[PATCH] scsi:Prevent deletion of SCSI block device in use

[Vasundhara Gurunath <vasundhara.gurunath@hpe.com>]

SCSI block device can be removed, using write to sysfs delete file as below:
echo 1 > /sys/block/sdX/device/delete
If the device is in use by applications, or part of system configuration
such as boot device, removal can result in application disruptions or
system down time.

An additional write option ? is added to SCSI sysfs interface as below,
in order to prevent accidental deletion of devices in use.
echo ? > /sys/block/sdX/device/delete

In the absence of any usage, this option proceeds with device deletion.
If the device is open, deletion is prevented, and active Open and IO
counts at the time of deletion is logged. Information logged during latest
delete attempt can be obtained by issuing a read to the delete file as below:
cat  /sys/block/sdX/device/delete

Signed-off-by: Vasundhara Gurunath <vasundhara.gurunath@hpe.com>
---
 drivers/scsi/scsi_sysfs.c  | 51 +++++++++++++++++++++++++++++++++++++++++++++-
 drivers/scsi/sd.c          |  5 ++++-
 include/scsi/scsi_device.h |  2 ++
 3 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 0734927..716b22a 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -12,6 +12,9 @@
 #include <linux/blkdev.h>
 #include <linux/device.h>
 #include <linux/pm_runtime.h>
+#include <linux/time.h>
+#include <linux/timer.h>
+
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_device.h>
@@ -457,6 +460,9 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 	kfree(sdev->vpd_pg83);
 	kfree(sdev->vpd_pg80);
 	kfree(sdev->inquiry);
+	if (sdev->delete_msg_buf != NULL)
+		kfree(sdev->delete_msg_buf);
+
 	kfree(sdev);
 
 	if (parent)
@@ -709,11 +715,54 @@ static ssize_t
 sdev_store_delete(struct device *dev, struct device_attribute *attr,
 		  const char *buf, size_t count)
 {
+	struct scsi_device *sdev = to_scsi_device(dev);
+	struct timeval tv;
+	struct tm tms;
+
+	if (buf[0] == '?')  {
+		if (sdev->usage_count) {
+			/*
+			 * Buffer to hold I/O statistics on delete attempt.
+			 */
+			if (sdev->delete_msg_buf == NULL) {
+				sdev->delete_msg_buf =
+				kmalloc(128, GFP_KERNEL);
+				memset(sdev->delete_msg_buf, 0, 128);
+			}
+			do_gettimeofday(&tv);
+			time_to_tm(tv.tv_sec, 0, &tms);
+			sprintf(sdev->delete_msg_buf,
+				"Last delete attempt: %d:%d:%d %02d:%02d\n"
+				"Open Count : %d\n"
+				"IO Active Count : %d\n"
+				"IO Done Count : %d\n",
+				tms.tm_mday, tms.tm_mon + 1,
+				tms.tm_year + 1900,
+				tms.tm_hour, tms.tm_min,
+				sdev->usage_count,
+				sdev->iorequest_cnt.counter,
+				sdev->iodone_cnt.counter);
+
+				return count;
+			}
+		}
+
 	if (device_remove_file_self(dev, attr))
 		scsi_remove_device(to_scsi_device(dev));
 	return count;
 };
-static DEVICE_ATTR(delete, S_IWUSR, NULL, sdev_store_delete);
+
+static ssize_t sdev_show_delete(struct device *dev,
+		struct device_attribute *attr, char *buf) {
+
+	struct scsi_device *sdev = to_scsi_device(dev);
+	if (sdev->delete_msg_buf != NULL)
+		return sprintf(buf, "%s", sdev->delete_msg_buf);
+	else
+		return 0;
+}
+static DEVICE_ATTR(delete, S_IRUGO | S_IWUSR, sdev_show_delete,
+			 sdev_store_delete);
 
 static ssize_t
 store_state_field(struct device *dev, struct device_attribute *attr,
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d3e852a..d5cf25c 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1235,6 +1235,7 @@ static int sd_open(struct block_device *bdev, fmode_t mode)
 		if (scsi_block_when_processing_errors(sdev))
 			scsi_set_medium_removal(sdev, SCSI_REMOVAL_PREVENT);
 	}
+	sdev->usage_count = sdkp->openers.counter;
 
 	return 0;
 
@@ -1267,7 +1268,7 @@ static void sd_release(struct gendisk *disk, fmode_t mode)
 		if (scsi_block_when_processing_errors(sdev))
 			scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);
 	}
-
+	sdev->usage_count = sdkp->openers.counter;
 	/*
 	 * XXX and what if there are packets in flight and this close()
 	 * XXX is followed by a "rmmod sd_mod"?
@@ -3082,6 +3083,8 @@ static int sd_probe(struct device *dev)
 	atomic_set(&sdkp->openers, 0);
 	atomic_set(&sdkp->device->ioerr_cnt, 0);
 
+	sdp->usage_count = sdkp->openers.counter;
+
 	if (!sdp->request_queue->rq_timeout) {
 		if (sdp->type != TYPE_MOD)
 			blk_queue_rq_timeout(sdp->request_queue, SD_TIMEOUT);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 8a95631..ab79675 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -208,6 +208,8 @@ struct scsi_device {
 
 	unsigned char		access_state;
 	enum scsi_device_state sdev_state;
+	char                    *delete_msg_buf;
+	int                     usage_count;
 	unsigned long		sdev_data[0];
 } __attribute__((aligned(sizeof(unsigned long))));
 
-- 
1.8.3.1