On 27/09/18 16:26, Jens Axboe wrote:
> On 9/27/18 1:12 AM, Juergen Gross wrote:
>> On 22/09/18 21:55, Boris Ostrovsky wrote:
>>> Commit a46b53672b2c ("xen/blkfront: cleanup stale persistent grants")
>>> added support for purging persistent grants when they are not in use. As
>>> part of the purge, the grants were removed from the grant buffer, This
>>> eventually causes the buffer to become empty, with BUG_ON triggered in
>>> get_free_grant(). This can be observed even on an idle system, within
>>> 20-30 minutes.
>>>
>>> We should keep the grants in the buffer when purging, and only free the
>>> grant ref.
>>>
>>> Fixes: a46b53672b2c ("xen/blkfront: cleanup stale persistent grants")
>>> Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
>>
>> Reviewed-by: Juergen Gross <jgr...@suse.com>
>
> Since Konrad is out, I'm going to queue this up for 4.19.
>
Hi Boris/Juergen.
Last week i tested a linux-4.19-rc4 kernel with xen-next and this patch from
Boris pulled on top.
Unfortunately it made a VM hang (probably because it's rootFS is shuffled from
under it's feet
and it gave these in dom0 dmesg:
[ 9251.696090] xen-blkback: requesting a grant already in use
[ 9251.705861] xen-blkback: trying to add a gref that's already in the tree
[ 9251.715781] xen-blkback: requesting a grant already in use
[ 9251.725756] xen-blkback: trying to add a gref that's already in the tree
[ 9251.735698] xen-blkback: requesting a grant already in use
[ 9251.745573] xen-blkback: trying to add a gref that's already in the tree
The VM was a HVM with 4 vcpu's and 2 phy disks:
xen-blkback: backend/vbd/14/768: using 4 queues, protocol 1 (x86_64-abi)
persistent grants
xen-blkback: backend/vbd/14/832: using 4 queues, protocol 1 (x86_64-abi)
persistent grants
Currently i have been running 4.19-rc5 with xen-next on top and commit
a46b53672b2c reverted,
for a couple of days. That seems to run stable for me (since it's a small box
so i'm not hit
by what a46b53672b2c tried to fix.
If you can come up with a debug patch i can give that a spin tomorrow evening
or in the weekend,
so we are hopefully still in time for the 4.19 release.
--
Sander
