reduce large do_mount stack usage with noinlines
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>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index db51ddc..63ced21 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -936,8 +936,9 @@
/*
* recursively change the type of the mountpoint.
+ * noinline this do_mount helper to save do_mount stack space.
*/
-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->mnt;
int recurse = flag & MS_REC;
@@ -960,8 +961,10 @@
/*
* do loopback mount.
+ * noinline this do_mount helper to save do_mount stack space.
*/
-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;
@@ -1010,8 +1013,9 @@
* change filesystem flags. dir should be a physical root of filesystem.
* If you've mounted a non-root directory somewhere and want to do remount
* on it - tough luck.
+ * noinline this do_mount helper to save do_mount stack space.
*/
-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;
@@ -1046,7 +1050,10 @@
return 0;
}
-static int do_move_mount(struct nameidata *nd, char *old_name)
+/*
+ * noinline this do_mount helper to save do_mount stack space.
+ */
+static noinline int do_move_mount(struct nameidata *nd, char *old_name)
{
struct nameidata old_nd, parent_nd;
struct vfsmount *p;
@@ -1121,8 +1128,9 @@
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
+ * noinline this do_mount helper to save do_mount stack space.
*/
-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;
