bcachefs: Better incompat version/feature error messages

If we can't mount because of an incompatibility, print what's supported
and unsupported - to help solve PEBKAC issues.

Reported-by: Roland Vet <vet.roland@protonmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index f87e3bf33ec0c50c0066cf1d8d5deb3be3969c19..7dcabc9676f4f81ace45bab871b8817fab622349 100644 (file)
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -377,15 +377,27 @@ static int bch2_sb_validate(struct bch_sb_handle *disk_sb,
        if (ret)
                return ret;
 
-       if (sb->features[1] ||
-           (le64_to_cpu(sb->features[0]) & (~0ULL << BCH_FEATURE_NR))) {
-               prt_printf(out, "Filesystem has incompatible features");
+       u64 incompat = le64_to_cpu(sb->features[0]) & (~0ULL << BCH_FEATURE_NR);
+       unsigned incompat_bit = 0;
+       if (incompat)
+               incompat_bit = __ffs64(incompat);
+       else if (sb->features[1])
+               incompat_bit = 64 + __ffs64(le64_to_cpu(sb->features[1]));
+
+       if (incompat_bit) {
+               prt_printf(out, "Filesystem has incompatible feature bit %u, highest supported %s (%u)",
+                          incompat_bit,
+                          bch2_sb_features[BCH_FEATURE_NR - 1],
+                          BCH_FEATURE_NR - 1);
                return -BCH_ERR_invalid_sb_features;
        }
 
        if (BCH_VERSION_MAJOR(le16_to_cpu(sb->version)) > BCH_VERSION_MAJOR(bcachefs_metadata_version_current) ||
            BCH_SB_VERSION_INCOMPAT(sb) > bcachefs_metadata_version_current) {
-               prt_printf(out, "Filesystem has incompatible version");
+               prt_str(out, "Filesystem has incompatible version ");
+               bch2_version_to_text(out, le16_to_cpu(sb->version));
+               prt_str(out, ", current version ");
+               bch2_version_to_text(out, bcachefs_metadata_version_current);
                return -BCH_ERR_invalid_sb_features;
        }