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Message-ID: <4931E024.2010500@tmr.com>
Date: Sat, 29 Nov 2008 19:36:52 -0500
From: Bill Davidsen <davidsen@....com>
To: roel kluin <roel.kluin@...il.com>
CC: tytso@....edu, adilger@....com, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: fix loop in do_split()
roel kluin wrote:
> unsigned i >= 0 is always true
>
> Signed-off-by: Roel Kluin <roel.kluin@...il.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@....com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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