[PATCH] reduce large do_mount stack usage with noinlines

Eric Sandeen
2008-02-06T22:14:17Z

do_mount() uses a whopping 616 bytes of stack on x86_64 in
2.6.24-mm1, largely thanks to gcc inlining the various helper
functions.

noinlining these can slim it down a lot; on my box this patch
gets it down to 168, which is mostly the struct nameidata nd;
left on the stack.

These functions are called only as do_mount() helpers;
none of them should be in any path that would see a performance
benefit from inlining...

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

Index: linux-2.6.24-mm1/fs/namespace.c
===================================================================
--- linux-2.6.24-mm1.orig/fs/namespace.c
+++ linux-2.6.24-mm1/fs/namespace.c
@@ -1296,7 +1296,7 @@ out_unlock:
/*
* recursively change the type of the mountpoint.
*/
-static int do_change_type(struct nameidata *nd, int flag)
+static noinline int do_change_type(struct nameidata *nd, int flag)
{
struct vfsmount *m, *mnt = nd->path.mnt;
int recurse = flag & MS_REC;
@@ -1320,7 +1320,7 @@ static int do_change_type(struct nameida
/*
* do loopback mount.
*/
-static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
+static noinline int do_loopback(struct nameidata *nd, char *old_name, int recurse)
{
struct nameidata old_nd;
struct vfsmount *mnt = NULL;
@@ -1387,7 +1387,7 @@ static int change_mount_flags(struct vfs
* If you've mounted a non-root directory somewhere and want to do remount
* on it - tough luck.
*/
-static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
+static noinline int do_remount(struct nameidata *nd, int flags, int mnt_flags,
void *data)
{
int err;
@@ -1425,7 +1425,7 @@ static inline int tree_contains_unbindab
return 0;
}

-static int do_move_mount(struct nameidata *nd, char *old_name)
+static noinline int do_move_mount(struct nameidata *nd, char *old_name)
{
struct nameidata old_nd, parent_nd;
struct vfsmount *p;
@@ -1505,7 +1505,7 @@ out:
* create a new mount for userspace and request it to be added into the
* namespace's tree
*/
-static int do_new_mount(struct nameidata *nd, char *type, int flags,
+static noinline int do_new_mount(struct nameidata *nd, char *type, int flags,
int mnt_flags, char *name, void *data)
{
struct vfsmount *mnt;