zfs_prop_inherit() refreshes the stored values for native props, but not for user ones

[nabijaczleweli]

System information

Type	Version/Name
Distribution Name	Debian
Distribution Version	sid (2020-10-14)
Linux Kernel	5.8.0-2-686-pae
Architecture	i686
ZFS Version	0.8.4-2
SPL Version	0.8.4-2

(I realise this is a vaguely out-of-date version, but the code on the master branch is identical to the one under the zfs-0.8.4 tag so I'm reporting anyway.

Describe the problem you're observing

Calling zfs_prop_inherit() to, e.g., remove a user property doesn't make it go away from the cache in the handle.

Describe how to reproduce the problem

nvlist_t * data = zfs_get_user_props(dataset);
dump_nvlist(data, 2);
printf("\n");
zfs_prop_inherit(dataset, "xyz.nabijaczleweli:tzpfms-data", B_FALSE);
dump_nvlist(zfs_get_user_props(dataset), 2);
zfs_refresh_properties(dataset);
printf("\n");
dump_nvlist(zfs_get_user_props(dataset), 2);

prints

  xyz.nabijaczleweli:tzpfms-data:
      value: 'E2ACF7893237CB9467EB2BE9A3488372D54CC51C9965B08D05A6D5FF7AF7EBFC'
      source: 'owo/enc'

  xyz.nabijaczleweli:tzpfms-data:
      value: 'E2ACF7893237CB9467EB2BE9A3488372D54CC51C9965B08D05A6D5FF7AF7EBFC'
      source: 'owo/enc'

and likewise for zfs_get_all_props(), but I'll spare the volumous output.

The user prop fastpath just returns after the ioctl():

		if (zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_INHERIT_PROP, &zc) != 0)
			return (zfs_standard_error(hdl, errno, errbuf));

		return (0);

but the native prop path synchronises the properties as well:

	if ((ret = zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_INHERIT_PROP, &zc)) != 0) {
		return (zfs_standard_error(hdl, errno, errbuf));
	} else {

		if ((ret = changelist_postfix(cl)) != 0)
			goto error;

		/*
		 * Refresh the statistics so the new property is reflected.
		 */
		(void) get_stats(zhp);

As seen above, calling zfs_refresh_properties(), which is a trivial wrapper around get_stats(), fixes this.

[nabijaczleweli]

A test-case that actually functions:

int main(int argc, char **argv) {
	void *zhp = libzfs_init();
	void *dataset = zfs_open(zhp, "zest/__test", 1);

	printf("before:");
	dump_nvlist(zfs_get_user_props(dataset), 2);
	printf("\n");

	zfs_prop_inherit(dataset, "xyz.nabijaczleweli:test", 0);
	printf("after:");
	dump_nvlist(zfs_get_user_props(dataset), 2);
	printf("\n");

	zfs_refresh_properties(dataset);
	printf("refreshed:");
	dump_nvlist(zfs_get_user_props(dataset), 2);
	printf("\n");
}

with

$ cc a.c  libzfs/.libs/libzfs.so libnvpair/.libs/libnvpair.so
# zfs set xyz.nabijaczleweli:test=hehe zest/__test
# ./a.out
before:  xyz.nabijaczleweli:test:
      value: 'hehe'
      source: 'zest/__test'

after:  xyz.nabijaczleweli:test:
      value: 'hehe'
      source: 'zest/__test'

refreshed: