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This patch is only appropriate for stable kernels v4.16 - v4.19 Since commit9b30889c54("SUNRPC: Ensure we always close the socket after a connection shuts down"), and until commitc544577dad("SUNRPC: Clean up transport write space handling"), it is possible for the NFS client to spin in the following tight loop: 269.964083: rpc_task_run_action: task:43@0 flags=5a81 state=0005 status=0 action=call_bind [sunrpc] 269.964083: rpc_task_run_action: task:43@0 flags=5a81 state=0005 status=0 action=call_connect [sunrpc] 269.964083: rpc_task_run_action: task:43@0 flags=5a81 state=0005 status=0 action=call_transmit [sunrpc] 269.964085: xprt_transmit: peer=[10.0.1.82]:2049 xid=0x761d3f77 status=-32 269.964085: rpc_task_run_action: task:43@0 flags=5a81 state=0005 status=-32 action=call_transmit_status [sunrpc] 269.964085: rpc_task_run_action: task:43@0 flags=5a81 state=0005 status=-32 action=call_status [sunrpc] 269.964085: rpc_call_status: task:43@0 status=-32 The issue is that the path through call_transmit_status does not release the XPRT_LOCK when the transmit result is -EPIPE, so the socket cannot be properly shut down. The below commit fixed things up in mainline by unconditionally calling xprt_end_transmit() and releasing the XPRT_LOCK after every pass through call_transmit. However, the entirety of this commit is not appropriate for stable kernels because its original inclusion was part of a series that modifies the sunrpc code to use a different queueing model. As a result, there are machinations within this patch that are not needed for a stable fix and will not make sense without a larger backport of the mainline series. In this patch, we take the slightly modified bit of the mainline patch below, which is to release the XPRT_LOCK on transmission error should we detect that the transport is waiting to close. commitc544577dadupstream Author: Trond Myklebust <trond.myklebust@hammerspace.com> Date: Mon Sep 3 23:39:27 2018 -0400 SUNRPC: Clean up transport write space handling Treat socket write space handling in the same way we now treat transport congestion: by denying the XPRT_LOCK until the transport signals that it has free buffer space. Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> The original discussion of the problem is here: https://lore.kernel.org/linux-nfs/20181212135157.4489-1-dwysocha@redhat.com/T/#t This passes my usual cthon and xfstests on NFS as applied on v4.19 mainline. Reported-by: Dave Wysochanski <dwysocha@redhat.com> Suggested-by: Trond Myklebust <trondmy@hammerspace.com> Signed-off-by: Benjamin Coddington <bcodding@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.