[PATCH v2] zfs: recognize zpools formatted with features support

[WHR]

Currently no features are implemented, only the zpool version 5000 that
indicating the features support, is recognized. Since it is possible for
OpenZFS to create a pool with features support enabled, but without
enabling any actual feature, this change enables U-Boot to read such
pools.

Signed-off-by: WHR <msl0000023...@gmail.com>

---
v2:
Remove an unused local variable definition.

diff --git a/fs/zfs/zfs.c b/fs/zfs/zfs.c
index 4896cc18ef..113b428a93 100644
--- a/fs/zfs/zfs.c
+++ b/fs/zfs/zfs.c
@@ -336,6 +336,12 @@ vdev_uberblock_compare(uberblock_t *ub1, uberblock_t *ub2)
        return 0;
 }
 
+static inline int
+is_supported_spa_version(uint64_t version) {
+       return version == FEATURES_SUPPORTED_SPA_VERSION ||
+               (version > 0 && version <= SPA_VERSION);
+}
+
 /*
  * Three pieces of information are needed to verify an uberblock: the magic
  * number, the version number, and the checksum.
@@ -357,14 +363,12 @@ uberblock_verify(uberblock_t *uber, int offset, struct 
zfs_data *data)
                return ZFS_ERR_BAD_FS;
        }
 
-       if (zfs_to_cpu64(uber->ub_magic, LITTLE_ENDIAN) == UBERBLOCK_MAGIC
-               && zfs_to_cpu64(uber->ub_version, LITTLE_ENDIAN) > 0
-               && zfs_to_cpu64(uber->ub_version, LITTLE_ENDIAN) <= SPA_VERSION)
+       if (zfs_to_cpu64(uber->ub_magic, LITTLE_ENDIAN) == UBERBLOCK_MAGIC &&
+               is_supported_spa_version(zfs_to_cpu64(uber->ub_version, 
LITTLE_ENDIAN)))
                endian = LITTLE_ENDIAN;
 
-       if (zfs_to_cpu64(uber->ub_magic, BIG_ENDIAN) == UBERBLOCK_MAGIC
-               && zfs_to_cpu64(uber->ub_version, BIG_ENDIAN) > 0
-               && zfs_to_cpu64(uber->ub_version, BIG_ENDIAN) <= SPA_VERSION)
+       if (zfs_to_cpu64(uber->ub_magic, BIG_ENDIAN) == UBERBLOCK_MAGIC &&
+               is_supported_spa_version(zfs_to_cpu64(uber->ub_version, 
BIG_ENDIAN)))
                endian = BIG_ENDIAN;
 
        if (endian == UNKNOWN_ENDIAN) {
@@ -1790,7 +1794,7 @@ check_pool_label(struct zfs_data *data)
                return ZFS_ERR_BAD_FS;
        }
 
-       if (version > SPA_VERSION) {
+       if (!is_supported_spa_version(version)) {
                free(nvlist);
                printf("SPA version too new %llu > %llu\n",
                           (unsigned long long) version,
diff --git a/include/zfs/zfs.h b/include/zfs/zfs.h
index 17b93c10c8..72d87452dd 100644
--- a/include/zfs/zfs.h
+++ b/include/zfs/zfs.h
@@ -15,6 +15,7 @@
  * On-disk version number.
  */
 #define        SPA_VERSION                     28ULL
+#define        FEATURES_SUPPORTED_SPA_VERSION  5000ULL
 
 /*
  * The following are configuration names used in the nvlist describing a pool's