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ext2/ext3:useless code for return value

PATCH In review 潘卫平(Peter Pan) 2 participants 3 messages May 6, 2010 – May 10, 2010

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#0 lore raw

PATCH 1/1 ext2/ext3:useless code for return value

When rsv is the right hand side of goal, we should return NULL, because now rsv's prev is NULL, or we return rsv.

---
 fs/ext2/balloc.c |    6 +-----
 fs/ext3/balloc.c |    6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)
fs/ext2/balloc.c +0 -0
index 3cf038c..023990f 100644
@@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,

ext2_fsblk_t goal)
* side of the interval containing the goal. If it's the RHS,
* we need to back up one.
*/
- if (rsv->rsv_start > goal) {
- n = rb_prev(&rsv->rsv_node);
- rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
- }
- return rsv;
+ return (rsv->rsv_start < goal) ? rsv : NULL;
}

/*

fs/ext3/balloc.c +0 -0
index a177122..bfa62e9 100644
@@ -310,11 +310,7 @@ search_reserve_window(struct rb_root *root,

ext3_fsblk_t goal)
* side of the interval containing the goal. If it's the RHS,
* we need to back up one.
*/
- if (rsv->rsv_start > goal) {
- n = rb_prev(&rsv->rsv_node);
- rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
- }
- return rsv;
+ return (rsv->rsv_start < goal) ? rsv : NULL;
}

/**

Signature · 10 lines
1.6.6


-- 
Peter Pan(潘卫平)
Red Flag Software Co.,Ltd
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#1 lore raw
Quoted 15 lines

When rsv is the right hand side of goal, we should return NULL, because now rsv's prev is NULL, or we return rsv.

---
 fs/ext2/balloc.c |    6 +-----
 fs/ext3/balloc.c |    6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)
fs/ext2/balloc.c +0 -0
index 3cf038c..023990f 100644

fs/ext2/balloc.c search_reserve_window(struct rb_root *root, · line 327

Quoted 10 lines
fs/ext2/balloc.c +1 -5
@@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,
 ext2_fsblk_t goal)
 	 * side of the interval containing the goal.  If it's the RHS,
 	 * we need to back up one.
 	 */
-	if (rsv->rsv_start > goal) {
-		n = rb_prev(&rsv->rsv_node);
-		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
-	}
-	return rsv;
+    return (rsv->rsv_start < goal) ? rsv : NULL;

Hmm, I'm not sure I understand your reasoning. Suppose we have an RB-tree
with two intervals 0-10, 20-30. Interval 0-10 is in the root. Now we search for goal 15. In the root we go to right because 10<15, in the next node we go to left because 15 < 20. Then the loop terminates. Now your code would return NULL but previous code would return rb_prev of interval 20-30 which is 0-10. And that is what we want as far as I understand what we expect from the function...

Honza

Signature · 6 lines
Jan Kara <[email protected]>
SuSE CR Labs
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#2 lore raw
Quoted 33 lines · Jan Kara
Quoted 15 lines

When rsv is the right hand side of goal, we should return NULL, because now rsv's prev is NULL, or we return rsv.

---
  fs/ext2/balloc.c |    6 +-----
  fs/ext3/balloc.c |    6 +-----
  2 files changed, 2 insertions(+), 10 deletions(-)
fs/ext2/balloc.c +0 -0
index 3cf038c..023990f 100644

fs/ext2/balloc.c search_reserve_window(struct rb_root *root, · line 327

Quoted 10 lines
fs/ext2/balloc.c +1 -5
@@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,
 ext2_fsblk_t goal)
  	 * side of the interval containing the goal.  If it's the RHS,
  	 * we need to back up one.
  	 */
-	if (rsv->rsv_start>  goal) {
-		n = rb_prev(&rsv->rsv_node);
-		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
-	}
-	return rsv;
+    return (rsv->rsv_start<  goal) ? rsv : NULL;

Hmm, I'm not sure I understand your reasoning. Suppose we have an RB-tree
with two intervals 0-10, 20-30. Interval 0-10 is in the root. Now we search for goal 15. In the root we go to right because 10<15, in the next node we go to left because 15< 20. Then the loop terminates. Now your code would return NULL but previous code would return rb_prev of interval 20-30 which is 0-10. And that is what we want as far as I understand what we expect from the function...

Quoted 1 line

Honza

You got the point!
Many thanks.

Regards

Signature · 2 lines
Peter Pan
Red Flag Software Co.,Ltd