On Thu, 8 Aug 2019, Matthew Wilcox wrote: > On Thu, Aug 08, 2019 at 05:50:10AM -0400, Mikulas Patocka wrote: > > A deadlock with this stacktrace was observed. > > > > The obvious problem here is that in the call chain > > xfs_vm_direct_IO->__blockdev_direct_IO->do_blockdev_direct_IO->kmem_cache_alloc > > we do a GFP_KERNEL allocation while we are in a filesystem driver and in a > > block device driver. > > But that's not the problem. The problem is the loop driver calls into the > filesystem without calling memalloc_noio_save() / memalloc_noio_restore(). > There are dozens of places in XFS which use GFP_KERNEL allocations and > all can trigger this same problem if called from the loop driver. OK. I'll send a new patch that sets PF_MEMALLOC_NOIO in the loop driver. Mikulas
