Hey Gabriel,
On Mon, 2020-04-13 at 12:53 -0400, Gabriel Krisman Bertazi wrote:
> A filesystem configuration utility has no way to detect which filename
> encodings are supported by the running kernel. This means, for
> instance, mkfs has no way to tell if the generated filesystem will be
> mountable in the current kernel or not. Also, users have no easy way to
> know if they can update the encoding in their filesystems and still have
> something functional in the end.
>
> This exposes details of the encodings available in the unicode
> subsystem, to fill that gap.
>
> Cc: Theodore Ts'o <tytso@xxxxxxx>
> Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>
> ---
> Changes since v1:
> - Make init functions static. (lkp)
>
> Documentation/ABI/testing/sysfs-fs-unicode | 13 +++++
> fs/unicode/utf8-core.c | 64 ++++++++++++++++++++++
> fs/unicode/utf8-norm.c | 18 ++++++
> fs/unicode/utf8n.h | 5 ++
> 4 files changed, 100 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-fs-unicode
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-unicode b/Documentation/ABI/testing/sysfs-fs-unicode
> new file mode 100644
> index 000000000000..15c63367bb8e
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-fs-unicode
> @@ -0,0 +1,13 @@
> +What: /sys/fs/unicode/latest
> +Date: April 2020
> +Contact: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> +Description:
> + The latest version of the Unicode Standard supported by
> + this kernel
> +
Missing stop at the end of the sentence?
> +What: /sys/fs/unicode/encodings
> +Date: April 2020
> +Contact: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> +Description:
> + List of encodings and corresponding versions supported
> + by this kernel
Ditto.
> diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
> index 2a878b739115..b48e13e823a5 100644
> --- a/fs/unicode/utf8-core.c
> +++ b/fs/unicode/utf8-core.c
> @@ -6,6 +6,7 @@
> #include <linux/parser.h>
> #include <linux/errno.h>
> #include <linux/unicode.h>
> +#include <linux/fs.h>
>
> #include "utf8n.h"
>
> @@ -212,4 +213,67 @@ void utf8_unload(struct unicode_map *um)
> }
> EXPORT_SYMBOL(utf8_unload);
>
> +static ssize_t latest_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + int l = utf8version_latest();
> +
> + return snprintf(buf, PAGE_SIZE, "UTF-8 %d.%d.%d\n", UNICODE_AGE_MAJ(l),
> + UNICODE_AGE_MIN(l), UNICODE_AGE_REV(l));
> +
> +}
> +static ssize_t encodings_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + int n;
> +
> + n = snprintf(buf, PAGE_SIZE, "UTF-8:");
> + n += utf8version_list(buf + n, PAGE_SIZE - n);
> + n += snprintf(buf+n, PAGE_SIZE-n, "\n");
> +
I was wondering how sysfs-compliant this was,
in terms of one value per attribute.
Although, we do seem to break this on a few cases.
> + return n;
> +}
> +
> +#define UCD_ATTR(x) \
> + static struct kobj_attribute x ## _attr = __ATTR_RO(x)
> +
> +UCD_ATTR(latest);
> +UCD_ATTR(encodings);
> +
> +static struct attribute *ucd_attrs[] = {
> + &latest_attr.attr,
> + &encodings_attr.attr,
> + NULL,
> +};
> +static const struct attribute_group ucd_attr_group = {
> + .attrs = ucd_attrs,
> +};
> +static struct kobject *ucd_root;
> +
> +static int __init ucd_init(void)
> +{
> + int ret;
> +
> + ucd_root = kobject_create_and_add("unicode", fs_kobj);
> + if (!ucd_root)
> + return -ENOMEM;
> +
> + ret = sysfs_create_group(ucd_root, &ucd_attr_group);
> + if (ret) {
> + kobject_put(ucd_root);
> + ucd_root = NULL;
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static void __exit ucd_exit(void)
> +{
> + kobject_put(ucd_root);
> +}
> +
> +module_init(ucd_init);
This code is not a module, so how about fs_initcall?
> +module_exit(ucd_exit)
> +
I can be wrong, but I see no way to remove it :-)
Thanks,
Ezequiel
