Quoting Aditya Kali (adityakali@xxxxxxxxxx):
> The new function kernfs_path_from_node() generates and returns
> kernfs path of a given kernfs_node relative to a given parent
> kernfs_node.
>
> Signed-off-by: Aditya Kali <adityakali@xxxxxxxxxx>
Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
(with or without my comment below taken)
> ---
> fs/kernfs/dir.c | 53 ++++++++++++++++++++++++++++++++++++++++----------
> include/linux/kernfs.h | 3 +++
> 2 files changed, 46 insertions(+), 10 deletions(-)
>
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index a693f5b..8655485 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -44,14 +44,24 @@ static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
> return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
> }
>
> -static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
> - size_t buflen)
> +static char * __must_check kernfs_path_from_node_locked(
> + struct kernfs_node *kn_root,
> + struct kernfs_node *kn,
> + char *buf,
> + size_t buflen)
> {
> char *p = buf + buflen;
> int len;
>
> + BUG_ON(!buflen);
> +
> *--p = '\0';
>
> + if (kn == kn_root) {
> + *--p = '/';
> + return p;
> + }
> +
> do {
> len = strlen(kn->name);
> if (p - buf < len + 1) {
> @@ -63,6 +73,8 @@ static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
> memcpy(p, kn->name, len);
> *--p = '/';
> kn = kn->parent;
> + if (kn == kn_root)
> + break;
I wonder if it would be clearer if you instead changed the while condition, i.e.
} while (kn && kn != kn_root && kn_parent);
i.e .it's not a special condition, just a part of the expected flow.
> } while (kn && kn->parent);
>
> return p;
> @@ -92,26 +104,47 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
> }
>
> /**
> - * kernfs_path - build full path of a given node
> + * kernfs_path_from_node - build path of node @kn relative to @kn_root.
> + * @kn_root: parent kernfs_node relative to which we need to build the path
> * @kn: kernfs_node of interest
> - * @buf: buffer to copy @kn's name into
> + * @buf: buffer to copy @kn's path into
> * @buflen: size of @buf
> *
> - * Builds and returns the full path of @kn in @buf of @buflen bytes. The
> - * path is built from the end of @buf so the returned pointer usually
> + * Builds and returns @kn's path relative to @kn_root. @kn_root is expected to
> + * be parent of @kn at some level. If this is not true or if @kn_root is NULL,
> + * then full path of @kn is returned.
> + * The path is built from the end of @buf so the returned pointer usually
> * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
> * and %NULL is returned.
> */
> -char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
> +char *kernfs_path_from_node(struct kernfs_node *kn_root, struct kernfs_node *kn,
> + char *buf, size_t buflen)
> {
> unsigned long flags;
> char *p;
>
> spin_lock_irqsave(&kernfs_rename_lock, flags);
> - p = kernfs_path_locked(kn, buf, buflen);
> + p = kernfs_path_from_node_locked(kn_root, kn, buf, buflen);
> spin_unlock_irqrestore(&kernfs_rename_lock, flags);
> return p;
> }
> +EXPORT_SYMBOL_GPL(kernfs_path_from_node);
> +
> +/**
> + * kernfs_path - build full path of a given node
> + * @kn: kernfs_node of interest
> + * @buf: buffer to copy @kn's name into
> + * @buflen: size of @buf
> + *
> + * Builds and returns the full path of @kn in @buf of @buflen bytes. The
> + * path is built from the end of @buf so the returned pointer usually
> + * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
> + * and %NULL is returned.
> + */
> +char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
> +{
> + return kernfs_path_from_node(NULL, kn, buf, buflen);
> +}
> EXPORT_SYMBOL_GPL(kernfs_path);
>
> /**
> @@ -145,8 +178,8 @@ void pr_cont_kernfs_path(struct kernfs_node *kn)
>
> spin_lock_irqsave(&kernfs_rename_lock, flags);
>
> - p = kernfs_path_locked(kn, kernfs_pr_cont_buf,
> - sizeof(kernfs_pr_cont_buf));
> + p = kernfs_path_from_node_locked(NULL, kn, kernfs_pr_cont_buf,
> + sizeof(kernfs_pr_cont_buf));
> if (p)
> pr_cont("%s", p);
> else
> diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> index 30faf79..3c2be75 100644
> --- a/include/linux/kernfs.h
> +++ b/include/linux/kernfs.h
> @@ -258,6 +258,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
> }
>
> int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
> +char * __must_check kernfs_path_from_node(struct kernfs_node *root_kn,
> + struct kernfs_node *kn, char *buf,
> + size_t buflen);
> char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
> size_t buflen);
> void pr_cont_kernfs_name(struct kernfs_node *kn);
> --
> 2.1.0.rc2.206.gedb03e5
>
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