[PATCH] Access cache forgetting mode bits

[Steve Dickson <SteveD@redhat.com>]

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While debugging something else, I notice that every time
I did a ls on a nfs mounted directory a wto ACCESS rpc was
*always* happening (with a  2.4.21 kernel). Taking a closer
look it turns out the access cache  was dropping previous
access bits. Here is the scenario...

nfs_permission is called with mode = MAY_EXEC
the cached value is Zero so an ACCESS rpc is done.
after the rpc, the cached value is _set_ to MAY_EXEC

then nfs_permission is called with mode = MAY_READ
the cached value is MAY_EXEC, so an ACCESS rpc is done.
after the rpc, the cache value is _set_ to MAY_READ

again, nfs_permission is called with mode = MAY_EXEC
this time the cached value is MAY_READ so _again_ an RPC is done
after the rpc, the cached value is _set_ to MAY_EXEC

Its a vicious cycle...

So this patch changes the setting of the masked value
to the or-ing of the masked value. This cause the
previous bits to be remembered thus cutting down on
the number of otw rpcs...


SteveD.

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--- linux-2.4.21/fs/nfs/dir.c.diff	2003-08-28 12:13:22.000000000 -0400
+++ linux-2.4.21/fs/nfs/dir.c	2003-08-28 12:13:47.000000000 -0400
@@ -1278,7 +1278,7 @@ nfs_permission(struct inode *inode, int 
 		if (cache->cred)
 			put_rpccred(cache->cred);
 		cache->cred = cred;
-		cache->mask = mask;
+		cache->mask |= mask;
 		cache->err = error;
 		return error;
 	}