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Defer processing of REQ_PREEMPT requests for blocked devices

PATCH RESEND In review Bart Van Assche 2 participants 2 messages Mar 4, 2015 – Apr 6, 2015

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SCSI Block layer
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Bart Van Assche

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#0 lore raw

PATCH RESEND 1/1 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
Reported-by Max Gurtuvoy <[email protected]>
Signed-off-by Bart Van Assche <[email protected]>
Cc Mike Christie <[email protected]>
Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <[email protected]>
Cc <[email protected]>
---
 drivers/scsi/scsi_lib.c   | 4 +++-
 include/linux/blk_types.h | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)
drivers/scsi/scsi_lib.c +3 -1
index 54d7a6c..b1a2631 100644
@@ -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.
 			 */
include/linux/blk_types.h +3 -1
index c294e3e..a1b25e3 100644
@@ -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 */
Signature · 1 line
2.1.4
Reviewed-by on v1 1/1
#1 lore raw
Quoted 65 lines · Bart Van Assche

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 <[email protected]>
Signed-off-by Bart Van Assche <[email protected]>
Cc Mike Christie <[email protected]>
Cc Christoph Hellwig <[email protected]>
Cc Sagi Grimberg <[email protected]>
Cc <[email protected]>
---
 drivers/scsi/scsi_lib.c   | 4 +++-
 include/linux/blk_types.h | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)
drivers/scsi/scsi_lib.c +3 -1
index 54d7a6c..b1a2631 100644
@@ -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.
 			 */
include/linux/blk_types.h +0 -0
index c294e3e..a1b25e3 100644

include/linux/blk_types.h enum rq_flag_bits { · line 189

Quoted 10 lines
include/linux/blk_types.h +3 -1
@@ -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 */

Look ok to me. Also tested here with iscsi and FC.

Reviewed-by Mike Christie <[email protected]>