nfsd: add a new struct file caching facility to nfsd

Currently, NFSv2/3 reads and writes have to open a file, do the read or
write and then close it again for each RPC. This is highly inefficient,
especially when the underlying filesystem has a relatively slow open
routine.

This patch adds a new open file cache to knfsd. Rather than doing an
open for each RPC, the read/write handlers can call into this cache to
see if there is one already there for the correct filehandle and
NFS_MAY_READ/WRITE flags.

If there isn't an entry, then we create a new one and attempt to
perform the open. If there is, then we wait until the entry is fully
instantiated and return it if it is at the end of the wait. If it's
not, then we attempt to take over construction.

Since the main goal is to speed up NFSv2/3 I/O, we don't want to
close these files on last put of these objects. We need to keep them
around for a little while since we never know when the next READ/WRITE
will come in.

Cache entries have a hardcoded 1s timeout, and we have a recurring
workqueue job that walks the cache and purges any entries that have
expired.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Richard Sharpe <richard.sharpe@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 18d94ea984ba..a6b1eab7b722 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -27,6 +27,7 @@
 #include "cache.h"
 #include "vfs.h"
 #include "netns.h"
+#include "filecache.h"
 
 #define NFSDDBG_FACILITY	NFSDDBG_SVC
 
@@ -313,6 +314,9 @@ static int nfsd_startup_generic(int nrservs)
 	if (nfsd_users++)
 		return 0;
 
+	ret = nfsd_file_cache_init();
+	if (ret)
+		goto dec_users;
 	/*
 	 * Readahead param cache - will no-op if it already exists.
 	 * (Note therefore results will be suboptimal if number of
@@ -320,7 +324,7 @@ static int nfsd_startup_generic(int nrservs)
 	 */
 	ret = nfsd_racache_init(2*nrservs);
 	if (ret)
-		goto dec_users;
+		goto out_file_cache;
 
 	ret = nfs4_state_start();
 	if (ret)
@@ -329,6 +333,8 @@ static int nfsd_startup_generic(int nrservs)
 
 out_racache:
 	nfsd_racache_shutdown();
+out_file_cache:
+	nfsd_file_cache_shutdown();
 dec_users:
 	nfsd_users--;
 	return ret;
@@ -340,6 +346,7 @@ static void nfsd_shutdown_generic(void)
 		return;
 
 	nfs4_state_shutdown();
+	nfsd_file_cache_shutdown();
 	nfsd_racache_shutdown();
 }