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Commit 409f3499 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Jens Axboe
Browse files

scsi/sd: remove big kernel lock 



Every user of the BKL in the sd driver is the
result of the pushdown from the block layer
into the open/close/ioctl functions.

The only place that used to rely on the BKL is
the sdkp->openers variable, which gets converted
into an atomic_t.

Nothing else seems to rely on the BKL, since the
functions do not touch global data without holding
another lock, and the open/close functions are
still protected from concurrent execution using
the bdev->bd_mutex.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Cc: linux-scsi@vger.kernel.org
Cc: "James E.J. Bottomley" <James.Bottomley@suse.de>
Acked-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 15392efb

drivers/scsi/sd.c

+7 −10
Original line number Diff line number Diff line
@@ -783,6 +783,8 @@ static int sd_prep_fn(struct request_queue *q, struct request *rq) 
 *	or from within the kernel (e.g. as a result of a mount(1) ).

 *	In the latter case @inode and @filp carry an abridged amount

 *	of information as noted above.

 *

 *	Locking: called with bdev->bd_mutex held.

 **/

static int sd_open(struct block_device *bdev, fmode_t mode)

{
@@ -795,7 +797,6 @@ static int sd_open(struct block_device *bdev, fmode_t mode) 


	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_open\n"));



	lock_kernel();

	sdev = sdkp->device;



	/*
@@ -834,17 +835,15 @@ static int sd_open(struct block_device *bdev, fmode_t mode) 
	if (!scsi_device_online(sdev))

		goto error_out;



	if (!sdkp->openers++ && sdev->removable) {

	if ((atomic_inc_return(&sdkp->openers) == 1) && sdev->removable) {

		if (scsi_block_when_processing_errors(sdev))

			scsi_set_medium_removal(sdev, SCSI_REMOVAL_PREVENT);

	}



	unlock_kernel();

	return 0;



error_out:

	scsi_disk_put(sdkp);

	unlock_kernel();

	return retval;	

}
@@ -858,6 +857,8 @@ error_out: 
 *

 *	Note: may block (uninterruptible) if error recovery is underway

 *	on this disk.

 *

 *	Locking: called with bdev->bd_mutex held.

 **/

static int sd_release(struct gendisk *disk, fmode_t mode)

{
@@ -866,8 +867,7 @@ static int sd_release(struct gendisk *disk, fmode_t mode) 


	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_release\n"));



	lock_kernel();

	if (!--sdkp->openers && sdev->removable) {

	if (atomic_dec_return(&sdkp->openers) && sdev->removable) {

		if (scsi_block_when_processing_errors(sdev))

			scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);

	}
@@ -877,7 +877,6 @@ static int sd_release(struct gendisk *disk, fmode_t mode) 
	 * XXX is followed by a "rmmod sd_mod"?

	 */

	scsi_disk_put(sdkp);

	unlock_kernel();

	return 0;

}
@@ -930,7 +929,6 @@ static int sd_ioctl(struct block_device *bdev, fmode_t mode, 
	SCSI_LOG_IOCTL(1, printk("sd_ioctl: disk=%s, cmd=0x%x\n",

						disk->disk_name, cmd));



	lock_kernel();

	/*

	 * If we are in the middle of error recovery, don't let anyone

	 * else try and use this device.  Also, if error recovery fails, it
@@ -960,7 +958,6 @@ static int sd_ioctl(struct block_device *bdev, fmode_t mode, 
			break;

	}

out:

	unlock_kernel();

	return error;

}
@@ -2346,7 +2343,7 @@ static int sd_probe(struct device *dev) 
	sdkp->driver = &sd_template;

	sdkp->disk = gd;

	sdkp->index = index;

	sdkp->openers = 0;

	atomic_set(&sdkp->openers, 0);

	sdkp->previous_state = 1;



	if (!sdp->request_queue->rq_timeout) {

drivers/scsi/sd.h

+1 −1
Original line number Diff line number Diff line
@@ -47,7 +47,7 @@ struct scsi_disk { 
	struct scsi_device *device;

	struct device	dev;

	struct gendisk	*disk;

	unsigned int	openers;	/* protected by BKL for now, yuck */

	atomic_t	openers;

	sector_t	capacity;	/* size in 512-byte sectors */

	u32		index;

	unsigned short	hw_sector_size;