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: [<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
---
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 */
--
2.1.4
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