On Wed, Aug 28, 2019 at 08:57:19AM +0530, Souptick Joarder wrote: > On Tue, Aug 27, 2019 at 9:19 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > On Tue, Aug 27, 2019 at 01:48:57AM +0530, Souptick Joarder wrote: > > > On Mon, Aug 26, 2019 at 5:50 PM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > > > > > On Mon, Aug 26, 2019 at 01:32:09AM +0530, Souptick Joarder wrote: > > > > > On Mon, Aug 26, 2019 at 1:13 AM Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > > > > > > > > > On Sun, Aug 25, 2019 at 11:37:27AM +0530, Souptick Joarder wrote: > > > > > > > First, length passed to mmap is checked explicitly against > > > > > > > PAGE_SIZE. > > > > > > > > > > > > > > Second, if vma->vm_pgoff is passed as non zero, it would return > > > > > > > error. It appears like driver is expecting vma->vm_pgoff to > > > > > > > be passed as 0 always. > > > > > > > > > > > > ? pg_off is not zero > > > > > > > > > > Sorry, I mean, driver has a check against non zero to return error -EOPNOTSUPP > > > > > which means in true scenario driver is expecting vma->vm_pgoff should be passed > > > > > as 0. > > > > > > > > get_index is masking vm_pgoff, it is not 0 > > > > > > Sorry, I missed this part. Further looking into code, > > > in mlx5_ib_mmap(), vma_vm_pgoff is used to get command and > > > inside mlx5_ib_mmap_clock_info_page() entire *dev->mdev->clock_info* > > > is mapped. > > > > > > Consider that, the below modification will only take care of vma length > > > error check inside vm_map_pages_zero() and an extra check for vma > > > length is not needed. > > > > What is the point of vm_map_pages_zero() Is there some reason we should > > prefer it for mapping a single page? > > vm_map_pages_zero() can be used to map single/ multiple pages both. > There were drivers previously which either check length and pg_off explicitly > or didn't check for incorrect value of length /pg_off passed to it at > all. Calling > vm_map_pages_zero() in those places were more appropriate as it has > internal check for both. > > Now considering this patch, avoiding an extra check for length > explicitly is the only > part which can be avoided if converted to use vm_map_pages_zero() > because pg_off > is used in different context ( to identify command). So yes, > improvement wise convert > to use vm_map_pages_zero() is not making much difference here. So let's drop it, please. Thanks
