Defer processing of REQ_PREEMPT requests for blocked devices

commit bba0bdd7ad4713d82338bcd9b72d57e9335a664b upstream.

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: [<ffffffffa04e08f2>] mlx4_ib_post_send+0xd2/0xb30 [mlx4_ib]
Process rescan-scsi-bus (pid: 9241, threadinfo ffff88053484a000, task ffff880534aae100)
Call Trace:
 [<ffffffffa0718135>] srp_post_send+0x65/0x70 [ib_srp]
 [<ffffffffa071b9df>] srp_queuecommand+0x1cf/0x3e0 [ib_srp]
 [<ffffffffa0001ff1>] scsi_dispatch_cmd+0x101/0x280 [scsi_mod]
 [<ffffffffa0009ad1>] scsi_request_fn+0x411/0x4d0 [scsi_mod]
 [<ffffffff81223b37>] __blk_run_queue+0x27/0x30
 [<ffffffff8122a8d2>] blk_execute_rq_nowait+0x82/0x110
 [<ffffffff8122a9c2>] blk_execute_rq+0x62/0xf0
 [<ffffffffa000b0e8>] scsi_execute+0xe8/0x190 [scsi_mod]
 [<ffffffffa000b2f3>] scsi_execute_req+0xa3/0x130 [scsi_mod]
 [<ffffffffa000c1aa>] scsi_probe_lun+0x17a/0x450 [scsi_mod]
 [<ffffffffa000ce86>] scsi_probe_and_add_lun+0x156/0x480 [scsi_mod]
 [<ffffffffa000dc2f>] __scsi_scan_target+0xdf/0x1f0 [scsi_mod]
 [<ffffffffa000dfa3>] scsi_scan_host_selected+0x183/0x1c0 [scsi_mod]
 [<ffffffffa000edfb>] scsi_scan+0xdb/0xe0 [scsi_mod]
 [<ffffffffa000ee13>] store_scan+0x13/0x20 [scsi_mod]
 [<ffffffff811c8d9b>] sysfs_write_file+0xcb/0x160
 [<ffffffff811589de>] vfs_write+0xce/0x140
 [<ffffffff81158b53>] sys_write+0x53/0xa0
 [<ffffffff81464592>] system_call_fastpath+0x16/0x1b
 [<00007f611c9d9300>] 0x7f611c9d92ff

Reported-by: Max Gurtuvoy <maxg@mellanox.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0bdc4a7..f6a464a 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1206,9 +1206,11 @@ int 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 4053cbd..ddce23d 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -144,7 +144,9 @@ 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 */