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Commit cb2fb68d authored by Vaughan Cao's avatar Vaughan Cao Committed by Christoph Hellwig
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sd: notify block layer when using temporary change to cache_type 



This is a fix for commit 39c60a09

  "sd: fix array cache flushing bug causing performance problems"

We must notify the block layer via q->flush_flags after a temporary change
of the cache_type to write through.  Without this, a SYNCHRONIZE CACHE
command will still be generated.  This patch factors out a helper that
can be called from sd_revalidate_disk and cache_type_store.

Signed-off-by: default avatarVaughan Cao <vaughan.cao@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 6bb5e6e7

drivers/scsi/sd.c

+15 −8
Original line number Diff line number Diff line
@@ -134,6 +134,19 @@ static const char *sd_cache_types[] = { 
	"write back, no read (daft)"

};



static void sd_set_flush_flag(struct scsi_disk *sdkp)

{

	unsigned flush = 0;



	if (sdkp->WCE) {

		flush |= REQ_FLUSH;

		if (sdkp->DPOFUA)

			flush |= REQ_FUA;

	}



	blk_queue_flush(sdkp->disk->queue, flush);

}



static ssize_t

cache_type_store(struct device *dev, struct device_attribute *attr,

		 const char *buf, size_t count)
@@ -177,6 +190,7 @@ cache_type_store(struct device *dev, struct device_attribute *attr, 
	if (sdkp->cache_override) {

		sdkp->WCE = wce;

		sdkp->RCD = rcd;

		sd_set_flush_flag(sdkp);

		return count;

	}
@@ -2698,7 +2712,6 @@ static int sd_revalidate_disk(struct gendisk *disk) 
	struct scsi_disk *sdkp = scsi_disk(disk);

	struct scsi_device *sdp = sdkp->device;

	unsigned char *buffer;

	unsigned flush = 0;



	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,

				      "sd_revalidate_disk\n"));
@@ -2744,13 +2757,7 @@ static int sd_revalidate_disk(struct gendisk *disk) 
	 * We now have all cache related info, determine how we deal

	 * with flush requests.

	 */

	if (sdkp->WCE) {

		flush |= REQ_FLUSH;

		if (sdkp->DPOFUA)

			flush |= REQ_FUA;

	}



	blk_queue_flush(sdkp->disk->queue, flush);

	sd_set_flush_flag(sdkp);



	set_capacity(disk, sdkp->capacity);

	sd_config_write_same(sdkp);