On 01/22/2013 02:57 AM, Marcelo Tosatti wrote:
> On Mon, Jan 21, 2013 at 04:05:27PM +0800, Asias He wrote:
>> We can get all the pages in one time instead of calling
>> gup N times.
>>
>> Signed-off-by: Asias He <asias@xxxxxxxxxx>
>> ---
>> drivers/vhost/tcm_vhost.c | 33 ++++++++++++++++++++-------------
>> 1 file changed, 20 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
>> index ca35c16..59be442 100644
>> --- a/drivers/vhost/tcm_vhost.c
>> +++ b/drivers/vhost/tcm_vhost.c
>> @@ -430,37 +430,45 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
>> * Returns the number of scatterlist entries used or -errno on error.
>> */
>> static int vhost_scsi_map_to_sgl(struct scatterlist *sgl,
>> - unsigned int sgl_count, void __user *ptr, size_t len, int write)
>> + unsigned int sgl_count, struct iovec *iov, int write)
>> {
>> struct scatterlist *sg = sgl;
>> unsigned int npages = 0;
>> + void __user *ptr = iov->iov_base;
>> + size_t len = iov->iov_len;
>> int ret;
>> + unsigned int pages_nr, offset, nbytes;
>> + struct page **pages;
>> +
>> + pages_nr = iov_num_pages(iov);
>> + pages = kmalloc(pages_nr * sizeof(struct page *), GFP_ATOMIC);
>> + if (!pages)
>> + return -ENOMEM;
>> +
>> + ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);
>> + if (ret != pages_nr)
>> + goto err;
>
> 1. Why GFP_ATOMIC? get_user_pages_fast can sleep, so this path must not
> be atomic (if it is, should use __get_user_pages_fast).
>
> GFP_ATOMIC should be avoided.
>
> 2. Should drop reference to pages whose refcount has been increased,
> if ret > 0 && ret != pages_nr (see last phrase of get_user_pages_fast
> commentary).
Thanks Marcelo. V2 is on the way.
--
Asias
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