On Tue, Aug 16, 2022 at 05:11:31PM +0100, Al Viro wrote:
> filldir_t instances (directory iterators callbacks) used to return 0 for
> "OK, keep going" or -E... for "stop". Note that it's *NOT* how the
> error values are reported - the rules for those are callback-dependent
> and ->iterate{,_shared}() instances only care about zero vs. non-zero
> (look at emit_dir() and friends).
>
> So let's just return bool ("should we keep going?") - it's less confusing
> that way. The choice between "true means keep going" and "true means
> stop" is bikesheddable; we have two groups of callbacks -
> do something for everything in directory, until we run into problem
> and
> find an entry in directory and do something to it.
>
> The former tended to use 0/-E... conventions - -E<something> on failure.
> The latter tended to use 0/1, 1 being "stop, we are done".
> The callers treated anything non-zero as "stop", ignoring which
> non-zero value did they get.
>
> "true means stop" would be more natural for the second group; "true
> means keep going" - for the first one. I tried both variants and
> the things like
> if allocation failed
> something = -ENOMEM;
> return true;
> just looked unnatural and asking for trouble.
I like it the way you have it. My only suggestion is:
+++ b/include/linux/fs.h
@@ -2039,6 +2039,7 @@ extern bool may_open_dev(const struct path *path);
* the kernel specify what kind of dirent layout it wants to have.
* This allows the kernel to read directories into kernel space or
* to have different dirent layouts depending on the binary type.
+ * Return 'true' to keep going and 'false' if there are no more entries.
*/
struct dir_context;
typedef int (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9eced4cc286e..8b8c0c11afec 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2040,7 +2040,7 @@ umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
> * to have different dirent layouts depending on the binary type.
> */
> struct dir_context;
> -typedef int (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
> +typedef bool (*filldir_t)(struct dir_context *, const char *, int, loff_t, u64,
> unsigned);
>
> struct dir_context {
