Stop SSD from waiting for "Spinning up disk..."

From: Jeff Chua <jeff.chua.linux@gmail.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Stop SSD from waiting for "Spinning up disk..."
Date: Mon, 22 Jun 2015 15:25:29 +0800 (SGT)	[thread overview]
Message-ID: <Pine.LNX.4.64.1506221521480.7601@boston.corp.fedex.com> (raw)


There's no need to wait for disk spin-up for USB SSD devices. This 
patch allow the SSD to skip waiting disk spin-up by passing sd_mod.ssd=1 
during boot-up.

If there's a better way to handle this, please share.


Thanks,
Jeff

--- linux/drivers/scsi/sd.c	2015-05-25 07:29:44.000000000 +0800
+++ linux/drivers/scsi/sd.c	2015-06-19 22:17:35.000000000 +0800
@@ -92,6 +92,9 @@
     MODULE_ALIAS_SCSI_DEVICE(TYPE_MOD);
     MODULE_ALIAS_SCSI_DEVICE(TYPE_RBC);

+static int ssd = 0;
+module_param(ssd, int, 0);
+
     #if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
     #define SD_MINORS	16
     #else
@@ -2738,7 +2741,9 @@
     		goto out;
     	}

-	sd_spinup_disk(sdkp);
+	sd_printk(KERN_NOTICE, sdkp, "ssd %s\n", ssd == 0 ? "off" : "on");
+	if(!ssd)
+		sd_spinup_disk(sdkp);

     	/*
     	 * Without media there is no reason to ask; moreover, some devices
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