[Ocfs2-devel] [PATCH 1/4] ocfs2/trivial: Move 'wanted' into parens of ocfs2_resmap_resv_bits.
Tao Ma
tao.ma at oracle.com
Sat Aug 14 01:19:25 PDT 2010
Hi Mark,
On 08/14/2010 07:16 AM, Mark Fasheh wrote:
> Hi Tao,
>
> On Mon, Aug 02, 2010 at 11:02:12AM +0800, Tao Ma wrote:
>> The first time I read the function ocfs2_resmap_resv_bits, I consider
>> about what 'wanted' will be used and consider about the comments.
>> Then I find it is only used if the reservation is empty. ;)
>>
>> So we'd better move it to the parens so that it make the code more
>> readable, what's more, ocfs2_resmap_resv_bits is used so frequently
>> and we should save some cpus. The corresponding BUG_ON is also moved
>> into parens since it is only meaningful after we reinit the resv.
>>
>> Cc: Mark Fasheh<mfasheh at suse.com>
>> Signed-off-by: Tao Ma<tao.ma at oracle.com>
>> ---
>> fs/ocfs2/reservations.c | 26 ++++++++++++--------------
>> 1 files changed, 12 insertions(+), 14 deletions(-)
>>
>> diff --git a/fs/ocfs2/reservations.c b/fs/ocfs2/reservations.c
>> index d8b6e42..567c1a0 100644
>> --- a/fs/ocfs2/reservations.c
>> +++ b/fs/ocfs2/reservations.c
>> @@ -732,25 +732,23 @@ int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
>> struct ocfs2_alloc_reservation *resv,
>> int *cstart, int *clen)
>> {
>> - unsigned int wanted = *clen;
>> -
>> if (resv == NULL || ocfs2_resmap_disabled(resmap))
>> return -ENOSPC;
>>
>> spin_lock(&resv_lock);
>>
>> - /*
>> - * We don't want to over-allocate for temporary
>> - * windows. Otherwise, we run the risk of fragmenting the
>> - * allocation space.
>> - */
>> - wanted = ocfs2_resv_window_bits(resmap, resv);
>> - if ((resv->r_flags& OCFS2_RESV_FLAG_TMP) || wanted< *clen)
>> - wanted = *clen;
>> -
>> if (ocfs2_resv_empty(resv)) {
>> - mlog(0, "empty reservation, find new window\n");
>> + /*
>> + * We don't want to over-allocate for temporary
>> + * windows. Otherwise, we run the risk of fragmenting the
>> + * allocation space.
>> + */
>> + unsigned int wanted = ocfs2_resv_window_bits(resmap, resv);
>> +
>> + if ((resv->r_flags& OCFS2_RESV_FLAG_TMP) || wanted< *clen)
>> + wanted = *clen;
>>
>> + mlog(0, "empty reservation, find new window\n");
>> /*
>> * Try to get a window here. If it works, we must fall
>> * through and test the bitmap . This avoids some
>> @@ -759,9 +757,9 @@ int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
>> * that inode.
>> */
>> ocfs2_resv_find_window(resmap, resv, wanted);
>> - }
>>
>> - BUG_ON(ocfs2_resv_empty(resv));
>> + BUG_ON(ocfs2_resv_empty(resv));
>> + }
>
> Can we leave the BUG_ON() outside the if (ocfs2_resv_empty(...)) { } block?
> You're technically correct in that the only possibility right now is if
> there's a bug in ocfs2_resv_find_window(). However, I think it still belongs
> outside the block because we're returning an allocation at that point. The
> code is self documenting then - "don't let it get here unless resv->r_start
> and resv->r_len mean something". That way any future changes to the function
> will be forced to take this BUG_ON() into consideration, and we are then
> less likely to accidentally corrupt data.
Actually I have thought of it. But please note that the if check is
ocfs2_resv_empty. So does it look a little bit strange that:
if (ocfs2_resv_empty()) {
}
BUG_ON(ocfs2_resv_empty());
We have just checked ocfs2_resv_empty and now we BUG_ON it again?
Regards,
Tao
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