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author | Jan Höppner <hoeppner@linux.vnet.ibm.com> | 2016-10-13 13:31:39 +0200 |
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committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-10-28 10:09:04 +0200 |
commit | 9f9d53e5bdb4362a73b801176cae49e77bea41fb (patch) | |
tree | 6905495f3538632f731934c83f920eae671892ac /drivers/s390/block/dasd_devmap.c | |
parent | 9de67725c80cb8a7b34b1932e196d2ed61a08879 (diff) | |
download | linux-stable-9f9d53e5bdb4362a73b801176cae49e77bea41fb.tar.gz linux-stable-9f9d53e5bdb4362a73b801176cae49e77bea41fb.tar.bz2 linux-stable-9f9d53e5bdb4362a73b801176cae49e77bea41fb.zip |
s390/dasd: Fix locking issue when changing RO attribute
The function dasd_ro_store() calls set_disk_ro() to set the device in
question read-only. Since set_disk_ro() might sleep, we can't call it
while holding a lock. However, we also can't simply check if the device,
block, and gdp references are valid before we call set_disk_ro() because
an offline processing might have been started in the meanwhile which
will destroy those references.
In order to reliably call set_disk_ro() we have to ensure several
things:
- Still check validity of the mentioned references but additionally
check if offline processing is running and bail out accordingly. Also,
do this while holding the device lock.
- To ensure that the block device is still safe after the lock, increase
the open_count while still holding the device lock.
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>
Diffstat (limited to 'drivers/s390/block/dasd_devmap.c')
-rw-r--r-- | drivers/s390/block/dasd_devmap.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c index c1979ecce821..cbae6ab448b8 100644 --- a/drivers/s390/block/dasd_devmap.c +++ b/drivers/s390/block/dasd_devmap.c @@ -761,6 +761,7 @@ dasd_ro_store(struct device *dev, struct device_attribute *attr, { struct ccw_device *cdev = to_ccwdev(dev); struct dasd_device *device; + unsigned long flags; unsigned int val; int rc; @@ -775,10 +776,22 @@ dasd_ro_store(struct device *dev, struct device_attribute *attr, if (IS_ERR(device)) return PTR_ERR(device); + spin_lock_irqsave(get_ccwdev_lock(cdev), flags); val = val || test_bit(DASD_FLAG_DEVICE_RO, &device->flags); - if (device->block && device->block->gdp) - set_disk_ro(device->block->gdp, val); + if (!device->block || !device->block->gdp || + test_bit(DASD_FLAG_OFFLINE, &device->flags)) { + spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags); + goto out; + } + /* Increase open_count to avoid losing the block device */ + atomic_inc(&device->block->open_count); + spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags); + + set_disk_ro(device->block->gdp, val); + atomic_dec(&device->block->open_count); + +out: dasd_put_device(device); return count; |