Commit 3a18ef5c authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

fs: add ksys_umount() helper; remove in-kernel call to sys_umount() 

Using this helper allows us to avoid the in-kernel call to the sys_umount()
syscall. The ksys_ prefix denotes that this function is meant as a drop-in
replacement for the syscall. In particular, it uses the same calling
convention as ksys_umount().

In the near future, the only fs-external caller of ksys_umount() should be
converted to call do_umount() directly. Then, ksys_umount() can be moved
within sys_umount() again.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net



Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 312db1aa

fs/namespace.c

+7 −2
Original line number Diff line number Diff line
@@ -1680,7 +1680,7 @@ static inline bool may_mandlock(void) 
 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD

 */



SYSCALL_DEFINE2(umount, char __user *, name, int, flags)

int ksys_umount(char __user *name, int flags)

{

	struct path path;

	struct mount *mnt;
@@ -1720,6 +1720,11 @@ out: 
	return retval;

}



SYSCALL_DEFINE2(umount, char __user *, name, int, flags)

{

	return ksys_umount(name, flags);

}



#ifdef __ARCH_WANT_SYS_OLDUMOUNT



/*
@@ -1727,7 +1732,7 @@ out: 
 */

SYSCALL_DEFINE1(oldumount, char __user *, name)

{

	return sys_umount(name, 0);

	return ksys_umount(name, 0);

}



#endif

include/linux/syscalls.h

+1 −0
Original line number Diff line number Diff line
@@ -948,5 +948,6 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, 


int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,

	       unsigned long flags, void __user *data);

int ksys_umount(char __user *name, int flags);



#endif

init/do_mounts_initrd.c

+1 −1
Original line number Diff line number Diff line
@@ -105,7 +105,7 @@ static void __init handle_initrd(void) 
		else

			printk("failed\n");

		printk(KERN_NOTICE "Unmounting old root\n");

		sys_umount("/old", MNT_DETACH);

		ksys_umount("/old", MNT_DETACH);

		printk(KERN_NOTICE "Trying to free ramdisk memory ... ");

		if (fd < 0) {

			error = fd;

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