[PATCH 5/6] nbd: only return usable devices from nbd_find_unused
From: Christoph Hellwig <hch@lst.de>
Date: 2021-08-25 16:42:10
Subsystem:
block layer, network block device (nbd), the rest · Maintainers:
Jens Axboe, Josef Bacik, Linus Torvalds
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