Commit 57f7225a authored by John Garry's avatar John Garry Committed by Martin K. Petersen
Browse files

scsi: scsi_debug: Only allow sdebug_max_queue be modified when no shosts 



The shost->can_queue value is initially used to set per-HW queue context
tag depth in the block layer. This ensures that the shost is not sent too
many commands which it can deal with. However lowering sdebug_max_queue
separately means that we can easily overload the shost, as in the following
example:

$ cat /sys/bus/pseudo/drivers/scsi_debug/max_queue
192
$ cat /sys/class/scsi_host/host0/can_queue
192
$ echo 100 > /sys/bus/pseudo/drivers/scsi_debug/max_queue
$ cat /sys/class/scsi_host/host0/can_queue
192
$ fio --filename=/dev/sda --direct=1 --rw=read --bs=4k --iodepth=256
--runtime=1200 --numjobs=10 --time_based --group_reporting
--name=iops-test-job --eta-newline=1 --readonly    --ioengine=io_uring
--hipri --exitall_on_error
iops-test-job: (g=0): rw=read, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=256
...
fio-3.28
Starting 10 processes
[  111.269885] scsi_io_completion_action: 400 callbacks suppressed
[  111.269885] blk_print_req_error: 400 callbacks suppressed
[  111.269889] I/O error, dev sda, sector 440 op 0x0:(READ) flags 0x1200000 phys_seg 1 prio class 2
[  111.269892] sd 0:0:0:0: [sda] tag#132 FAILED Result: hostbyte=DID_ABORT driverbyte=DRIVER_OK cmd_age=0s
[  111.269897] sd 0:0:0:0: [sda] tag#132 CDB: Read(10) 28 00 00 00 01 68 00 00 08 00
[  111.277058] I/O error, dev sda, sector 360 op 0x0:(READ) flags 0x1200000 phys_seg 1 prio class 2

[...]

Ensure that this cannot happen by allowing sdebug_max_queue be modified
only when we have no shosts. As such, any shost->can_queue value will match
sdebug_max_queue, and sdebug_max_queue cannot be modified separately.

Since retired_max_queue is no longer set, remove support.

Continue to apply the restriction that sdebug_host_max_queue cannot be
modified when sdebug_host_max_queue is set. Adding support for that would
mean extra code, and no one has complained about this restriction
previously.

A command like the following may be used to remove a shost:
echo -1 > /sys/bus/pseudo/drivers/scsi_debug/add_host

Signed-off-by: default avatarJohn Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230327074310.1862889-11-john.g.garry@oracle.com


Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 12f3eef0

drivers/scsi/scsi_debug.c

+6 −61
Original line number Diff line number Diff line
@@ -762,7 +762,6 @@ static int sdebug_max_luns = DEF_MAX_LUNS; 
static int sdebug_max_queue = SDEBUG_CANQUEUE;	/* per submit queue */

static unsigned int sdebug_medium_error_start = OPT_MEDIUM_ERR_ADDR;

static int sdebug_medium_error_count = OPT_MEDIUM_ERR_NUM;

static atomic_t retired_max_queue;	/* if > 0 then was prior max_queue */

static int sdebug_ndelay = DEF_NDELAY;	/* if > 0 then unit is nanoseconds */

static int sdebug_no_lun_0 = DEF_NO_LUN_0;

static int sdebug_no_uld;
@@ -4928,7 +4927,6 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp) 
{

	struct sdebug_queued_cmd *sqcp = container_of(sd_dp, struct sdebug_queued_cmd, sd_dp);

	int qc_idx;

	int retiring = 0;

	unsigned long flags, iflags;

	struct scsi_cmnd *scp = sqcp->scmd;

	struct sdebug_scsi_cmd *sdsc;
@@ -4959,9 +4957,6 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp) 
		sd_dp->aborted = false;

	ASSIGN_QUEUED_CMD(scp, NULL);



	if (unlikely(atomic_read(&retired_max_queue) > 0))

		retiring = 1;



	sqp->qc_arr[qc_idx] = NULL;

	if (unlikely(!test_and_clear_bit(qc_idx, sqp->in_use_bm))) {

		spin_unlock_irqrestore(&sdsc->lock, flags);
@@ -4970,23 +4965,6 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp) 
		goto out;

	}



	if (unlikely(retiring)) {	/* user has reduced max_queue */

		int k, retval;



		retval = atomic_read(&retired_max_queue);

		if (qc_idx >= retval) {

			spin_unlock_irqrestore(&sdsc->lock, flags);

			spin_unlock_irqrestore(&sqp->qc_lock, iflags);

			pr_err("index %d too large\n", retval);

			goto out;

		}

		k = find_last_bit(sqp->in_use_bm, retval);

		if ((k < sdebug_max_queue) || (k == retval))

			atomic_set(&retired_max_queue, 0);

		else

			atomic_set(&retired_max_queue, k + 1);

	}



	spin_unlock_irqrestore(&sdsc->lock, flags);

	spin_unlock_irqrestore(&sqp->qc_lock, iflags);
@@ -6431,29 +6409,18 @@ static ssize_t max_queue_show(struct device_driver *ddp, char *buf) 
static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,

			       size_t count)

{

	int j, n, k, a;

	struct sdebug_queue *sqp;

	int n;



	if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n > 0) &&

	    (n <= SDEBUG_CANQUEUE) &&

	    (sdebug_host_max_queue == 0)) {

		mutex_lock(&sdebug_host_list_mutex);

		block_unblock_all_queues(true);

		k = 0;

		for (j = 0, sqp = sdebug_q_arr; j < submit_queues;

		     ++j, ++sqp) {

			a = find_last_bit(sqp->in_use_bm, SDEBUG_CANQUEUE);

			if (a > k)

				k = a;

		}



		/* We may only change sdebug_max_queue when we have no shosts */

		if (list_empty(&sdebug_host_list))

			sdebug_max_queue = n;

		if (k == SDEBUG_CANQUEUE)

			atomic_set(&retired_max_queue, 0);

		else if (k >= n)

			atomic_set(&retired_max_queue, k + 1);

		else

			atomic_set(&retired_max_queue, 0);

		block_unblock_all_queues(false);

			count = -EBUSY;

		mutex_unlock(&sdebug_host_list_mutex);

		return count;

	}
@@ -6882,7 +6849,6 @@ static int __init scsi_debug_init(void) 


	ramdisk_lck_a[0] = &atomic_rw;

	ramdisk_lck_a[1] = &atomic_rw2;

	atomic_set(&retired_max_queue, 0);



	if (sdebug_ndelay >= 1000 * 1000 * 1000) {

		pr_warn("ndelay must be less than 1 second, ignored\n");
@@ -7520,7 +7486,6 @@ static bool sdebug_blk_mq_poll_iter(struct request *rq, void *opaque) 
	struct sdebug_queue *sqp;

	unsigned long flags;

	int queue_num = data->queue_num;

	bool retiring = false;

	int qc_idx;

	ktime_t time;
@@ -7554,9 +7519,6 @@ static bool sdebug_blk_mq_poll_iter(struct request *rq, void *opaque) 
		return true;

	}



	if (unlikely(atomic_read(&retired_max_queue) > 0))

		retiring = true;



	qc_idx = sd_dp->sqa_idx;

	sqp->qc_arr[qc_idx] = NULL;

	if (unlikely(!test_and_clear_bit(qc_idx, sqp->in_use_bm))) {
@@ -7567,23 +7529,6 @@ static bool sdebug_blk_mq_poll_iter(struct request *rq, void *opaque) 
		return true;

	}



	if (unlikely(retiring)) {	/* user has reduced max_queue */

		int k, retval = atomic_read(&retired_max_queue);



		if (qc_idx >= retval) {

			pr_err("index %d too large\n", retval);

			spin_unlock_irqrestore(&sdsc->lock, flags);

			sdebug_free_queued_cmd(sqcp);

			return true;

		}



		k = find_last_bit(sqp->in_use_bm, retval);

		if ((k < sdebug_max_queue) || (k == retval))

			atomic_set(&retired_max_queue, 0);

		else

			atomic_set(&retired_max_queue, k + 1);

	}



	ASSIGN_QUEUED_CMD(cmd, NULL);

	spin_unlock_irqrestore(&sdsc->lock, flags);