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d3684397ea
Previously nfs_local_probe() was made to disable and then attempt to re-enable LOCALIO (via LOCALIO protocol handshake) if/when it was called and LOCALIO already enabled. Vague memory for _why_ this was the case is that this was useful if/when a local NFS server were to be restarted with a local NFS client connected to it. But as it happens this causes an absurd amount of LOCALIO flapping which has a side-effect of too much IO being needlessly sent to NFSD (using RPC over the loopback network interface). This is the definition of "serious performance loss" (that negates the point of having LOCALIO). So remove this mis-optimization for re-enabling LOCALIO if/when an NFS server is restarted (which is an extremely rare thing to do). Will revisit testing that scenario again but in the meantime this patch restores the full benefit of LOCALIO. Signed-off-by: Mike Snitzer <snitzer@kernel.org> Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: NeilBrown <neil@brown.name> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
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 reStructuredText markup notation.
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.