scsi: sr avoids useless buffer allocation (62858dac) · Commits · 戴 / test

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>

drivers/scsi/sr.c

+5 −15

Original line number	Diff line number	Diff line
		@@ -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)

Admin message