Fix stack inline

Decrease stack usage for various call paths by forcing certain
functions to be inlined.  By inlining the functions the overhead
of a new stack frame is removed at the cost of increased code size.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

module/zfs/dbuf.c

@@ -1607,7 +1607,8 @@ dbuf_clear(dmu_buf_impl_t *db)
 		dbuf_rele(parent, db);
 }
 
-static int
+__attribute__((always_inline))
+static inline int
 dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
     dmu_buf_impl_t **parentp, blkptr_t **bpp, struct dbuf_hold_impl_data *dh)
 {