On Thu, Aug 12, 2004 at 11:02:51AM -0700, Mike Christie wrote: > around through remapper drivers like we do with bios, or should we avoid > the mess and goto userspace (with userspace there would have to be a way > to properly traverse mappers too though)? Are there issues with issuing an SG_IO from user space when we are out of memory? That is we have: sg_io -> blk_rq_map_user -> if aligned bio_map_user, else bio_copy_user Both bio_*_user do a bio_alloc GFP_KERNEL, and bio_copy_user also has an alloc_page GFP_KERNEL. So when trying to reclaim memory or such, if we are writing to a multipathed device, and it fails and requires a failover command to be sent, the user space SG_IO kernel allocation could sleep, and the system would hang. Could we somehow avoid those? We might still have issues with requiring a user process in memory for each path that might need to failover (just that there might be a good number of them with a large number of disks), but that does not seem bad. -- Patrick Mansfield
