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nbd: reduce the nbd_index_mutex scope
nbd_index_mutex is currently held over add_disk and inside ->open, which leads to lock order reversals. Refactor the device creation code path so that nbd_dev_add is called without nbd_index_mutex lock held and only takes it for the IDR insertation. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210811124428.2368491-7-hch@lst.de [axboe: fix whitespace] Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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parent
6177b56c96
commit
6e4df4c648
1 changed files with 29 additions and 28 deletions
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@ -1683,7 +1683,7 @@ static const struct blk_mq_ops nbd_mq_ops = {
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.timeout = nbd_xmit_timeout,
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};
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static struct nbd_device *nbd_dev_add(int index)
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static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
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{
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struct nbd_device *nbd;
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struct gendisk *disk;
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@ -1709,6 +1709,7 @@ static struct nbd_device *nbd_dev_add(int index)
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if (err)
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goto out_free_nbd;
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mutex_lock(&nbd_index_mutex);
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if (index >= 0) {
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err = idr_alloc(&nbd_index_idr, nbd, index, index + 1,
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GFP_KERNEL);
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@ -1719,6 +1720,7 @@ static struct nbd_device *nbd_dev_add(int index)
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if (err >= 0)
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index = err;
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}
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mutex_unlock(&nbd_index_mutex);
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if (err < 0)
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goto out_free_tags;
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nbd->index = index;
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@ -1745,7 +1747,7 @@ static struct nbd_device *nbd_dev_add(int index)
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mutex_init(&nbd->config_lock);
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refcount_set(&nbd->config_refs, 0);
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refcount_set(&nbd->refs, 1);
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refcount_set(&nbd->refs, refs);
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INIT_LIST_HEAD(&nbd->list);
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disk->major = NBD_MAJOR;
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disk->first_minor = index << part_shift;
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@ -1849,35 +1851,36 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
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nbd = idr_find(&nbd_index_idr, index);
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}
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if (!nbd) {
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nbd = nbd_dev_add(index);
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if (IS_ERR(nbd)) {
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if (nbd) {
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if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
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test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) {
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nbd->destroy_complete = &destroy_complete;
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mutex_unlock(&nbd_index_mutex);
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/* wait until the nbd device is completely destroyed */
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wait_for_completion(&destroy_complete);
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goto again;
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}
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if (!refcount_inc_not_zero(&nbd->refs)) {
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mutex_unlock(&nbd_index_mutex);
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if (index == -1)
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goto again;
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pr_err("nbd: device at index %d is going down\n",
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index);
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return -EINVAL;
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}
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mutex_unlock(&nbd_index_mutex);
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} else {
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mutex_unlock(&nbd_index_mutex);
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nbd = nbd_dev_add(index, 2);
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if (IS_ERR(nbd)) {
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pr_err("nbd: failed to add new device\n");
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return PTR_ERR(nbd);
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}
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}
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if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
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test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) {
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nbd->destroy_complete = &destroy_complete;
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mutex_unlock(&nbd_index_mutex);
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/* Wait untill the the nbd stuff is totally destroyed */
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wait_for_completion(&destroy_complete);
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goto again;
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}
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if (!refcount_inc_not_zero(&nbd->refs)) {
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mutex_unlock(&nbd_index_mutex);
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if (index == -1)
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goto again;
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printk(KERN_ERR "nbd: device at index %d is going down\n",
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index);
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return -EINVAL;
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}
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mutex_unlock(&nbd_index_mutex);
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mutex_lock(&nbd->config_lock);
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if (refcount_read(&nbd->config_refs)) {
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mutex_unlock(&nbd->config_lock);
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@ -2432,10 +2435,8 @@ static int __init nbd_init(void)
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}
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nbd_dbg_init();
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mutex_lock(&nbd_index_mutex);
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for (i = 0; i < nbds_max; i++)
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nbd_dev_add(i);
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mutex_unlock(&nbd_index_mutex);
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nbd_dev_add(i, 1);
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return 0;
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}
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