Re: Getting PIDs out of inodes?

[Al Viro <viro@ZenIV.linux.org.uk>]

On Wed, Jan 15, 2014 at 04:08:01PM -0600, Ismael Farf??n wrote:
> Hello list.
> 
> I'm struggling with a problem involving some orphan descriptors I
> found in a crash dump.
> 
> I'd like to know who created or inherited (as in fork) them. I mustn't
> talk ill of the dead, but they are my prime suspects because of this
> (doesn't shows with ps):
> [49886.362859] umount.nfs[8425]: segfault at 19... bla bla
> 
> Given what I read[1,2], there doesn't seem to be a direct way to get
> the struct file (which contains a PID) out of the inode.

That makes no sense.  struct file does *not* contain a PID.

> I don't know if it's possible to script an iteration with crash over
> all tasks in search of a particular inode.
>      DENTRY           INODE       TYPE PATH
> ffff880936419900 ffff8808d17c5518 REG  foo.txt
> 
> Any ideas on how to know who created the file descriptors?

... and descriptor != struct file.  Moreover, if "who?" is "which process?",
it might have been dead, buried and its PID reused a long time ago - opened
file can easily outlive the process that had opened it.  What are you actually
trying to do?  Details, please...