• Roger Pau Monne's avatar
    xen/blkback: free requests on disconnection · f929d42c
    Roger Pau Monne authored
    This is due to  commit 86839c56
    "xen/block: add multi-page ring support"
    
    When using an guest under UEFI - after the domain is destroyed
    the following warning comes from blkback.
    
    ------------[ cut here ]------------
    WARNING: CPU: 2 PID: 95 at
    /home/julien/works/linux/drivers/block/xen-blkback/xenbus.c:274
    xen_blkif_deferred_free+0x1f4/0x1f8()
    Modules linked in:
    CPU: 2 PID: 95 Comm: kworker/2:1 Tainted: G        W       4.2.0 #85
    Hardware name: APM X-Gene Mustang board (DT)
    Workqueue: events xen_blkif_deferred_free
    Call trace:
    [<ffff8000000890a8>] dump_backtrace+0x0/0x124
    [<ffff8000000891dc>] show_stack+0x10/0x1c
    [<ffff8000007653bc>] dump_stack+0x78/0x98
    [<ffff800000097e88>] warn_slowpath_common+0x9c/0xd4
    [<ffff800000097f80>] warn_slowpath_null+0x14/0x20
    [<ffff800000557a0c>] xen_blkif_deferred_free+0x1f0/0x1f8
    [<ffff8000000ad020>] process_one_work+0x160/0x3b4
    [<ffff8000000ad3b4>] worker_thread+0x140/0x494
    [<ffff8000000b2e34>] kthread+0xd8/0xf0
    ---[ end trace 6f859b7883c88cdd ]---
    
    Request allocation has been moved to connect_ring, which is called every
    time blkback connects to the frontend (this can happen multiple times during
    a blkback instance life cycle). On the other hand, request freeing has not
    been moved, so it's only called when destroying the backend instance. Due to
    this mismatch, blkback can allocate the request pool multiple times, without
    freeing it.
    
    In order to fix it, move the freeing of requests to xen_blkif_disconnect to
    restore the symmetry between request allocation and freeing.
    Reported-by: default avatarJulien Grall <julien.grall@citrix.com>
    Signed-off-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
    Tested-by: default avatarJulien Grall <julien.grall@citrix.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: David Vrabel <david.vrabel@citrix.com>
    Cc: xen-devel@lists.xenproject.org
    CC: stable@vger.kernel.org # 4.2
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    f929d42c
xenbus.c 24.7 KB