NAME

       nbdkit-noextents-filter - disable extents in the underlying plugin

SYNOPSIS

        nbdkit --filter=noextents plugin

DESCRIPTION

       “Extents” are a feature of the NBD protocol / nbdkit which allow the client to detect
       sparse regions of the underlying disk.  "nbdkit-noextents-filter" disables this so that
       the plugin appears to be fully allocated, at least to a client that requests structured
       replies.  It is also possible to use the --no-sr option to nbdkit to prevent the client
       from using structured replies, which among its other side effects will prevent the client
       from querying extents at all.

       This filter can be useful when combined with nbdkit-file-plugin(1) serving a file from a
       file system known to have poor lseek(2) performance ("tmpfs" is known to be one such
       system).

PARAMETERS

       There are no parameters specific to nbdkit-noextents-filter.  Any parameters are passed
       through to and processed by the underlying plugin in the normal way.

FILES

       $filterdir/nbdkit-noextents-filter.so
           The filter.

           Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION

       "nbdkit-noextents-filter" first appeared in nbdkit 1.14.

SEE ALSO

       nbdkit(1), nbdkit-filter(3), nbdkit-extentlist-filter(1), nbdkit-fua-filter(1),
       nbdkit-nocache-filter(1), nbdkit-noparallel-filter(1), nbdkit-nozero-filter(1),
       nbdkit-file-plugin(1).

AUTHORS

       Richard W.M. Jones

COPYRIGHT

       Copyright (C) 2019 Red Hat Inc.

LICENSE

       Redistribution and use in source and binary forms, with or without modification, are
       permitted provided that the following conditions are met:

       •   Redistributions of source code must retain the above copyright notice, this list of
           conditions and the following disclaimer.

       •   Redistributions in binary form must reproduce the above copyright notice, this list of
           conditions and the following disclaimer in the documentation and/or other materials
           provided with the distribution.

       •   Neither the name of Red Hat nor the names of its contributors may be used to endorse
           or promote products derived from this software without specific prior written
           permission.

       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED
       WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
       FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS
       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
       DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
       OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
       LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
       POSSIBILITY OF SUCH DAMAGE.