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SubjectRe: [patch] [SCSI] scsi_transport_sas: check for allocation failure
On 13-03-11 09:10 AM, Dan Carpenter wrote:
> On Fri, Mar 08, 2013 at 10:50:19PM +0000, James Bottomley wrote:
>> On Fri, 2013-03-08 at 12:57 -0500, Douglas Gilbert wrote:
>>> On 13-03-08 07:02 AM, Dan Carpenter wrote:
>>>> Static checkers complain that this allocation isn't checked. We
>>>> should return zero if the allocation fails.
>>>>
>>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>>
>>>> diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
>>>> index 1b68142..a022997 100644
>>>> --- a/drivers/scsi/scsi_transport_sas.c
>>>> +++ b/drivers/scsi/scsi_transport_sas.c
>>>> @@ -379,9 +379,12 @@ sas_tlr_supported(struct scsi_device *sdev)
>>>> {
>>>> const int vpd_len = 32;
>>>> struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
>>>> - char *buffer = kzalloc(vpd_len, GFP_KERNEL);
>>>> + char *buffer;
>>>> int ret = 0;
>>>>
>>>> + buffer = kzalloc(vpd_len, GFP_KERNEL);
>>>> + if (!buffer)
>>>> + goto out;
>>>> if (scsi_get_vpd_page(sdev, 0x90, buffer, vpd_len))
>>>> goto out;
>>>>
>>>
>>> For 32 bytes, why not use the stack?
>>
>> Because the buffer is a DMA target. You can't DMA to stack because of
>> padding and cacheline issues.
>>
>
> I think stack data works here. scsi_execute() calls
> blk_rq_map_kern() which handles stack memory and alignment issues.

That being the case, several other callers of
scsi_get_vpd_page() 9and friends) could be
simplified and sped up.

Also since VPD pages don't change and they can carry
a lot of disparate information (e.g. the Extended
Inquiry and Block Limits pages) perhaps they could
be cached by the appropriate level (e.g. Extended
Inquiry cached by mid-level; Block Limits cached
by sd driver).

Doug Gilbert




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