5.4-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 62a8642ba00aa8ceb0a02ade942f5ec52e877c95 ]
nfsd4_shutdown_copy() is just this:
while ((copy = nfsd4_get_copy(clp)) != NULL) nfsd4_stop_copy(copy);
nfsd4_get_copy() bumps @copy's reference count, preventing nfsd4_stop_copy() from releasing @copy.
A while loop like this usually works by removing the first element of the list, but neither nfsd4_get_copy() nor nfsd4_stop_copy() alters the async_copies list.
Best I can tell, then, is that nfsd4_shutdown_copy() continues to loop until other threads manage to remove all the items from this list. The spinning loop blocks shutdown until these items are gone.
Possibly the reason we haven't seen this issue in the field is because client_has_state() prevents __destroy_client() from calling nfsd4_shutdown_copy() if there are any items on this list. In a subsequent patch I plan to remove that restriction.
Fixes: e0639dc5805a ("NFSD introduce async copy feature") Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfsd/nfs4proc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index 27e9754ad3b9d..3bae364048f6f 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1117,7 +1117,7 @@ static void nfsd4_stop_copy(struct nfsd4_copy *copy) nfs4_put_copy(copy); }
-static struct nfsd4_copy *nfsd4_get_copy(struct nfs4_client *clp) +static struct nfsd4_copy *nfsd4_unhash_copy(struct nfs4_client *clp) { struct nfsd4_copy *copy = NULL;
@@ -1126,6 +1126,9 @@ static struct nfsd4_copy *nfsd4_get_copy(struct nfs4_client *clp) copy = list_first_entry(&clp->async_copies, struct nfsd4_copy, copies); refcount_inc(©->refcount); + copy->cp_clp = NULL; + if (!list_empty(©->copies)) + list_del_init(©->copies); } spin_unlock(&clp->async_lock); return copy; @@ -1135,7 +1138,7 @@ void nfsd4_shutdown_copy(struct nfs4_client *clp) { struct nfsd4_copy *copy;
- while ((copy = nfsd4_get_copy(clp)) != NULL) + while ((copy = nfsd4_unhash_copy(clp)) != NULL) nfsd4_stop_copy(copy); }