Re: [PATCH] ext4: fix loop in do_split()

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roel kluin wrote:
unsigned i >= 0 is always true

Signed-off-by: Roel Kluin <roel.kluin@xxxxxxxxx>
---
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 63adcb7..389cf60 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1198,7 +1198,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
 	/* Split the existing block in the middle, size-wise */
 	size = 0;
 	move = 0;
-	for (i = count-1; i >= 0; i--) {
+	for (i = count-1; i < count; i--) {
 		/* is more than half of this entry in 2nd half of the block? */
 		if (size + map[i].size/2 > blocksize/2)
 			break;

While this unsigned wrap method is technically valid, it certainly isn't obvious, and making code readable should be a goal as well as making it correct. After all, code which is hard to read is hard to understand, making it hard to maintain. I therefore suggest the simpler form:
	for (i = count; i--; ) {
which gives the same i values inside the loop, but does assume that the reader remembers that i is unsigned, and intuitively understand wraparound while passing zero.

--
Bill Davidsen <davidsen@xxxxxxx>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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