From: ASANO Masahiro <masano@tnes.nec.co.jp>
Date: Wed, 23 Aug 2006 00:06:02 +0000 (-0400)
Subject: VFS: add lookup hint for network file systems
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=a634904a7de0d3a0bc606f608007a34e8c05bfee;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

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 55a131230f9..863166441bf 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1767,6 +1767,8 @@ struct dentry *lookup_create(struct nameidata *nd, int is_dir)
 	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.