On Thu, Apr 17, 2008 at 06:09:14PM +0200, Roel Kluin wrote:
> ext4_mb_init_backend() has a variable i of type ext4_group_t. which is typedefined
> in include/linux/ext4_fs_i.h:34 to unsigned long. Since unsigned, i >= 0 is always
> true, so fix hot spins after err_freebuddy and err_freemeta.
>
> Signed-off-by: Roel Kluin <12o3l@xxxxxxxxxx>
> ---
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index ef97f19..afba9b8 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2618,14 +2618,14 @@ static int ext4_mb_init_backend(struct super_block *sb)
> return 0;
The function needs more changes. For ex:
2279 if (meta_group_info[j] == NULL) {
2280 printk(KERN_ERR "EXT4-fs: can't allocate buddy mem\n");
2281 i--;
2282 goto err_freebuddy;
2283 }
That decrement i--; could result in bad value if i == 0;.
>
> err_freebuddy:
> - while (i >= 0) {
> + do {
> kfree(ext4_get_group_info(sb, i));
> - i--;
> - }
> - i = num_meta_group_infos;
> + } while (i-- != 0);
> + i = num_meta_group_infos - 1;
> err_freemeta:
> - while (--i >= 0)
> + do {
> kfree(sbi->s_group_info[i]);
> + } while (i-- != 0);
> iput(sbi->s_buddy_cache);
> err_freesgi:
> kfree(sbi->s_group_info);
-aneesh
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