From: Christoph Hellwig <hch@lst.de>
Date: Wed, 25 Aug 2021 18:31:07 +0200
Subject: [PATCH] nbd: only return usable devices from nbd_find_unused
Git-commit: 438cd318c8dfa5228ffd43af1b98d7cd7d92e1c6
Patch-mainline: v5.15-rc1
References: jsc#PED-1183
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>
Link: https://lore.kernel.org/r/20210825163108.50713-6-hch@lst.de
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
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 6a832bf81647..70dc9d80a173 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1790,16 +1790,20 @@ 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;
}
@@ -1873,10 +1877,10 @@ 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;
@@ -1889,8 +1893,6 @@ 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;
--
2.35.3