a4d5613c4d
When unused memory map is freed the preserved part of the memory map is extended to match pageblock boundaries because lots of core mm functionality relies on homogeneity of the memory map within pageblock boundaries. Since pfn_valid() is used to check whether there is a valid memory map entry for a PFN, make it return true also for PFNs that have memory map entries even if there is no actual memory populated there. Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com> Tested-by: Tony Lindgren <tony@atomide.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.