bcachefs: extent_entry_next_safe()

We need to be able to iterate over extent ptrs that may be corrupted in
order to print them - this fixes a bug where we'd pop an assert in
bch2_bkey_durability_safe().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/extents.h

@@ -43,6 +43,11 @@ enum bkey_invalid_flags;
 #define extent_entry_next(_entry)					\
 	((typeof(_entry)) ((void *) (_entry) + extent_entry_bytes(_entry)))
 
+#define extent_entry_next_safe(_entry, _end)				\
+	(likely(__extent_entry_type(_entry) < BCH_EXTENT_ENTRY_MAX)	\
+	 ? extent_entry_next(_entry)					\
+	 : _end)
+
 static inline unsigned
 __extent_entry_type(const union bch_extent_entry *e)
 {
@@ -280,7 +285,7 @@ static inline struct bkey_ptrs bch2_bkey_ptrs(struct bkey_s k)
 #define __bkey_extent_entry_for_each_from(_start, _end, _entry)		\
 	for ((_entry) = (_start);					\
 	     (_entry) < (_end);						\
-	     (_entry) = extent_entry_next(_entry))
+	     (_entry) = extent_entry_next_safe(_entry, _end))
 
 #define __bkey_ptr_next(_ptr, _end)					\
 ({									\
@@ -318,7 +323,7 @@ static inline struct bkey_ptrs bch2_bkey_ptrs(struct bkey_s k)
 	(_ptr).has_ec	= false;					\
 									\
 	__bkey_extent_entry_for_each_from(_entry, _end, _entry)		\
-		switch (extent_entry_type(_entry)) {			\
+		switch (__extent_entry_type(_entry)) {			\
 		case BCH_EXTENT_ENTRY_ptr:				\
 			(_ptr).ptr		= _entry->ptr;		\
 			goto out;					\
@@ -344,7 +349,7 @@ out:									\
 	for ((_ptr).crc = bch2_extent_crc_unpack(_k, NULL),		\
 	     (_entry) = _start;						\
 	     __bkey_ptr_next_decode(_k, _end, _ptr, _entry);		\
-	     (_entry) = extent_entry_next(_entry))
+	     (_entry) = extent_entry_next_safe(_entry, _end))
 
 #define bkey_for_each_ptr_decode(_k, _p, _ptr, _entry)			\
 	__bkey_for_each_ptr_decode(_k, (_p).start, (_p).end,		\