bcachefs: Fix bkey format calculation

For extents, we increase the number of bits of the size field to allow
extents to get bigger due to merging - but this code didn't check for
overflow.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/bkey.c b/fs/bcachefs/bkey.c
index d6960e259c804897137220f3f26ad734a087b35f..0a5bfe6e9a2da57ce9bc628941dc7833aca6d6e7 100644 (file)
--- a/fs/bcachefs/bkey.c
+++ b/fs/bcachefs/bkey.c
@@ -591,8 +591,10 @@ struct bkey_format bch2_bkey_format_done(struct bkey_format_state *s)
 
        /* allow for extent merging: */
        if (ret.bits_per_field[BKEY_FIELD_SIZE]) {
-               ret.bits_per_field[BKEY_FIELD_SIZE] += 4;
-               bits += 4;
+               unsigned b = min(4U, 32U - ret.bits_per_field[BKEY_FIELD_SIZE]);
+
+               ret.bits_per_field[BKEY_FIELD_SIZE] += b;
+               bits += b;
        }
 
        ret.key_u64s = DIV_ROUND_UP(bits, 64);