Re: [PATCH] 1/6 Avoid overflows in calculations of groups_count

Theodore Tso wrote:
> On Wed, Aug 16, 2006 at 03:50:02PM -0500, Eric Sandeen wrote:
>> When s_blocks_count is at its maximum value (2^32-1), the way
>> groups_count was calculated could overflow; change the arithmetic to
>> avoid this.
>>
>> This is the same calculation that was submitted for the ext3 kernel
>> mount code.
>>
>> Signed-off-by: Eric Sandeen <[email protected]>
>
>
> I created a new inline function, ext2fs_div_ceil(), which is used to
> replace the problematic calculations.  This makes it easier to audit
> the changes, and it turns out it is needed in a lot more places than
> just the groups_count calculation.  I've taken hopefully all of the
> other related fixups from your other patch and bundled them into this
> patchset which introduces the use of the div_ceil() function.
>
> 						- Ted

Looks good, Ted - and I think there's one more:

Index: e2fsprogs-1.39/resize/online.c
===================================================================
--- e2fsprogs-1.39.orig/resize/online.c
+++ e2fsprogs-1.39/resize/online.c
@@ -59,8 +59,7 @@ errcode_t online_resize_fs(ext2_filsys f
 		exit(1);
 	}
 
-	r_frac = ((100 * sb->s_r_blocks_count) + sb->s_blocks_count-1) /
-		sb->s_blocks_count;
+	r_frac = ext2fs_div_ceil(100 * sb->s_r_blocks_count, sb->s_blocks_count);
 
 	retval = ext2fs_read_bitmaps(fs);
 	if (retval)

-Eric


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