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>

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index c82df8bd4d8931cc72d3654a74edde4e4c9dd75b..27f5bfd1def343e205c2710a587571650026410f 100644 (file)
--- 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)