[PATCH] ext4: fix loop in do_split()

[PATCH] ext4: fix loop in do_split()

[roel kluin]

unsigned i >= 0 is always true

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
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;

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

[Bill Davidsen]

roel kluin wrote:
> unsigned i >= 0 is always true
> 
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
> ---
> 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@tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot