=head1 NAME

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

=head1 SYNOPSIS

 nbdkit --filter=noextents plugin

=head1 DESCRIPTION

“Extents” are a feature of the NBD protocol / nbdkit which allow the
client to detect sparse regions of the underlying disk.
C<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 I<--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 L<nbdkit-file-plugin(1)>
serving a file from a file system known to have poor C<lseek(2)>
performance (C<tmpfs> is known to be one such system).

=head1 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.

=head1 FILES

=over 4

=item F<$filterdir/nbdkit-noextents-filter.so>

The filter.

Use C<nbdkit --dump-config> to find the location of C<$filterdir>.

=back

=head1 VERSION

C<nbdkit-noextents-filter> first appeared in nbdkit 1.14.

=head1 SEE ALSO

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

=head1 AUTHORS

Richard W.M. Jones

=head1 COPYRIGHT

Copyright (C) 2019 Red Hat Inc.
