From: Jan Glauber <jglauber@digitalocean.com> commit 7abfabaf5f805f5171d133ce6af9b65ab766e76a upstream. Reading /proc/mdstat with a read buffer size that would not fit the unused status line in the first read will skip this line from the output. So 'dd if=/proc/mdstat bs=64 2>/dev/null' will not print something like: unused devices: <none> Don't return NULL immediately in start() for v=2 but call show() once to print the status line also for multiple reads. Cc: stable@vger.kernel.org Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface") Signed-off-by: Jan Glauber <jglauber@digitalocean.com> Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/md/md.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index e631550a8cf82..4406bb137a275 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7886,7 +7886,11 @@ static void *md_seq_start(struct seq_file *seq, loff_t *pos) loff_t l = *pos; struct mddev *mddev; - if (l >= 0x10000) + if (l == 0x10000) { + ++*pos; + return (void *)2; + } + if (l > 0x10000) return NULL; if (!l--) /* header */ -- 2.25.1