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Commit 2dafe1c4 authored by Eric Sandeen's avatar Eric Sandeen Committed by Linus Torvalds
Browse files

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: default avatarEric Sandeen <sandeen@redhat.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ac2a6599

fs/namespace.c

+13 −5
Original line number Diff line number Diff line
@@ -936,8 +936,9 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) 


/*

 * 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 @@ static int do_change_type(struct nameidata *nd, int flag) 


/*

 * 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 @@ static int do_loopback(struct nameidata *nd, char *old_name, int recurse) 
 * 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 @@ static inline int tree_contains_unbindable(struct vfsmount *mnt) 
	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 @@ static int do_move_mount(struct nameidata *nd, char *old_name) 
/*

 * 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;