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authorChristoph Hellwig <hch@lst.de>2014-04-11 19:07:01 +0200
committerChristoph Hellwig <hch@lst.de>2014-07-25 07:43:45 -0400
commit71e75c97f97a9645d25fbf3d8e4165a558f18747 (patch)
treefb85185386af55199c46499dc3ce366d227870e1 /drivers/scsi/scsi_sysfs.c
parent74665016086615bbaa3fa6f83af410a0a4e029ee (diff)
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scsi: convert device_busy to atomic_t
Avoid taking the queue_lock to check the per-device queue limit. Instead we do an atomic_inc_return early on to grab our slot in the queue, and if necessary decrement it after finishing all checks. Unlike the host and target busy counters this doesn't allow us to avoid the queue_lock in the request_fn due to the way the interface works, but it'll allow us to prepare for using the blk-mq code, which doesn't use the queue_lock at all, and it at least avoids a queue_lock round trip in scsi_device_unbusy, which is still important given how busy the queue_lock is. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Webb Scales <webbnh@hp.com> Acked-by: Jens Axboe <axboe@kernel.dk> Tested-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Robert Elliott <elliott@hp.com>
Diffstat (limited to 'drivers/scsi/scsi_sysfs.c')
-rw-r--r--drivers/scsi/scsi_sysfs.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index de57b8bca7be..79df9847edef 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -585,13 +585,21 @@ static int scsi_sdev_check_buf_bit(const char *buf)
* Create the actual show/store functions and data structures.
*/
sdev_rd_attr (device_blocked, "%d\n");
-sdev_rd_attr (device_busy, "%d\n");
sdev_rd_attr (type, "%d\n");
sdev_rd_attr (scsi_level, "%d\n");
sdev_rd_attr (vendor, "%.8s\n");
sdev_rd_attr (model, "%.16s\n");
sdev_rd_attr (rev, "%.4s\n");
+static ssize_t
+sdev_show_device_busy(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct scsi_device *sdev = to_scsi_device(dev);
+ return snprintf(buf, 20, "%d\n", atomic_read(&sdev->device_busy));
+}
+static DEVICE_ATTR(device_busy, S_IRUGO, sdev_show_device_busy, NULL);
+
/*
* TODO: can we make these symlinks to the block layer ones?
*/