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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.
CC: stable@vger.kernel.org
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
12ea729645