scsi: sr avoids useless buffer allocation

blk_rq_map_kern can handle the stack buffers correctly (avoid DMA from/to the stack buffers by using the bounce buffer) so we don't need to complicate the code by allocating just 8 bytes. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Tejun Heo <htejun@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

scsi: sr avoids useless buffer allocation
blk_rq_map_kern can handle the stack buffers correctly (avoid DMA from/to the stack buffers by using the bounce buffer) so we don't need to complicate the code by allocating just 8 bytes. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Tejun Heo <htejun@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
FUJITA Tomonori · Jens Axboe
1 parent 30c00eda73
Showing 1 changed file with 5 additions and 15 deletions Side-by-side Diff
drivers/scsi/sr.c
@@ -673,24 +673,20 @@
 static void get_sectorsize(struct scsi_cd *cd)
 {
 	unsigned char cmd[10];
-	unsigned char *buffer;
+	unsigned char buffer[8];
 	int the_result, retries = 3;
 	int sector_size;
 	struct request_queue *queue;
  
-	buffer = kmalloc(512, GFP_KERNEL | GFP_DMA);
-	if (!buffer)
-		goto Enomem;
-
 	do {
 		cmd[0] = READ_CAPACITY;
 		memset((void *) &cmd[1], 0, 9);
-		memset(buffer, 0, 8);
+		memset(buffer, 0, sizeof(buffer));
  
 		/* Do the command and wait.. */
 		the_result = scsi_execute_req(cd->device, cmd, DMA_FROM_DEVICE,
-					      buffer, 8, NULL, SR_TIMEOUT,
-					      MAX_RETRIES);
+					      buffer, sizeof(buffer), NULL,
+					      SR_TIMEOUT, MAX_RETRIES);
  
 		retries--;
  
  
@@ -745,14 +741,8 @@
  
 	queue = cd->device->request_queue;
 	blk_queue_hardsect_size(queue, sector_size);
-out:
-	kfree(buffer);
-	return;
  
-Enomem:
-	cd->capacity = 0x1fffff;
-	cd->device->sector_size = 2048;	/* A guess, just in case */
-	goto out;
+	return;
 }
  
 static void get_capabilities(struct scsi_cd *cd)
...	...	@@ -673,24 +673,20 @@
673	673	static void get_sectorsize(struct scsi_cd *cd)
674	674	{
675	675	unsigned char cmd[10];
676		- unsigned char *buffer;
	676	+ unsigned char buffer[8];
677	677	int the_result, retries = 3;
678	678	int sector_size;
679	679	struct request_queue *queue;
680	680
681		- buffer = kmalloc(512, GFP_KERNEL \| GFP_DMA);
682		- if (!buffer)
683		- goto Enomem;
684		-
685	681	do {
686	682	cmd[0] = READ_CAPACITY;
687	683	memset((void *) &cmd[1], 0, 9);
688		- memset(buffer, 0, 8);
	684	+ memset(buffer, 0, sizeof(buffer));
689	685
690	686	/* Do the command and wait.. */
691	687	the_result = scsi_execute_req(cd->device, cmd, DMA_FROM_DEVICE,
692		- buffer, 8, NULL, SR_TIMEOUT,
693		- MAX_RETRIES);
	688	+ buffer, sizeof(buffer), NULL,
	689	+ SR_TIMEOUT, MAX_RETRIES);
694	690
695	691	retries--;
696	692
697	693
...	...	@@ -745,14 +741,8 @@
745	741
746	742	queue = cd->device->request_queue;
747	743	blk_queue_hardsect_size(queue, sector_size);
748		-out:
749		- kfree(buffer);
750		- return;
751	744
752		-Enomem:
753		- cd->capacity = 0x1fffff;
754		- cd->device->sector_size = 2048; /* A guess, just in case */
755		- goto out;
	745	+ return;
756	746	}
757	747
758	748	static void get_capabilities(struct scsi_cd *cd)