[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 5:37 PM, Jens Axboe wrote: > On 9/27/18 2:33 PM, Sander Eikelenboom wrote: >> On 27/09/18 21:06, Boris Ostrovsky wrote: >>> On 9/27/18 2:56 PM, Jens Axboe wrote: >>>> 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 >>> What do you mean by "rootFS is shuffled from under it's feet " ? >> Assumption that block-front getting borked and either a kernel crash or >> rootfs becoming mounted readonly. Didn't (try) to check though. >> >>>>> 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. >> Don't know if Boris or Juergen have a hunch about the issue, if not >> perhaps a revert is the best. > Anyone? Unless I hear otherwise, I'll revert the series tomorrow. Juergen may have something to say by tomorrow, but from my perspective, given that we are coming up on rc6 --- yes. I looked at the patches again and didn't see anything obvious. -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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