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s390/dasd: Fix locking issue when changing EER attribute 

The reference to a device in question may get lost when the extended
error reporting (EER) attribute is being enabled/disabled while the
device is set offline at the same time. This is due to missing
refcounting and incorrect locking. Fix this by the following:

- In dasd_eer_store() get the device directly and handle the refcount
  accordingly.
- Move the lock in dasd_eer_enable() up so we can ensure safe
  processing.
- Check if the device is being set offline and return with -EBUSY if so.
- While at it, change the return code from -EPERM to -EMEDIUMTYPE as
  suggested by a FIXME, since that is what we're actually checking.

Reviewed-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Jan Höppner 2016-10-12 12:51:04 +02:00 committed by Martin Schwidefsky
parent 0f57c97f24
commit 9de67725c8
2 changed files with 34 additions and 22 deletions
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27
drivers/s390/block/dasd_devmap.c
View File

@ -1167,26 +1167,25 @@ static ssize_t
dasd_eer_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct dasd_devmap *devmap;
struct dasd_device *device;
unsigned int val;
int rc;
int rc = 0;
devmap = dasd_devmap_from_cdev(to_ccwdev(dev));
if (IS_ERR(devmap))
return PTR_ERR(devmap);
if (!devmap->device)
return -ENODEV;
device = dasd_device_from_cdev(to_ccwdev(dev));
if (IS_ERR(device))
return PTR_ERR(device);
if (kstrtouint(buf, 0, &val) || val > 1)
return -EINVAL;
if (val) {
rc = dasd_eer_enable(devmap->device);
if (rc)
return rc;
} else
dasd_eer_disable(devmap->device);
return count;
if (val)
rc = dasd_eer_enable(device);
else
dasd_eer_disable(device);
dasd_put_device(device);
return rc ? : count;
}
static DEVICE_ATTR(eer_enabled, 0644, dasd_eer_show, dasd_eer_store);

29
drivers/s390/block/dasd_eer.c
View File

@ -454,20 +454,30 @@ static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
*/
int dasd_eer_enable(struct dasd_device *device)
{
struct dasd_ccw_req *cqr;
struct dasd_ccw_req *cqr = NULL;
unsigned long flags;
struct ccw1 *ccw;
int rc = 0;
spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
if (device->eer_cqr)
return 0;
goto out;
else if (!device->discipline ||
strcmp(device->discipline->name, "ECKD"))
rc = -EMEDIUMTYPE;
else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
rc = -EBUSY;
if (!device->discipline || strcmp(device->discipline->name, "ECKD"))
return -EPERM; /* FIXME: -EMEDIUMTYPE ? */
if (rc)
goto out;
cqr = dasd_kmalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
SNSS_DATA_SIZE, device);
if (IS_ERR(cqr))
return -ENOMEM;
if (IS_ERR(cqr)) {
rc = -ENOMEM;
cqr = NULL;
goto out;
}
cqr->startdev = device;
cqr->retries = 255;
@ -485,15 +495,18 @@ int dasd_eer_enable(struct dasd_device *device)
cqr->status = DASD_CQR_FILLED;
cqr->callback = dasd_eer_snss_cb;
spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
if (!device->eer_cqr) {
device->eer_cqr = cqr;
cqr = NULL;
}
out:
spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
if (cqr)
dasd_kfree_request(cqr, device);
return 0;
return rc;
}
/*