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Currently we assume userspace pages are always writable when doing memory pinning. This is not true, specially since userspace applications may allocate their memory the way they want, we have no control over it. If a read-only page is set for pinning, currently the driver fails due to get_user_pages_fast() refusing to map read-only pages as writable. This patch changes this behavior, by taking the permission flags of the pages into account in both pinning/unpinning process, as well as in the DMA data copy-back to userpace (which we shouldn't try to do blindly, since it will fail in case of read-only-pages). Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.