scsi: scsi_debug: Allocate the MODE SENSE response from the heap

Make the MODE SENSE response buffer larger and allocate it from the heap.
This patch prepares for adding support for the IO Advice Hints Grouping
mode page.

Suggested-by: Douglas Gilbert <dgilbert@interlog.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240130214911.1863909-17-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: bvanassche

drivers/scsi/scsi_debug.c

@@ -43,6 +43,7 @@
 #include <linux/prefetch.h>
 #include <linux/debugfs.h>
 #include <linux/async.h>
+#include <linux/cleanup.h>
 
 #include <net/checksum.h>
 
@@ -2631,7 +2632,8 @@ static int resp_sas_sha_m_spg(unsigned char *p, int pcontrol)
 	return sizeof(sas_sha_m_pg);
 }
 
-#define SDEBUG_MAX_MSENSE_SZ 256
+/* PAGE_SIZE is more than necessary but provides room for future expansion. */
+#define SDEBUG_MAX_MSENSE_SZ PAGE_SIZE
 
 static int resp_mode_sense(struct scsi_cmnd *scp,
 			   struct sdebug_dev_info *devip)
@@ -2642,10 +2644,13 @@ static int resp_mode_sense(struct scsi_cmnd *scp,
 	int target_dev_id;
 	int target = scp->device->id;
 	unsigned char *ap;
-	unsigned char arr[SDEBUG_MAX_MSENSE_SZ];
+	unsigned char *arr __free(kfree);
 	unsigned char *cmd = scp->cmnd;
 	bool dbd, llbaa, msense_6, is_disk, is_zbc;
 
+	arr = kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC);
+	if (!arr)
+		return -ENOMEM;
 	dbd = !!(cmd[1] & 0x8);		/* disable block descriptors */
 	pcontrol = (cmd[2] & 0xc0) >> 6;
 	pcode = cmd[2] & 0x3f;