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From:   Kenneth D'souza <kdsouza@redhat.com>
To:     linux-nfs@vger.kernel.org
Cc:     kdsouza@redhat.com, SteveD@redhat.com
Subject: [PATCH] nfs-iostat: divide by zero with fresh mount
Date:   Mon, 24 Aug 2020 20:35:35 +0530
Message-Id: <20200824150535.15224-1-kdsouza@redhat.com>
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Sender: linux-nfs-owner@vger.kernel.org
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When an export is freshly mounted, /proc/self/mountstats displays age = 0.
This causes nfs-iostat to divide by zero throwing an error.
When we have age = 0, other stats are greater than 0, so we'll set age = 1 and
print the relevant stats.

This will prevent a backtrace like this from occurring if nfsiostat is run.

nfsiostat -s 1
Traceback (most recent call last):
  File "/usr/sbin/nfsiostat", line 662, in <module>
    iostat_command(prog)
  File "/usr/sbin/nfsiostat", line 644, in iostat_command
    print_iostat_summary(old_mountstats, mountstats, devices, sample_time, options)
  File "/usr/sbin/nfsiostat", line 490, in print_iostat_summary
    devicelist.sort(key=lambda x: stats[x].ops(time), reverse=True)
  File "/usr/sbin/nfsiostat", line 490, in <lambda>
    devicelist.sort(key=lambda x: stats[x].ops(time), reverse=True)
  File "/usr/sbin/nfsiostat", line 383, in ops
    return (sends / sample_time)
ZeroDivisionError: float division by zero

Signed-off-by: Kenneth D'souza <kdsouza@redhat.com>
---
 tools/nfs-iostat/nfs-iostat.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/nfs-iostat/nfs-iostat.py b/tools/nfs-iostat/nfs-iostat.py
index 5556f692..0c6c6dda 100755
--- a/tools/nfs-iostat/nfs-iostat.py
+++ b/tools/nfs-iostat/nfs-iostat.py
@@ -383,6 +383,8 @@ class DeviceData:
         sends = float(self.__rpc_data['rpcsends'])
         if sample_time == 0:
             sample_time = float(self.__nfs_data['age'])
+        if sample_time == 0:
+            sample_time = 1;
         return (sends / sample_time)
 
     def display_iostats(self, sample_time, which):
-- 
2.21.3