On Wed, Mar 06, 2013 at 10:17:11PM +0800, Zheng Liu wrote:
> + if (ext4_es_status(es1) ^ ext4_es_status(es2))
> return 0;
>
> - if (ext4_es_status(es1) != ext4_es_status(es2))
Did you have a reason why changed != to ^?
It's identical from a functional perspective, but it's less obvious to
future readers of the code what's going on. I tried checking to see
if GCC did any better optimizing the code, but it doesn't seem to make
any difference. I'm going to switch it back to !=....
> + /* we need to check delayed extent is without unwritten status */
> + if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
> + return 1;
I'm not sure why we need to check the unwritten status? Under what
circumstances would we have an extent marked as under delayed
allocation but also unwritten?
- Ted
This is how I've restructured this function for now mainly to make it
easier to understand;
static int ext4_es_can_be_merged(struct extent_status *es1,
struct extent_status *es2)
{
if (ext4_es_status(es1) != ext4_es_status(es2))
return 0;
if (((__u64) es1->es_len) + es2->es_len > 0xFFFFFFFFULL)
return 0;
if (((__u64) es1->es_lblk) + es1->es_len != es2->es_lblk)
return 0;
if ((ext4_es_is_written(es1) || ext4_es_is_unwritten(es1)) &&
(ext4_es_pblock(es1) + es1->es_len == ext4_es_pblock(es2)))
return 1;
if (ext4_es_is_hole(es1))
return 1;
/* we need to check delayed extent is without unwritten status */
if (ext4_es_is_delayed(es1) && !ext4_es_is_unwritten(es1))
return 1;
return 0;
}
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