6426aaa60c
commit 07464e88365e9236febaca9ed1a2e2006d8bc952 upstream. Libnvdimm reserves the first 8K of pfn and devicedax namespaces to store a superblock describing the namespace. This 8K reservation is contained within the altmap area which the kernel uses for the vmemmap backing for the pages within the namespace. The altmap allows for some pages at the start of the altmap area to be reserved and that mechanism is used to protect the superblock from being re-used as vmemmap backing. The number of PFNs to reserve is calculated using: PHYS_PFN(SZ_8K) Which is implemented as: #define PHYS_PFN(x) ((unsigned long)((x) >> PAGE_SHIFT)) So on systems where PAGE_SIZE is greater than 8K the reservation size is truncated to zero and the superblock area is re-used as vmemmap backing. As a result all the namespace information stored in the superblock (i.e. if it's a PFN or DAX namespace) is lost and the namespace needs to be re-created to get access to the contents. This patch fixes this by using PFN_UP() rather than PHYS_PFN() to ensure that at least one page is reserved. On systems with a 4K pages size this patch should have no effect. Cc: stable@vger.kernel.org Cc: Dan Williams <dan.j.williams@intel.com> Fixes: ac515c084be9 ("libnvdimm, pmem, pfn: move pfn setup to the core") Signed-off-by: Oliver O'Halloran <oohall@gmail.com> Reviewed-by: Vishal Verma <vishal.l.verma@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.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.