[PATCH 5/6] nbd: only return usable devices from nbd_find_unused
Device marked as NBD_DESTROY_ON_DISCONNECT can and should be skipped
given that they won't survive the disconnect. So skip them and try
to grab a reference directly and just continue if the the devices
is being torn down or created and thus has a zero refcount.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/block/nbd.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 042af761d3a4..5c03f3eb3129 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1794,16 +1794,20 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
return ERR_PTR(err);
}
-static struct nbd_device *nbd_find_unused(void)
+static struct nbd_device *nbd_find_get_unused(void)
{
struct nbd_device *nbd;
int id;
lockdep_assert_held(&nbd_index_mutex);
- idr_for_each_entry(&nbd_index_idr, nbd, id)
- if (!refcount_read(&nbd->config_refs))
+ idr_for_each_entry(&nbd_index_idr, nbd, id) {
+ if (refcount_read(&nbd->config_refs) ||
+ test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))
+ continue;
+ if (refcount_inc_not_zero(&nbd->refs))
return nbd;
+ }
return NULL;
}
@@ -1877,10 +1881,10 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
again:
mutex_lock(&nbd_index_mutex);
if (index == -1)
- nbd = nbd_find_unused();
+ nbd = nbd_find_get_unused();
else
nbd = idr_find(&nbd_index_idr, index);
- if (nbd) {
+ if (nbd && index != -1) {
if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) {
nbd->destroy_complete = &destroy_complete;
@@ -1893,8 +1897,6 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
if (!refcount_inc_not_zero(&nbd->refs)) {
mutex_unlock(&nbd_index_mutex);
- if (index == -1)
- goto again;
pr_err("nbd: device at index %d is going down\n",
index);
return -EINVAL;
--
2.30.2
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