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zv_suspend_lock in zvol_open()/zvol_release() #6342

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Aug 9, 2017
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zv_suspend_lock in zvol_open()/zvol_release() #6342

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64 changes: 41 additions & 23 deletions module/zfs/zvol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1304,9 +1304,9 @@ zvol_open(struct block_device *bdev, fmode_t flag)
{
zvol_state_t *zv;
int error = 0;
boolean_t drop_suspend = B_FALSE;
boolean_t drop_suspend = B_TRUE;

ASSERT(!mutex_owned(&zvol_state_lock));
ASSERT(!MUTEX_HELD(&zvol_state_lock));

mutex_enter(&zvol_state_lock);
/*
Expand All @@ -1321,23 +1321,31 @@ zvol_open(struct block_device *bdev, fmode_t flag)
return (SET_ERROR(-ENXIO));
}

/* take zv_suspend_lock before zv_state_lock */
rw_enter(&zv->zv_suspend_lock, RW_READER);

mutex_enter(&zv->zv_state_lock);

/*
* make sure zvol is not suspended during first open
* (hold zv_suspend_lock), otherwise, drop the lock
* (hold zv_suspend_lock) and respect proper lock acquisition
* ordering - zv_suspend_lock before zv_state_lock
*/
if (zv->zv_open_count == 0) {
drop_suspend = B_TRUE;
if (!rw_tryenter(&zv->zv_suspend_lock, RW_READER)) {
mutex_exit(&zv->zv_state_lock);
rw_enter(&zv->zv_suspend_lock, RW_READER);
mutex_enter(&zv->zv_state_lock);
/* check to see if zv_suspend_lock is needed */
if (zv->zv_open_count != 0) {
rw_exit(&zv->zv_suspend_lock);
drop_suspend = B_FALSE;
}
}
} else {
rw_exit(&zv->zv_suspend_lock);
drop_suspend = B_FALSE;
}

mutex_exit(&zvol_state_lock);

ASSERT(MUTEX_HELD(&zv->zv_state_lock));
ASSERT(zv->zv_open_count != 0 || RW_READ_HELD(&zv->zv_suspend_lock));

if (zv->zv_open_count == 0) {
error = zvol_first_open(zv);
if (error)
Expand Down Expand Up @@ -1374,28 +1382,38 @@ static int
zvol_release(struct gendisk *disk, fmode_t mode)
{
zvol_state_t *zv;
boolean_t drop_suspend = B_FALSE;
boolean_t drop_suspend = B_TRUE;

ASSERT(!mutex_owned(&zvol_state_lock));
ASSERT(!MUTEX_HELD(&zvol_state_lock));

mutex_enter(&zvol_state_lock);
zv = disk->private_data;
ASSERT(zv && zv->zv_open_count > 0);

/* take zv_suspend_lock before zv_state_lock */
rw_enter(&zv->zv_suspend_lock, RW_READER);

mutex_enter(&zv->zv_state_lock);
mutex_exit(&zvol_state_lock);

ASSERT(zv->zv_open_count > 0);
/*
* make sure zvol is not suspended during last close
* (hold zv_suspend_lock), otherwise, drop the lock
* (hold zv_suspend_lock) and respect proper lock acquisition
* ordering - zv_suspend_lock before zv_state_lock
*/
if (zv->zv_open_count == 1)
drop_suspend = B_TRUE;
else
rw_exit(&zv->zv_suspend_lock);
if (zv->zv_open_count == 1) {
if (!rw_tryenter(&zv->zv_suspend_lock, RW_READER)) {
mutex_exit(&zv->zv_state_lock);
rw_enter(&zv->zv_suspend_lock, RW_READER);
mutex_enter(&zv->zv_state_lock);
/* check to see if zv_suspend_lock is needed */
if (zv->zv_open_count != 1) {
rw_exit(&zv->zv_suspend_lock);
drop_suspend = B_FALSE;
}
}
} else {
drop_suspend = B_FALSE;
}
mutex_exit(&zvol_state_lock);

ASSERT(MUTEX_HELD(&zv->zv_state_lock));
ASSERT(zv->zv_open_count != 1 || RW_READ_HELD(&zv->zv_suspend_lock));

zv->zv_open_count--;
if (zv->zv_open_count == 0)
Expand Down