[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/blkfront: When purging persistent grants, keep them in the buffer
On 9/27/18 12:52 PM, Sander Eikelenboom wrote: > 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.ostrovsky@xxxxxxxxxx> >>> >>> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> >> >> 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. At this late in the game, might make more sense to simply revert the buggy commit. Especially since what is currently out there doesn't fix the issue for you. -- Jens Axboe _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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