linux-kernel - [PATCH 4/4] blk-throttle: Fix IO hang for a corner case

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Date:   Sun, 20 Sep 2020 17:14:27 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     tj@...nel.org, axboe@...nel.dk
Cc:     baolin.wang@...ux.alibaba.com, baolin.wang7@...il.com,
        linux-block@...r.kernel.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] blk-throttle: Fix IO hang for a corner case

It can not scale up in throtl_adjusted_limit() if we set bps or iops is
1, which will cause IO hang when enable low limit. Thus we should treat
1 as a illegal value to avoid this issue.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 block/blk-throttle.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index b0d8f7c..0649bce 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1687,13 +1687,13 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 			goto out_finish;
 
 		ret = -EINVAL;
-		if (!strcmp(tok, "rbps"))
+		if (!strcmp(tok, "rbps") && val > 1)
 			v[0] = val;
-		else if (!strcmp(tok, "wbps"))
+		else if (!strcmp(tok, "wbps") && val > 1)
 			v[1] = val;
-		else if (!strcmp(tok, "riops"))
+		else if (!strcmp(tok, "riops") && val > 1)
 			v[2] = min_t(u64, val, UINT_MAX);
-		else if (!strcmp(tok, "wiops"))
+		else if (!strcmp(tok, "wiops") && val > 1)
 			v[3] = min_t(u64, val, UINT_MAX);
 		else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
 			idle_time = val;
-- 
1.8.3.1