From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792422450; b=HbR9Kn6E4KE2nsocudWYwF+MCAwsPP+q6HRF4TXq9d9WDOWjM9uSiygixVVf8jGRDcEs Rd2kyKXnRuSNatQBR6GohrnK1DCd7GT7U20dKYs5Fe0xNKbknR2SpwFB3osUPuSNjs51q hu0lwPlCVSk1YfFD3T6Gx4Zlq1lTrD/ryuKeCUQ5vGdaoKd9n2oIhhDLTrHJXhbi1CoyT ZhGcisx5R1zetJlDd6Cm2fQZXK0bJbAgTOjm1CFZWV0QoIajOH9C7kxGtOai7ItQ3EwY/ GFk7L2l+yXYz0kwY03qgVSCZKbqkqRfvlw+EYh942Bdvt2DfkycSjf5sBb1OJ5ZHrWA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792422450; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=KYIFZnbJ/tQXvMmHyoqaiwEU9dnEoX51wTobPwpbUYk=; b=MAyylYJx2KEkGmAg2agDowo2Ujn/ZkCx6AoHlMQnxqKcg6i0/ZDX/S5DBi45jIV/zsau JIiT/+Afx0ySx1W/ZVjLnNozSZOma6oGdPtQP+QIzR1JyEOvm7Wl/GZVmL7EbBtCx/w3E m1a/ZjaXWc07zVICMxWqzLY6rIf1NiKeKs3XvmAh1qcugtfXue0ZP1hbXa02MM0uFmXiP VnFw432mMUbUYPw2W1XMAB2WFUXcFj0FcjkjZ6ovbCPCqL3ZgHZOKV96xLtVdGBEdKXLt 1TvxCPfkBR4vVqJo+ogA5XknnBuFAdnN2GjYeiIYFpDP7qZIcOzvqFM5qK2aH+xaHTw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="Q7/5HC2y"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B68036083439; Mon, 19 Oct 2026 15:07:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Q7/5HC2y Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EE711F000C4; Mon, 19 Oct 2026 15:07:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792422449; bh=KYIFZnbJ/tQXvMmHyoqaiwEU9dnEoX51wTobPwpbUYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Q7/5HC2yuwRStW9uT0uRx6ddM3dspudm2S30vTdZhfxrJmdHNXGuppUxH6i1DtdhH XjJjNTLHPLxrW+qWvrEpd8QN+onnmwyIgNnBd0fQwuSdK92xPdtwMt1w7M4+Xwq/mn f2iPBxoQzG7PyD7Pe9C0ddHHi4/2k5vc/xBQBeN3Jth1U9QUpRRAYBhKd3j951VokQ /sZR+wL4hUIgfRCuk/OZ791Cf+jBc8dVRwgXpTXGpeKjA+vV2F30ax7BGlHDmLNjPB QO4zLIX/y1ygzGKb0ZtRKtxszT+/Cz4bUJLMDo/w8DN5pAkzhrfg/g0lPdI+dMDHY4 K/2eHdhpPreFw== From: Mike Snitzer To: Chuck Lever , Jeff Layton Cc: linux-nfs@vger.kernel.org, NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , Christoph Hellwig , Jens Axboe , Matthew Wilcox , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v5 2/6] mm: expose WB_DONTCACHE_DIRTY in bdi debugfs stats Date: Mon, 19 Oct 2026 11:07:21 -0400 Message-ID: <20261019150725.1507-3-snitzer@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20261019150725.1507-1-snitzer@kernel.org> References: <20261019150725.1507-1-snitzer@kernel.org> X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The per-bdi_writeback WB_DONTCACHE_DIRTY counter drives how much the flusher writes back in response to an IOCB_DONTCACHE kick, but it is not reported anywhere, so the DONTCACHE dirty backlog can only be inferred from MemFree/Cached movement. Report it as BdiDontcacheDirty in /sys/kernel/debug/bdi//stats and as WbDontcacheDirty in the per-wb stats, next to the Reclaimable line. Use wb_stat_sum() rather than wb_stat() to fold in the per-cpu batches: the flusher targets the summed value and small backlogs would otherwise read as zero. Fixes: 88d6f128d06d ("mm: track DONTCACHE dirty pages per bdi_writeback") Cc: Jeff Layton Cc: Jens Axboe Cc: Matthew Wilcox (Oracle) Cc: linux-mm@kvack.org Assisted-by: LLM Signed-off-by: Mike Snitzer --- mm/backing-dev.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 18e999053bae..b8a2c27e07fa 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -46,6 +46,7 @@ struct wb_stats { unsigned long nr_dirty_time; unsigned long nr_writeback; unsigned long nr_reclaimable; + unsigned long nr_dontcache_dirty; unsigned long nr_dirtied; unsigned long nr_written; unsigned long dirty_thresh; @@ -78,6 +79,12 @@ static void collect_wb_stats(struct wb_stats *stats, stats->nr_writeback += wb_stat(wb, WB_WRITEBACK); stats->nr_reclaimable += wb_stat(wb, WB_RECLAIMABLE); + /* + * Sum the per-cpu batches: the dontcache flusher targets this + * counter via wb_stat_sum() and small backlogs would otherwise + * read as zero here. + */ + stats->nr_dontcache_dirty += wb_stat_sum(wb, WB_DONTCACHE_DIRTY); stats->nr_dirtied += wb_stat(wb, WB_DIRTIED); stats->nr_written += wb_stat(wb, WB_WRITTEN); stats->wb_thresh += wb_calc_thresh(wb, stats->dirty_thresh); @@ -125,6 +132,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) seq_printf(m, "BdiWriteback: %10lu kB\n" "BdiReclaimable: %10lu kB\n" + "BdiDontcacheDirty: %10lu kB\n" "BdiDirtyThresh: %10lu kB\n" "DirtyThresh: %10lu kB\n" "BackgroundThresh: %10lu kB\n" @@ -139,6 +147,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) "state: %10lx\n", K(stats.nr_writeback), K(stats.nr_reclaimable), + K(stats.nr_dontcache_dirty), K(stats.wb_thresh), K(dirty_thresh), K(background_thresh), @@ -163,6 +172,7 @@ static void wb_stats_show(struct seq_file *m, struct bdi_writeback *wb, "WbCgIno: %10lu\n" "WbWriteback: %10lu kB\n" "WbReclaimable: %10lu kB\n" + "WbDontcacheDirty: %10lu kB\n" "WbDirtyThresh: %10lu kB\n" "WbDirtied: %10lu kB\n" "WbWritten: %10lu kB\n" @@ -179,6 +189,7 @@ static void wb_stats_show(struct seq_file *m, struct bdi_writeback *wb, #endif K(stats->nr_writeback), K(stats->nr_reclaimable), + K(stats->nr_dontcache_dirty), K(stats->wb_thresh), K(stats->nr_dirtied), K(stats->nr_written), -- 2.52.0