On Tue, 18 Mar 2025 at 20:45, James Bottomley
<James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
> The current iterate_dir() infrastructure is somewhat cumbersome to use
> from within the kernel. Introduce a lighter weight
> simple_iterate_dir() function that directly iterates the directory and
> executes a callback for each positive dentry.
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> ---
> fs/libfs.c | 33 +++++++++++++++++++++++++++++++++
> include/linux/fs.h | 2 ++
> 2 files changed, 35 insertions(+)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 816bfe6c0430..37da5fe25242 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -214,6 +214,39 @@ static void internal_readdir(struct dentry *dentry, struct dentry *cursor,
> dput(next);
> }
>
> +/**
> + * generic_iterate_call - iterate all entries executing @callback
This name doesn't match the name below.
> + *
> + * @dir: directory to iterate over
> + * @data: data passed to callback
> + * @callback: callback to call
> + *
> + * Iterates over all positive dentries that are direct children of
> + * @dir (so doesn't include . and ..) and executes the callback for
> + * each of them. Note that because there's no struct *mnt, the caller
> + * is responsible for pinning the filesystem.
> + *
> + * If the @callback returns true, the iteration will continue and if
> + * it returns @false, it will stop (note that since the cursor is
> + * destroyed the next invocation will go back to the beginning again).
> + *
> + */
> +int simple_iterate_call(struct dentry *dir, void *data,
> + bool (*callback)(void *, struct dentry *))
> +{
> + struct dentry *cursor = d_alloc_cursor(dir);
> +
> + if (!cursor)
> + return -ENOMEM;
> +
> + internal_readdir(dir, cursor, data, true, callback);
> +
> + dput(cursor);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(simple_iterate_call);
> +
> static bool dcache_readdir_callback(void *data, struct dentry *entry)
> {
> struct dir_context *ctx = data;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 2788df98080f..a84896f0b2d1 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3531,6 +3531,8 @@ extern int simple_rename(struct mnt_idmap *, struct inode *,
> unsigned int);
> extern void simple_recursive_removal(struct dentry *,
> void (*callback)(struct dentry *));
> +extern int simple_iterate_call(struct dentry *dir, void *data,
> + bool (*callback)(void *, struct dentry *));
> extern int noop_fsync(struct file *, loff_t, loff_t, int);
> extern ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
> extern int simple_empty(struct dentry *);
> --
> 2.43.0
>
