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 D0BF22DF9F; Tue, 20 Feb 2024 21:22:42 +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=1708464162; cv=none; b=I8RGpuptYsyZPKAODvWhLJ0s+8K9UMZvxc1YxmBM6rIn7a3tdEkX9i2umf8ktmWllgY+a8tr7ODztmIh4PhFgWDdtfKRiCmg3XmaTJlX0DdkB4KZdcPgfWmT9g4XxH3cZSnf6sYa6Trzdq84M0zzhH54VBpUC+2gvJrgiWnBZiY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708464162; c=relaxed/simple; bh=F5A9KnQqu0t2QMKvdXR/mHSZUP3Y2t3ly0YslMK2YnM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tGu7HW+anczO42uRRUOBCIDzdpZvsHqBF+sb5J10wTA/Q36tqt2iaRAlSjo/o5cdIAwEXdjeTayKvkLygOt1jaVMfgAqKTfUduNHa3MhaqACkwygn7MIMa/4ZXXEG4VBh20rtFwKclI3MWs3ecezAZjCUOlx23jHdToHW+f9uho= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gFKOaelv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gFKOaelv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EE78C433C7; Tue, 20 Feb 2024 21:22:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708464162; bh=F5A9KnQqu0t2QMKvdXR/mHSZUP3Y2t3ly0YslMK2YnM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gFKOaelvBasMiaKVjdgaTPTWQQ7XDPifnofngsCmGu1eDly8VD9EOr3IJUATz+Fhi ZpZKalUcAZzO7W2foInxy9uBtd7CXOi92nB28HghI0p+PgzGFF2tESVklg6hdj5stn v3vk/gFRf2zHsyL0JLLXRUgEJd83CeJOm8+FgKKM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Jens Axboe Subject: [PATCH 6.6 243/331] blk-wbt: Fix detection of dirty-throttled tasks Date: Tue, 20 Feb 2024 21:55:59 +0100 Message-ID: <20240220205645.440266432@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240220205637.572693592@linuxfoundation.org> References: <20240220205637.572693592@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit f814bdda774c183b0cc15ec8f3b6e7c6f4527ba5 upstream. The detection of dirty-throttled tasks in blk-wbt has been subtly broken since its beginning in 2016. Namely if we are doing cgroup writeback and the throttled task is not in the root cgroup, balance_dirty_pages() will set dirty_sleep for the non-root bdi_writeback structure. However blk-wbt checks dirty_sleep only in the root cgroup bdi_writeback structure. Thus detection of recently throttled tasks is not working in this case (we noticed this when we switched to cgroup v2 and suddently writeback was slow). Since blk-wbt has no easy way to get to proper bdi_writeback and furthermore its intention has always been to work on the whole device rather than on individual cgroups, just move the dirty_sleep timestamp from bdi_writeback to backing_dev_info. That fixes the checking for recently throttled task and saves memory for everybody as a bonus. CC: stable@vger.kernel.org Fixes: b57d74aff9ab ("writeback: track if we're sleeping on progress in balance_dirty_pages()") Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20240123175826.21452-1-jack@suse.cz [axboe: fixup indentation errors] Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-wbt.c | 4 ++-- include/linux/backing-dev-defs.h | 7 +++++-- mm/backing-dev.c | 2 +- mm/page-writeback.c | 2 +- 4 files changed, 9 insertions(+), 6 deletions(-) --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -165,9 +165,9 @@ static void wb_timestamp(struct rq_wb *r */ static bool wb_recent_wait(struct rq_wb *rwb) { - struct bdi_writeback *wb = &rwb->rqos.disk->bdi->wb; + struct backing_dev_info *bdi = rwb->rqos.disk->bdi; - return time_before(jiffies, wb->dirty_sleep + HZ); + return time_before(jiffies, bdi->last_bdp_sleep + HZ); } static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -141,8 +141,6 @@ struct bdi_writeback { struct delayed_work dwork; /* work item used for writeback */ struct delayed_work bw_dwork; /* work item used for bandwidth estimate */ - unsigned long dirty_sleep; /* last wait */ - struct list_head bdi_node; /* anchored at bdi->wb_list */ #ifdef CONFIG_CGROUP_WRITEBACK @@ -179,6 +177,11 @@ struct backing_dev_info { * any dirty wbs, which is depended upon by bdi_has_dirty(). */ atomic_long_t tot_write_bandwidth; + /* + * Jiffies when last process was dirty throttled on this bdi. Used by + * blk-wbt. + */ + unsigned long last_bdp_sleep; struct bdi_writeback wb; /* the root writeback info for this bdi */ struct list_head wb_list; /* list of all wbs */ --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -436,7 +436,6 @@ static int wb_init(struct bdi_writeback INIT_LIST_HEAD(&wb->work_list); INIT_DELAYED_WORK(&wb->dwork, wb_workfn); INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn); - wb->dirty_sleep = jiffies; err = fprop_local_init_percpu(&wb->completions, gfp); if (err) @@ -921,6 +920,7 @@ int bdi_init(struct backing_dev_info *bd INIT_LIST_HEAD(&bdi->bdi_list); INIT_LIST_HEAD(&bdi->wb_list); init_waitqueue_head(&bdi->wb_waitq); + bdi->last_bdp_sleep = jiffies; return cgwb_bdi_init(bdi); } --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1921,7 +1921,7 @@ pause: break; } __set_current_state(TASK_KILLABLE); - wb->dirty_sleep = now; + bdi->last_bdp_sleep = jiffies; io_schedule_timeout(pause); current->dirty_paused_when = now + pause;