Re: [PATCH v1 2/3] Treewide: Stop corrupting socket's task_frag

Paolo Abeni
2022-12-09T12:38:27Z

On Mon, 2022-11-21 at 08:35 -0500, Benjamin Coddington wrote:
> Since moving to memalloc_nofs_save/restore, SUNRPC has stopped setting the
> GFP_NOIO flag on sk_allocation which the networking system uses to decide
> when it is safe to use current->task_frag. The results of this are
> unexpected corruption in task_frag when SUNRPC is involved in memory
> reclaim.
>
> The corruption can be seen in crashes, but the root cause is often
> difficult to ascertain as a crashing machine's stack trace will have no
> evidence of being near NFS or SUNRPC code. I believe this problem to
> be much more pervasive than reports to the community may indicate.
>
> Fix this by having kernel users of sockets that may corrupt task_frag due
> to reclaim set sk_use_task_frag = false. Preemptively correcting this
> situation for users that still set sk_allocation allows them to convert to
> memalloc_nofs_save/restore without the same unexpected corruptions that are
> sure to follow, unlikely to show up in testing, and difficult to bisect.
>
> CC: Philipp Reisner <philipp.reisner@linbit.com>
> CC: Lars Ellenberg <lars.ellenberg@linbit.com>
> CC: "Christoph Böhmwalder" <christoph.boehmwalder@linbit.com>
> CC: Jens Axboe <axboe@kernel.dk>
> CC: Josef Bacik <josef@toxicpanda.com>
> CC: Keith Busch <kbusch@kernel.org>
> CC: Christoph Hellwig <hch@lst.de>
> CC: Sagi Grimberg <sagi@grimberg.me>
> CC: Lee Duncan <lduncan@suse.com>
> CC: Chris Leech <cleech@redhat.com>
> CC: Mike Christie <michael.christie@oracle.com>
> CC: "James E.J. Bottomley" <jejb@linux.ibm.com>
> CC: "Martin K. Petersen" <martin.petersen@oracle.com>
> CC: Valentina Manea <valentina.manea.m@gmail.com>
> CC: Shuah Khan <shuah@kernel.org>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: David Howells <dhowells@redhat.com>
> CC: Marc Dionne <marc.dionne@auristor.com>
> CC: Steve French <sfrench@samba.org>
> CC: Christine Caulfield <ccaulfie@redhat.com>
> CC: David Teigland <teigland@redhat.com>
> CC: Mark Fasheh <mark@fasheh.com>
> CC: Joel Becker <jlbec@evilplan.org>
> CC: Joseph Qi <joseph.qi@linux.alibaba.com>
> CC: Eric Van Hensbergen <ericvh@gmail.com>
> CC: Latchesar Ionkov <lucho@ionkov.net>
> CC: Dominique Martinet <asmadeus@codewreck.org>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: Eric Dumazet <edumazet@google.com>
> CC: Jakub Kicinski <kuba@kernel.org>
> CC: Paolo Abeni <pabeni@redhat.com>
> CC: Ilya Dryomov <idryomov@gmail.com>
> CC: Xiubo Li <xiubli@redhat.com>
> CC: Chuck Lever <chuck.lever@oracle.com>
> CC: Jeff Layton <jlayton@kernel.org>
> CC: Trond Myklebust <trond.myklebust@hammerspace.com>
> CC: Anna Schumaker <anna@kernel.org>
> CC: drbd-dev@lists.linbit.com
> CC: linux-block@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> CC: nbd@other.debian.org
> CC: linux-nvme@lists.infradead.org
> CC: open-iscsi@googlegroups.com
> CC: linux-scsi@vger.kernel.org
> CC: linux-usb@vger.kernel.org
> CC: linux-afs@lists.infradead.org
> CC: linux-cifs@vger.kernel.org
> CC: samba-technical@lists.samba.org
> CC: cluster-devel@redhat.com
> CC: ocfs2-devel@oss.oracle.com
> CC: v9fs-developer@lists.sourceforge.net
> CC: netdev@vger.kernel.org
> CC: ceph-devel@vger.kernel.org
> CC: linux-nfs@vger.kernel.org
>
> Suggested-by: Guillaume Nault <gnault@redhat.com>
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

I think this is the most feasible way out of the existing issue, and I
think this patchset should go via the networking tree, targeting the
Linux 6.2.

If someone has disagreement with the above, please speak!

Thanks,

Paolo