• David Hildenbrand's avatar
    fs/proc/page.c: allow inspection of last section and fix end detection · abec749f
    David Hildenbrand authored
    If max_pfn does not fall onto a section boundary, it is possible to
    inspect PFNs up to max_pfn, and PFNs above max_pfn, however, max_pfn
    itself can't be inspected.  We can have a valid (and online) memmap at and
    above max_pfn if max_pfn is not aligned to a section boundary.  The whole
    early section has a memmap and is marked online.  Being able to inspect
    the state of these PFNs is valuable for debugging, especially because
    max_pfn can change on memory hotplug and expose these memmaps.
    
    Also, querying page flags via "./page-types -r -a 0x144001,"
    (tools/vm/page-types.c) inside a x86-64 guest with 4160MB under QEMU
    results in an (almost) endless loop in user space, because the end is not
    detected properly when starting after max_pfn.
    
    Instead, let's allow to inspect all pages in the highest section and
    return 0 directly if we try to access pages above that section.
    
    While at it, check the count before adjusting it, to avoid masking user
    errors.
    
    Link: http://lkml.kernel.org/r/20191211163201.17179-3-david@redhat.comSigned-off-by: default avatarDavid Hildenbrand <david@redhat.com>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: Oscar Salvador <osalvador@suse.de>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Bob Picco <bob.picco@oracle.com>
    Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
    Cc: Steven Sistare <steven.sistare@oracle.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    abec749f
page.c 7.91 KB