linux-kernel - DAX can not work on virtual nvdimm device

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Date:   Fri, 19 Aug 2016 19:19:20 +0800
From:   Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        KVM <kvm@...r.kernel.org>,
        "Zhang, Haozhong" <haozhong.zhang@...el.com>,
        Yumei Huang <yuhuang@...hat.com>
Subject: DAX can not work on virtual nvdimm device


Hi Dan,

Recently, Redhat reported that nvml test suite failed on QEMU/KVM,
more detailed info please refer to:
    https://bugzilla.redhat.com/show_bug.cgi?id=1365721

The reason for this bug is that the memory region created by mmap()
on the dax-based file was gone so that the region can not be found
in /proc/self/smaps during the runtime.

This is a simple way to trigger this issue:
    mount -o dax /dev/pmem0 /mnt/pmem/
    vim /mnt/pmem/xxx
then 'vim' is crashed due to segment fault.

This bug can be reproduced on your tree, the top commit is
10d7902fa0e82b (dax: unmap/truncate on device shutdown), the kernel
configure file is attached.

Your thought or comment is highly appreciated.

Thanks!


View attachment "config-dax" of type "text/plain" (145456 bytes)