Re: [PATCH 1/1] fs: add 4th case to do_path_lookup

[Andrew Morton <akpm@linux-foundation.org>]

On Sun, 29 Apr 2007 23:30:12 -0400 Josef Sipek <jsipek@cs.sunysb.edu> wrote:

> Signed-off-by: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 2995fba..1516a9b 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1125,6 +1125,10 @@ static int fastcall do_path_lookup(int dfd, const char *name,
>  		nd->mnt = mntget(fs->rootmnt);
>  		nd->dentry = dget(fs->root);
>  		read_unlock(&fs->lock);
> +	} else if (flags & LOOKUP_ONE) {
> +		/* nd->mnt and nd->dentry already set, just grab references */
> +		mntget(nd->mnt);
> +		dget(nd->dentry);
>  	} else if (dfd == AT_FDCWD) {
>  		read_lock(&fs->lock);
>  		nd->mnt = mntget(fs->pwdmnt);
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index 92b422b..aa89d97 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -48,6 +48,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
>   *  - internal "there are more path compnents" flag
>   *  - locked when lookup done with dcache_lock held
>   *  - dentry cache is untrusted; force a real lookup
> + *  - lookup path from given dentry/vfsmount pair
>   */
>  #define LOOKUP_FOLLOW		 1
>  #define LOOKUP_DIRECTORY	 2
> @@ -55,6 +56,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
>  #define LOOKUP_PARENT		16
>  #define LOOKUP_NOALT		32
>  #define LOOKUP_REVAL		64
> +#define LOOKUP_ONE	       128

Well the patch passes my too-small-to-care-about test ;)

Unless someone objects I'd suggest that you add it to the unionfs tree.