linux-kernel - [PATCH v2 5/5] blk-iocost: read params inside lock in sysfs apis

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Message-Id: <20221104023938.2346986-6-yukuai1@huaweicloud.com>
Date:   Fri,  4 Nov 2022 10:39:38 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     hch@....de, tj@...nel.org, josef@...icpanda.com, axboe@...nel.dk,
        yukuai3@...wei.com
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai1@...weicloud.com,
        yi.zhang@...wei.com
Subject: [PATCH v2 5/5] blk-iocost: read params inside lock in sysfs apis

From: Yu Kuai <yukuai3@...wei.com>

Otherwise, user might get abnormal values if params is updated
concurrently.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-iocost.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 192ad4e0cfc6..7d682ce0bee6 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3135,6 +3135,7 @@ static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
 	if (!dname)
 		return 0;
 
+	mutex_lock(&ioc->params_mutex);
 	seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
 		   dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto",
 		   ioc->params.qos[QOS_RPPM] / 10000,
@@ -3147,6 +3148,7 @@ static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
 		   ioc->params.qos[QOS_MIN] % 10000 / 100,
 		   ioc->params.qos[QOS_MAX] / 10000,
 		   ioc->params.qos[QOS_MAX] % 10000 / 100);
+	mutex_unlock(&ioc->params_mutex);
 	return 0;
 }
 
@@ -3331,12 +3333,14 @@ static u64 ioc_cost_model_prfill(struct seq_file *sf,
 	if (!dname)
 		return 0;
 
+	mutex_lock(&ioc->params_mutex);
 	seq_printf(sf, "%s ctrl=%s model=linear "
 		   "rbps=%llu rseqiops=%llu rrandiops=%llu "
 		   "wbps=%llu wseqiops=%llu wrandiops=%llu\n",
 		   dname, ioc->user_cost_model ? "user" : "auto",
 		   u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
 		   u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]);
+	mutex_unlock(&ioc->params_mutex);
 	return 0;
 }
 
-- 
2.31.1