From 409f3499a2cfcd1e9c2857c53af7fcce069f027f Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 7 Jul 2010 16:51:29 +0200 Subject: [PATCH] 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: Arnd Bergmann Cc: linux-scsi@vger.kernel.org Cc: "James E.J. Bottomley" Acked-by: Christoph Hellwig Signed-off-by: Jens Axboe --- drivers/scsi/sd.c | 17 +++++++---------- drivers/scsi/sd.h | 2 +- 2 files changed, 8 insertions(+), 11 deletions(-) diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 01680c7..fc5d69a 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -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) { diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h index 43d3caf..f81a930 100644 --- a/drivers/scsi/sd.h +++ b/drivers/scsi/sd.h @@ -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; -- 2.7.4