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blkcg: update blkcg_print_stat() to handle larger outputs

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commit f539da82f2 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@kernel.org>
Fixes: 903d23f0a3 ("blk-cgroup: allow controllers to output their own stats")
Cc: stable@vger.kernel.org # v4.19+
Cc: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2019-06-13 15:30:38 -07:00 committed by Greg Kroah-Hartman
parent 73efdc5d7d
commit dd87cc633b
1 changed files with 6 additions and 2 deletions
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8
block/blk-cgroup.c
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@ -1016,8 +1016,12 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
}
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);
}
}
}