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Message-Id: <20190724191718.218353974@linuxfoundation.org>
Date: Wed, 24 Jul 2019 21:22:17 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Tejun Heo <tj@...nel.org>,
Josef Bacik <jbacik@...com>, Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.19 268/271] blkcg: update blkcg_print_stat() to handle larger outputs
From: Tejun Heo <tj@...nel.org>
commit f539da82f2158916e154d206054e0efd5df7ab61 upstream.
Depending on the number of devices, blkcg stats can go over the
default seqfile buf size. seqfile normally retries with a larger
buffer but since the ->pd_stat() addition, blkcg_print_stat() doesn't
tell seqfile that overflow has happened and the output gets printed
truncated. Fix it by calling seq_commit() w/ -1 on possible
overflows.
Signed-off-by: Tejun Heo <tj@...nel.org>
Fixes: 903d23f0a354 ("blk-cgroup: allow controllers to output their own stats")
Cc: stable@...r.kernel.org # v4.19+
Cc: Josef Bacik <jbacik@...com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
block/blk-cgroup.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1016,8 +1016,12 @@ static int blkcg_print_stat(struct seq_f
}
next:
if (has_stats) {
- off += scnprintf(buf+off, size-off, "\n");
- seq_commit(sf, off);
+ if (off < size - 1) {
+ off += scnprintf(buf+off, size-off, "\n");
+ seq_commit(sf, off);
+ } else {
+ seq_commit(sf, -1);
+ }
}
}
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