From: Jeff Layton Date: Tue, 11 Dec 2012 13:56:16 +0000 (-0500) Subject: vfs: remove unneeded permission check from path_init X-Git-Tag: v3.8-rc1~13^2~55 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=582aa64a04a579d47d05e4a0ee85bf047978ef4d;p=platform%2Fkernel%2Flinux-3.10.git vfs: remove unneeded permission check from path_init When path_init is called with a valid dfd, that code checks permissions on the open directory fd and returns an error if the check fails. This permission check is redundant, however. Both callers of path_init immediately call link_path_walk afterward. The first thing that link_path_walk does for pathnames that do not consist only of slashes is to check for exec permissions at the starting point of the path walk. And this check in path_init() is on the path taken only when *name != '/' && *name != '\0'. In most cases, these checks are very quick, but when the dfd is for a file on a NFS mount with the actimeo=0, each permission check goes out onto the wire. The result is 2 identical ACCESS calls. Given that these codepaths are fairly "hot", I think it makes sense to eliminate the permission check in path_init and simply assume that the caller will eventually check the permissions before proceeding. Reported-by: Dave Wysochanski Signed-off-by: Jeff Layton Signed-off-by: Al Viro --- diff --git a/fs/namei.c b/fs/namei.c index 5f4cdf3..e245d88 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1903,6 +1903,7 @@ static int path_init(int dfd, const char *name, unsigned int flags, get_fs_pwd(current->fs, &nd->path); } } else { + /* Caller must check execute permissions on the starting path component */ struct fd f = fdget_raw(dfd); struct dentry *dentry; @@ -1916,12 +1917,6 @@ static int path_init(int dfd, const char *name, unsigned int flags, fdput(f); return -ENOTDIR; } - - retval = inode_permission(dentry->d_inode, MAY_EXEC); - if (retval) { - fdput(f); - return retval; - } } nd->path = f.file->f_path;