Re: sporadic hangs on generic/186

["J. Bruce Fields" <bfields@fieldses.org>]

On Thu, Apr 07, 2022 at 11:19:34AM +1000, NeilBrown wrote:
> I had a look through the various places where alloc can now fail.
> 
> I think xdr_alloc_bvec() in xprt_sent_pagedata() is the most likely
> cause of a problem here.  I don't think an -ENOMEM from there is caught,
> so it could likely filter up to NFS and result in the message you got.
> 
> I don't think we can easily handle failure there.  We need to stay with
> GFP_KERNEL rely on PF_MEMALLOC to make forward progress for
> swap-over-NFS.
> 
> Bruce: can you change that one line back to GFP_KERNEL and see if the
> problem goes away?

Like this?  Sure--might take me a day or two to run the tests and get
results back.--b.

diff --git a/net/sunrpc/socklib.c b/net/sunrpc/socklib.c
index 05b38bf68316..506627dc9a0f 100644
--- a/net/sunrpc/socklib.c
+++ b/net/sunrpc/socklib.c
@@ -223,7 +223,7 @@ static int xprt_send_pagedata(struct socket *sock, struct msghdr *msg,
 {
 	int err;
 
-	err = xdr_alloc_bvec(xdr, rpc_task_gfp_mask());
+	err = xdr_alloc_bvec(xdr, GFP_KERNEL);
 	if (err < 0)
 		return err;