On Thu, Jul 28, 2016 at 11:35:34AM -0700, Darrick J. Wong wrote: > Kirill A. Shutemov reports that the kernel doesn't try to cap dest_count > in any way, and uses the number to allocate kernel memory. This causes > high order allocation warnings in the kernel log if someone passes in a > big enough value. We should clamp the allocation at PAGE_SIZE to avoid > stressing the VM. > > The two existing users of the dedupe ioctl never send more than 120 > requests, so we can safely clamp dest_range at PAGE_SIZE, because with > 4k pages we can handle up to 127 dedupe candidates. Given the max > extent length of 16MB, we can end up doing 2GB of IO which is plenty. > > Reported-by: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> Reviewed-by: Mark Fasheh <mfasheh@xxxxxxx> -- Mark Fasheh -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
