From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] IB/srp: Process REQ_PREEMPT requests correctly Date: Fri, 30 Jan 2015 14:18:59 -0600 Message-ID: <54CBE733.9000004@cs.wisc.edu> References: <54CA2F48.605@sandisk.com> <54CA8C4C.1080508@cs.wisc.edu> <54CAE71C.6020002@cs.wisc.edu> <54CB9670.6080108@sandisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54CB9670.6080108-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche Cc: Roland Dreier , Max Gurtuvoy , Sagi Grimberg , linux-rdma , "linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On 01/30/2015 08:34 AM, Bart Van Assche wrote: > On 01/30/15 03:06, Mike Christie wrote: >> I think I figured this out. I think we want to change the >> scsi_prep_state_check check instead of each driver/class. >> >> It looks like for the SDEV_QUIESCE state we want to allow REQ_PREEMPT >> commands. James would know best, but I think SPI needs that ability. >> >> For SDEV_BLOCK/SDEV_CREATED_BLOCK, it looks like drivers/classes that >> use that state do not want any commands to be queued at that time, >> because the transport is normally down. > > Hello Mike, > > Is something like the patch below what you had in mind ? > > Bart. > > [PATCH] Defer processing of REQ_PREEMPT requests for blocked devices > > SCSI transport drivers and SCSI LLDs block a SCSI device if the > transport layer is not operational. This means that in this state > no requests should be processed, even if the REQ_PREEMPT flag has > been set. This patch avoids that a rescan shortly after a cable > pull sporadically triggers the following kernel oops: > > BUG: unable to handle kernel paging request at ffffc9001a6bc084 > IP: [] mlx4_ib_post_send+0xd2/0xb30 [mlx4_ib] > Process rescan-scsi-bus (pid: 9241, threadinfo ffff88053484a000, task ffff880534aae100) > Call Trace: > [] srp_post_send+0x65/0x70 [ib_srp] > [] srp_queuecommand+0x1cf/0x3e0 [ib_srp] > [] scsi_dispatch_cmd+0x101/0x280 [scsi_mod] > [] scsi_request_fn+0x411/0x4d0 [scsi_mod] > [] __blk_run_queue+0x27/0x30 > [] blk_execute_rq_nowait+0x82/0x110 > [] blk_execute_rq+0x62/0xf0 > [] scsi_execute+0xe8/0x190 [scsi_mod] > [] scsi_execute_req+0xa3/0x130 [scsi_mod] > [] scsi_probe_lun+0x17a/0x450 [scsi_mod] > [] scsi_probe_and_add_lun+0x156/0x480 [scsi_mod] > [] __scsi_scan_target+0xdf/0x1f0 [scsi_mod] > [] scsi_scan_host_selected+0x183/0x1c0 [scsi_mod] > [] scsi_scan+0xdb/0xe0 [scsi_mod] > [] store_scan+0x13/0x20 [scsi_mod] > [] sysfs_write_file+0xcb/0x160 > [] vfs_write+0xce/0x140 > [] sys_write+0x53/0xa0 > [] system_call_fastpath+0x16/0x1b > [<00007f611c9d9300>] 0x7f611c9d92ff > > --- > drivers/scsi/scsi_lib.c | 4 +++- > include/linux/blk_types.h | 4 +++- > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 17bb541..7129701 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1311,9 +1311,11 @@ scsi_prep_state_check(struct scsi_device *sdev, struct request *req) > "rejecting I/O to dead device\n"); > ret = BLKPREP_KILL; > break; > - case SDEV_QUIESCE: > case SDEV_BLOCK: > case SDEV_CREATED_BLOCK: > + ret = BLKPREP_DEFER; > + break; > + case SDEV_QUIESCE: > /* > * If the devices is blocked we defer normal commands. > */ > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h > index c294e3e..a1b25e3 100644 > --- a/include/linux/blk_types.h > +++ b/include/linux/blk_types.h > @@ -181,7 +181,9 @@ enum rq_flag_bits { > __REQ_ELVPRIV, /* elevator private data attached */ > __REQ_FAILED, /* set if the request failed */ > __REQ_QUIET, /* don't worry about errors */ > - __REQ_PREEMPT, /* set for "ide_preempt" requests */ > + __REQ_PREEMPT, /* set for "ide_preempt" requests and also > + for requests for which the SCSI "quiesce" > + state must be ignored. */ > __REQ_ALLOCED, /* request came from our alloc pool */ > __REQ_COPY_USER, /* contains copies of user pages */ > __REQ_FLUSH_SEQ, /* request for flush sequence */ > Yeah. Did some basic tests and it works for me with iscsi and fc. Will try to do some real testing over the weekend. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html