VFS: add lookup hint for network file systems
I'm trying to speeding up mkdir(2) for network file systems. A typical
mkdir(2) calls two inode_operations: lookup and mkdir. The lookup
operation would fail with ENOENT in common case. I think it is unnecessary
because the subsequent mkdir operation can check it. In case of creat(2),
lookup operation is called with the LOOKUP_CREATE flag, so individual
filesystem can omit real lookup. e.g. nfs_lookup().
Here is a sample patch which uses LOOKUP_CREATE and O_EXCL on mkdir,
symlink and mknod. This uses the gadget for creat(2).
And here is the result of a benchmark on NFSv3.
mkdir(2) 10,000 times:
original 50.5 sec
patched 29.0 sec
Signed-off-by: ASANO Masahiro <masano@tnes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
(cherry picked from fab7bf44449b29f9d5572a5dd8adcf7c91d5bf0f commit)
diff --git a/fs/namei.c b/fs/namei.c
index 55a1312..8631664 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1767,6 +1767,8 @@
if (nd->last_type != LAST_NORM)
goto fail;
nd->flags &= ~LOOKUP_PARENT;
+ nd->flags |= LOOKUP_CREATE;
+ nd->intent.open.flags = O_EXCL;
/*
* Do the final lookup.
