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 <[email protected]> > --- > 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). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
