bcachefs: Fix undefined behaviour in eytzinger1_first()

Kent Overstreet · Kent Overstreet · commit 8ed58789fc43 · 2024-07-10T09:53:39.000-04:00
Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
diff --git a/fs/bcachefs/eytzinger.h b/fs/bcachefs/eytzinger.h
@@ -48,7 +48,7 @@ static inline unsigned eytzinger1_right_child(unsigned i)
 
 static inline unsigned eytzinger1_first(unsigned size)
 {
-	return rounddown_pow_of_two(size);
+	return size ? rounddown_pow_of_two(size) : 0;
 }
 
 static inline unsigned eytzinger1_last(unsigned size)
@@ -101,7 +101,9 @@ static inline unsigned eytzinger1_prev(unsigned i, unsigned size)
 
 static inline unsigned eytzinger1_extra(unsigned size)
 {
-	return (size + 1 - rounddown_pow_of_two(size)) << 1;
+	return size
+		? (size + 1 - rounddown_pow_of_two(size)) << 1
+		: 0;
 }
 
 static inline unsigned __eytzinger1_to_inorder(unsigned i, unsigned size,

Original file line number	Diff line number	Diff line change
`@@ -48,7 +48,7 @@ static inline unsigned eytzinger1_right_child(unsigned i)`
`48`	`48`
`49`	`49`	`static inline unsigned eytzinger1_first(unsigned size)`
`50`	`50`	`{`
`51`		`- return rounddown_pow_of_two(size);`
	`51`	`+ return size ? rounddown_pow_of_two(size) : 0;`
`52`	`52`	`}`
`53`	`53`
`54`	`54`	`static inline unsigned eytzinger1_last(unsigned size)`
`@@ -101,7 +101,9 @@ static inline unsigned eytzinger1_prev(unsigned i, unsigned size)`
`101`	`101`
`102`	`102`	`static inline unsigned eytzinger1_extra(unsigned size)`
`103`	`103`	`{`
`104`		`- return (size + 1 - rounddown_pow_of_two(size)) << 1;`
	`104`	`+ return size`
	`105`	`+ ? (size + 1 - rounddown_pow_of_two(size)) << 1`
	`106`	`+ : 0;`
`105`	`107`	`}`
`106`	`108`
`107`	`109`	`static inline unsigned __eytzinger1_to_inorder(unsigned i, unsigned size,`