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Date:   Wed, 6 Apr 2022 21:49:39 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     NeilBrown <neilb@suse.de>
Cc:     Dave Chinner <david@fromorbit.com>,
        Trond Myklebust <trondmy@hammerspace.com>,
        Chuck Lever <chuck.lever@oracle.com>,
        linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: sporadic hangs on generic/186
Message-ID: <20220407014939.GC1242@fieldses.org>
References: <20220406195424.GA1242@fieldses.org>
 <20220407001453.GE1609613@dread.disaster.area>
 <164929126156.10985.11316778982526844125@noble.neil.brown.name>
 <164929437439.10985.5253499040284089154@noble.neil.brown.name>
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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;