• Vitaly Kuznetsov's avatar
    xen/blkback: unmap all persistent grants when frontend gets disconnected · c4221e3f
    Vitaly Kuznetsov authored
    commit 12ea7296 upstream.
    
    blkback does not unmap persistent grants when frontend goes to Closed
    state (e.g. when blkfront module is being removed). This leads to the
    following in guest's dmesg:
    
    [  343.243825] xen:grant_table: WARNING: g.e. 0x445 still in use!
    [  343.243825] xen:grant_table: WARNING: g.e. 0x42a still in use!
    ...
    
    When load module -> use device -> unload module sequence is performed multiple times
    it is possible to hit BUG() condition in blkfront module:
    
    [  343.243825] kernel BUG at drivers/block/xen-blkfront.c:954!
    [  343.243825] invalid opcode: 0000 [#1] SMP
    [  343.243825] Modules linked in: xen_blkfront(-) ata_generic pata_acpi [last unloaded: xen_blkfront]
    ...
    [  343.243825] Call Trace:
    [  343.243825]  [<ffffffff814111ef>] ? unregister_xenbus_watch+0x16f/0x1e0
    [  343.243825]  [<ffffffffa0016fbf>] blkfront_remove+0x3f/0x140 [xen_blkfront]
    ...
    [  343.243825] RIP  [<ffffffffa0016aae>] blkif_free+0x34e/0x360 [xen_blkfront]
    [  343.243825]  RSP <ffff88001eb8fdc0>
    
    We don't need to keep these grants if we're disconnecting as frontend might already
    forgot about them. Solve the issue by moving xen_blkbk_free_caches() call from
    xen_blkif_free() to xen_blkif_disconnect().
    
    Now we can see the following:
    [  928.590893] xen:grant_table: WARNING: g.e. 0x587 still in use!
    [  928.591861] xen:grant_table: WARNING: g.e. 0x372 still in use!
    ...
    [  929.592146] xen:grant_table: freeing g.e. 0x587
    [  929.597174] xen:grant_table: freeing g.e. 0x372
    ...
    
    Backend does not keep persistent grants any more, reconnect works fine.
    Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    c4221e3f
xenbus.c 22.9 KB