An NFSv4.1+ client negotiates the size of its duplicate reply cache size
in the initial CREATE_SESSION request. The server preallocates the
memory for the duplicate reply cache to ensure that we'll never fail to
record the response to a nonidempotent operation.
To prevent a few CREATE_SESSIONs from consuming all of memory we set an
upper limit based on nr_free_buffer_pages(). 1/2^10 has been too
limiting in practice; 1/2^7 is still less than one percent.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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