcCQf+DKjjhX2Ln0e8/LvlGFbr3mYraTuPNBXMw7gMrrc 5qxd/cM4ruPr5HdoQm8Bn64wdbW3trY9nY8wvb6A6sqbgQbWrXoOAAi3lpv1H2239YovXFBVeA2 5rWA4tV9zc6cNm4++YD7SA1nR9DeEBItq996hWr89i1WRFgXf6R7Wzw5lEaySOJyBEc1d3zUuLR y7+OPc5GMP2p6KjtjjCjovc8GhSyUZ5gdRS6EoKbYh5/R54ypCSxCXmWPHnnXBELS4VmAABQ+8Z 40tCPbgSmoTKbXnnGurViHDMlpEsnvU/NF8CREIG1YGk1MBneldUdDzSDYk4nsvHFO0NiZmfMTb AVtn8Wx8tKTA5Jw== 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 atomically clears the dropbehind flag on a dirty folio in __filemap_get_folio_mpol(), using folio_test_clear_dropbehind() to prevent concurrent lookups from double-decrementing the counter, and guarding the decrement with mapping_can_writeback() to match the increment path. 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 | 15 +++++++++++++-- mm/page-writeback.c | 6 ++++++ 3 files changed, 20 insertions(+), 2 deletions(-) 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..e706f5c4ece4 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)) - folio_clear_dropbehind(folio); + if (!(fgp_flags & FGP_DONTCACHE) && folio_test_clear_dropbehind(folio)) { + if (folio_test_dirty(folio) && + mapping_can_writeback(mapping)) { + 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); + } + } 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