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Date:   Thu, 21 May 2020 12:30:55 +1000
From:   Craig Small <csmall@dropbear.xyz>
To:     linux-nfs@vger.kernel.org
Subject: How to separate NFS mounts have same device ID
Message-ID: <20200521023055.GA1246587@dropbear.xyz>
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Hi,
  I'm the author of the psmisc programs that include things like killall and fuser.  I have a problem with finding files open on NFS mounts from the same server.  The issue is at https://gitlab.com/psmisc/psmisc/-/issues/10

The way fuser does its job is to find the mounts you specify and collect the device IDs, then scans all /proc/<PID/fd/* for matching devices. However, NFS mounts from the same server have the same device ID so fuser reports every mount has the same file opened.

Putting it another way, if I said "here is file /proc/<PID>/fd/3, dereference the symlink and tell me which of these two NFS mounts from the same server it comes from?" how would you do it?
A simple string match (/mnt/a vs /mnt/b) does not work because you can have symlinks across mounts.

Any help here would be appreciated. I'm not subscribed to the list so hopefully, this makes it through whatever filters there are and please CC me on replies.

 - Craig