nfsd: increase DRC cache limit

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>

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 7e3af3e..6bbc717 100644 (file)
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -446,7 +446,7 @@ void nfsd_reset_versions(void)
  */
 static void set_max_drc(void)
 {
-       #define NFSD_DRC_SIZE_SHIFT     10
+       #define NFSD_DRC_SIZE_SHIFT     7
        nfsd_drc_max_mem = (nr_free_buffer_pages()
                                        >> NFSD_DRC_SIZE_SHIFT) * PAGE_SIZE;
        nfsd_drc_mem_used = 0;