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>

1 files changed, 5 insertions, 15 deletions

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index c82df8bd4d89..27f5bfd1def3 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -673,24 +673,20 @@ fail:
 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 @@ static void get_sectorsize(struct scsi_cd *cd)
 
         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)