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Re: [PATCH] configfs: Fix race between create_link and configfs_rmdir

From "Nicholas A. Bellinger" <nab@linux-iscsi.org>
Newsgroups linux.kernel
Subject Re: [PATCH] configfs: Fix race between create_link and configfs_rmdir
Date 2017-06-09 09:10 +0200
Message-ID <tQmdt-6TG-27@gated-at.bofh.it> (permalink)
References <tPXyp-801-1@gated-at.bofh.it> <tQ03g-1dY-17@gated-at.bofh.it> <tQ4Tg-4hK-23@gated-at.bofh.it>
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On Thu, 2017-06-08 at 07:34 -0500, Bryant G. Ly wrote:
> > Thanks Nic,
> >
> > applied to the configfs-for-next tree.  I'm not entirely sure if we
> > should bother adding this to 4.12 or if it hits rarely enough?
> >
> It hits for us pretty often when we have a GPFS setup with 10 hosts and 1k+ vms.
> 
> That is how we discovered the bug in the first place.
> 

Using a DATERA workload with 1K unique multi-tenant backend devices and
1K unique iscsi-target IQNs per node, I've never tripped across this
particular bug..

However, our userspace built atop rtslib is enforcing tenant shutdown of
individual rmdir(2) of /sys/kernel/config/target/$FABRIC/$WWN/$TPGT/,
before rmdir(2) of /sys/kernel/config/target/core/$HBA/$DEV/ occurs.

Based on Bryant's original backtrace with targetcli, it looks like the
Novalink user-space is not enforcing this requirement across user-space
processes doing fabric port symlink and backend device shutdown.

That said it probably doesn't need a special v4.12-rc PULL, but based on
Bryant's feedback it certainly does deserve a stable CC'.

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Thread

[PATCH] configfs: Fix race between create_link and configfs_rmdir "Nicholas A. Bellinger" <nab@linux-iscsi.org> - 2017-06-08 06:50 +0200
  Re: [PATCH] configfs: Fix race between create_link and         configfs_rmdir Christoph Hellwig <hch@lst.de> - 2017-06-08 09:30 +0200
    Re: [PATCH] configfs: Fix race between create_link and configfs_rmdir "Bryant G. Ly" <bryantly@linux.vnet.ibm.com> - 2017-06-08 14:40 +0200
      Re: [PATCH] configfs: Fix race between create_link and  configfs_rmdir "Nicholas A. Bellinger" <nab@linux-iscsi.org> - 2017-06-09 09:10 +0200

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