On Sun, 08 Sep 2013 16:47:15 +0800
Ian Kent <raven@xxxxxxxxxx> wrote:
> The function user_path_umountat() not only avoids revalidation but
> avoids the managed dentry code as well.
>
> This function has other uses, such as the case where autofs is
> reconnecting to a tree of mounts and needs to avoid the managed
> dentry call since that would incorrectly cause a callback to the
> daemon.
>
> So give the function a more descriptive name.
>
> Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> fs/namei.c | 34 +++++++++++++++++++---------------
> fs/namespace.c | 2 +-
> include/linux/namei.h | 2 +-
> 3 files changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index f415c66..24f7562 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2250,7 +2250,7 @@ user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
> * to the link, and nd->path will *not* be put.
> */
> static int
> -umount_lookup_last(struct nameidata *nd, struct path *path)
> +mntpoint_lookup_last(struct nameidata *nd, struct path *path)
> {
> int error = 0;
> struct dentry *dentry;
> @@ -2309,17 +2309,19 @@ error_check:
> }
>
> /**
> - * path_umountat - look up a path to be umounted
> + * path_mntpointat - look up a path to a mount point
> * @dfd: directory file descriptor to start walk from
> * @name: full pathname to walk
> * @flags: lookup flags
> * @nd: pathwalk nameidata
> *
> - * Look up the given name, but don't attempt to revalidate the last component.
> + * Look up the given name, but don't attempt to revalidate the last component
> + * or call the managed dentry code.
> * Returns 0 and "path" will be valid on success; Retuns error otherwise.
> */
> static int
> -path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
> +path_mntpointat(int dfd, const char *name,
> + struct path *path, unsigned int flags)
> {
> struct file *base = NULL;
> struct nameidata nd;
> @@ -2343,7 +2345,7 @@ path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
> }
> }
>
> - err = umount_lookup_last(&nd, path);
> + err = mntpoint_lookup_last(&nd, path);
> while (err > 0) {
> void *cookie;
> struct path link = *path;
> @@ -2354,7 +2356,7 @@ path_umountat(int dfd, const char *name, struct path *path, unsigned int flags)
> err = follow_link(&link, &nd, &cookie);
> if (err)
> break;
> - err = umount_lookup_last(&nd, path);
> + err = mntpoint_lookup_last(&nd, path);
> put_link(&nd, &link, cookie);
> }
> out:
> @@ -2368,21 +2370,23 @@ out:
> }
>
> /**
> - * user_path_umountat - lookup a path from userland in order to umount it
> + * user_path_mntpointat - lookup a mountpoint path from userland without
> + * revalidating it or calling the managed dentry code
> * @dfd: directory file descriptor
> * @name: pathname from userland
> * @flags: lookup flags
> * @path: pointer to container to hold result
> *
> - * A umount is a special case for path walking. We're not actually interested
> - * in the inode in this situation, and ESTALE errors can be a problem. We
> - * simply want track down the dentry and vfsmount attached at the mountpoint
> - * and avoid revalidating the last component.
> + * A mount point (when being umounted for example) is a special case for path
> + * walking. We're not actually interested in the inode in this situation, and
> + * ESTALE errors can be a problem. We simply want track down the dentry and
> + * vfsmount attached at the mountpoint and avoid revalidating or calling the
> + * managed dentry code for the last component.
> *
> * Returns 0 and populates "path" on success.
> */
> int
> -user_path_umountat(int dfd, const char __user *name, unsigned int flags,
> +user_path_mntpointat(int dfd, const char __user *name, unsigned int flags,
> struct path *path)
> {
> struct filename *s = getname(name);
> @@ -2391,11 +2395,11 @@ user_path_umountat(int dfd, const char __user *name, unsigned int flags,
> if (IS_ERR(s))
> return PTR_ERR(s);
>
> - error = path_umountat(dfd, s->name, path, flags | LOOKUP_RCU);
> + error = path_mntpointat(dfd, s->name, path, flags | LOOKUP_RCU);
> if (unlikely(error == -ECHILD))
> - error = path_umountat(dfd, s->name, path, flags);
> + error = path_mntpointat(dfd, s->name, path, flags);
> if (unlikely(error == -ESTALE))
> - error = path_umountat(dfd, s->name, path, flags | LOOKUP_REVAL);
> + error = path_mntpointat(dfd, s->name, path, flags|LOOKUP_REVAL);
>
> if (likely(!error))
> audit_inode(s, path->dentry, 0);
> diff --git a/fs/namespace.c b/fs/namespace.c
> index fc2b522..c48ad96 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1321,7 +1321,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
> if (!(flags & UMOUNT_NOFOLLOW))
> lookup_flags |= LOOKUP_FOLLOW;
>
> - retval = user_path_umountat(AT_FDCWD, name, lookup_flags, &path);
> + retval = user_path_mntpointat(AT_FDCWD, name, lookup_flags, &path);
> if (retval)
> goto out;
> mnt = real_mount(path.mnt);
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index cd09751..7908abf 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -58,7 +58,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
>
> extern int user_path_at(int, const char __user *, unsigned, struct path *);
> extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
> -extern int user_path_umountat(int, const char __user *, unsigned int, struct path *);
> +extern int user_path_mntpointat(int, const char __user *, unsigned int, struct path *);
>
> #define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path)
> #define user_lpath(name, path) user_path_at(AT_FDCWD, name, 0, path)
>
Looks good to me.
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
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