[PATCH 03/24] fs: add a kern_umount helper
From: Christoph Hellwig <hch@lst.de>
Date: 2020-07-20 16:29:58
Also in:
linux-fsdevel, linux-raid, lkml
Subsystem:
abi/api, filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
Like ksys_umount, but takes a kernel pointer for the destination path. Switch over the umount in the init code to it, which just happens to work due to the implicit set_fs(KERNEL_DS) during early init right now. Signed-off-by: Christoph Hellwig <hch@lst.de> --- fs/namespace.c | 53 ++++++++++++++++++++++++---------------- include/linux/fs.h | 1 + include/linux/syscalls.h | 1 - init/do_mounts_initrd.c | 2 +- 4 files changed, 34 insertions(+), 23 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index d208a389aac3c0..cfcee6a1bd5dd2 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c@@ -1706,36 +1706,26 @@ static inline bool may_mandlock(void) } #endif -/* - * Now umount can handle mount points as well as block devices. - * This is important for filesystems which use unnamed block devices. - * - * We now support a flag for forced unmount like the other 'big iron' - * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD - */ +static int umount_lookup_flags(int flags) +{ + if (flags & UMOUNT_NOFOLLOW) + return LOOKUP_MOUNTPOINT; + return LOOKUP_MOUNTPOINT | LOOKUP_FOLLOW; +} -int ksys_umount(char __user *name, int flags) +static int path_umount(struct path *path, int flags) { - struct path path; struct mount *mnt; int retval; - int lookup_flags = LOOKUP_MOUNTPOINT; if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) return -EINVAL; - if (!may_mount()) return -EPERM; - if (!(flags & UMOUNT_NOFOLLOW)) - lookup_flags |= LOOKUP_FOLLOW; - - retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); - if (retval) - goto out; - mnt = real_mount(path.mnt); + mnt = real_mount(path->mnt); retval = -EINVAL; - if (path.dentry != path.mnt->mnt_root) + if (path->dentry != path->mnt->mnt_root) goto dput_and_out; if (!check_mnt(mnt)) goto dput_and_out;
@@ -1748,12 +1738,33 @@ int ksys_umount(char __user *name, int flags) retval = do_umount(mnt, flags); dput_and_out: /* we mustn't call path_put() as that would clear mnt_expiry_mark */ - dput(path.dentry); + dput(path->dentry); mntput_no_expire(mnt); -out: return retval; } +static int ksys_umount(char __user *name, int flags) +{ + struct path path; + int ret; + + ret = user_path_at(AT_FDCWD, name, umount_lookup_flags(flags), &path); + if (ret) + return ret; + return path_umount(&path, flags); +} + +int __init kern_umount(char *name, int flags) +{ + struct path path; + int ret; + + ret = kern_path(name, umount_lookup_flags(flags), &path); + if (ret) + return ret; + return path_umount(&path, flags); +} + SYSCALL_DEFINE2(umount, char __user *, name, int, flags) { return ksys_umount(name, flags);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8f628f9868711d..fbeadaa1a185fb 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -2339,6 +2339,7 @@ extern long do_mount(const char *, const char __user *, const char *, unsigned long, void *); int do_kern_mount(const char *dev_name, const char *dir_name, const char *type_page, unsigned long flags, void *data_page); +int __init kern_umount(char *name, int flags); extern struct vfsmount *collect_mounts(const struct path *); extern void drop_collected_mounts(struct vfsmount *); extern int iterate_mounts(int (*)(struct vfsmount *, void *), void *,
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 5b0f1fca4cfb9d..3b1b8ebcda1d8c 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h@@ -1236,7 +1236,6 @@ asmlinkage long sys_ni_syscall(void); * the ksys_xyzyyz() functions prototyped below. */ -int ksys_umount(char __user *name, int flags); int ksys_chroot(const char __user *filename); ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count); int ksys_chdir(const char __user *filename);
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 604ce78af9acfa..d3858620707893 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c@@ -122,7 +122,7 @@ static void __init handle_initrd(void) else printk("failed\n"); printk(KERN_NOTICE "Unmounting old root\n"); - ksys_umount("/old", MNT_DETACH); + kern_umount("/old", MNT_DETACH); } }
--
2.27.0