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fs: refactor ksys_umount

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Factor out a path_umount helper that takes a struct path * instead of the
actual file name.  This will allow to convert the init and devtmpfs code
to properly mount based on a kernel pointer instead of relying on the
implicit set_fs(KERNEL_DS) during early init.

Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Christoph Hellwig 2020-07-21 10:54:34 +02:00
parent a1e6aaa374
commit 41525f56e2
1 changed files with 18 additions and 22 deletions
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40
fs/namespace.c
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@ -1706,36 +1706,19 @@ 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
*/
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 +1731,25 @@ 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;
}
int ksys_umount(char __user *name, int flags)
{
int lookup_flags = LOOKUP_MOUNTPOINT;
struct path path;
int ret;
if (!(flags & UMOUNT_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
if (ret)
return ret;
return path_umount(&path, flags);
}
SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
{
return ksys_umount(name, flags);