netdev - Re: [PATCH] Fix oops in NFS

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Message-ID: <ZZg6XQOjlOA0CL17@codewreck.org>
Date: Sat, 6 Jan 2024 02:20:29 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: Matthew Wilcox <willy@...radead.org>,
	David Howells <dhowells@...hat.com>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Anna Schumaker <Anna.Schumaker@...app.com>,
	Trond Myklebust <trond.myklebust@...merspace.com>,
	Jeff Layton <jlayton@...nel.org>, Steve French <smfrench@...il.com>,
	Marc Dionne <marc.dionne@...istor.com>,
	Paulo Alcantara <pc@...guebit.com>,
	Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
	Eric Van Hensbergen <ericvh@...nel.org>,
	Ilya Dryomov <idryomov@...il.com>,
	Christian Brauner <christian@...uner.io>, linux-cachefs@...hat.com,
	linux-afs@...ts.infradead.org, linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org, ceph-devel@...r.kernel.org,
	v9fs@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix oops in NFS

Matthew Wilcox wrote on Fri, Jan 05, 2024 at 01:17:36PM +0000:
> host on /host type 9p (rw,relatime,access=client,trans=virtio)

David Howells wrote on Fri, Jan 05, 2024 at 02:33:32PM +0000:
> > This commit (100ccd18bb41 in linux-next 20240104) is bad for me.  After
> > it, running xfstests gives me first a bunch of errors along these lines:
> 
> This may be related to a patch that is in linux-next 20240105, but not
> 20240104 ("9p: Fix initialisation of netfs_inode for 9p").

Yes, you'd be reading zeroes without that patch because the netfs code
thinks the file has 0 size and doesn't bother reading, that'd explain
the exec format error loading other modules...

One thing that surprised me is that this also affects cache=none, I
thought we had different file ops going straight to p9_client_read in
this case?
But turning my brain on this would be the read-only mmap case that we
need to support for execs, which module loading also uses, so this came
biting there alright.

-- 
Dominique Martinet | Asmadeus