1. 14 May, 2014 3 commits
    • Helge Deller's avatar
      parisc,metag: Do not hardcode maximum userspace stack size · 042d27ac
      Helge Deller authored
      This patch affects only architectures where the stack grows upwards
      (currently parisc and metag only). On those do not hardcode the maximum
      initial stack size to 1GB for 32-bit processes, but make it configurable
      via a config option.
      
      The main problem with the hardcoded stack size is, that we have two
      memory regions which grow upwards: stack and heap. To keep most of the
      memory available for heap in a flexmap memory layout, it makes no sense
      to hard allocate up to 1GB of the memory for stack which can't be used
      as heap then.
      
      This patch makes the stack size for 32-bit processes configurable and
      uses 80MB as default value which has been in use during the last few
      years on parisc and which hasn't showed any problems yet.
      Signed-off-by: default avatarHelge Deller <deller@gmx.de>
      Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
      Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
      Cc: linux-parisc@vger.kernel.org
      Cc: linux-metag@vger.kernel.org
      Cc: John David Anglin <dave.anglin@bell.net>
      042d27ac
    • James Hogan's avatar
      metag: Reduce maximum stack size to 256MB · d71f290b
      James Hogan authored
      Specify the maximum stack size for arches where the stack grows upward
      (parisc and metag) in asm/processor.h rather than hard coding in
      fs/exec.c so that metag can specify a smaller value of 256MB rather than
      1GB.
      
      This fixes a BUG on metag if the RLIMIT_STACK hard limit is increased
      beyond a safe value by root. E.g. when starting a process after running
      "ulimit -H -s unlimited" it will then attempt to use a stack size of the
      maximum 1GB which is far too big for metag's limited user virtual
      address space (stack_top is usually 0x3ffff000):
      
      BUG: failure at fs/exec.c:589/shift_arg_pages()!
      Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
      Cc: Helge Deller <deller@gmx.de>
      Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
      Cc: linux-parisc@vger.kernel.org
      Cc: linux-metag@vger.kernel.org
      Cc: John David Anglin <dave.anglin@bell.net>
      Cc: stable@vger.kernel.org # only needed for >= v3.9 (arch/metag)
      d71f290b
    • Mikulas Patocka's avatar
      metag: fix memory barriers · 2425ce84
      Mikulas Patocka authored
      Volatile access doesn't really imply the compiler barrier. Volatile access
      is only ordered with respect to other volatile accesses, it isn't ordered
      with respect to general memory accesses. Gcc may reorder memory accesses
      around volatile access, as we can see in this simple example (if we
      compile it with optimization, both increments of *b will be collapsed to
      just one):
      
      void fn(volatile int *a, long *b)
      {
      	(*b)++;
      	*a = 10;
      	(*b)++;
      }
      
      Consequently, we need the compiler barrier after a write to the volatile
      variable, to make sure that the compiler doesn't reorder the volatile
      write with something else.
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Cc: stable@vger.kernel.org
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
      2425ce84
  2. 09 May, 2014 6 commits
  3. 08 May, 2014 9 commits
  4. 07 May, 2014 6 commits
  5. 06 May, 2014 16 commits
    • Dave Airlie's avatar
      Merge branch 'mullins' of git://people.freedesktop.org/~deathsimple/linux into drm-fixes · 995c376e
      Dave Airlie authored
      Add Mullins chips support.
      
      * 'mullins' of git://people.freedesktop.org/~deathsimple/linux:
        drm/radeon: add pci ids for Mullins
        drm/radeon: add Mullins VCE support
        drm/radeon: modesetting updates for Mullins.
        drm/radeon: dpm updates for KV/KB
        drm/radeon: add Mullins dpm support.
        drm/radeon: add Mullins UVD support.
        drm/radeon: update cik init for Mullins.
        drm/radeon: add Mullins chip family
      995c376e
    • Dave Airlie's avatar
      Merge branch 'drm-nouveau-next' of... · 2a1235e5
      Dave Airlie authored
      Merge branch 'drm-nouveau-next' of git://anongit.freedesktop.org/git/nouveau/linux-2.6 into drm-fixes
      
      nouveau fixes.
      
      * 'drm-nouveau-next' of git://anongit.freedesktop.org/git/nouveau/linux-2.6:
        drm/gm107/gr: bump attrib cb size quite a bit
        drm/nouveau: fix another lock unbalance in nouveau_crtc_page_flip
        drm/nouveau/bios: fix shadowing from PROM on big-endian systems
        drm/nouveau/acpi: allow non-optimus setups to load vbios from acpi
      2a1235e5
    • Dave Airlie's avatar
      Merge tag 'topc/core-stuff-2014-05-05' of git://anongit.freedesktop.org/drm-intel into drm-fixes · 508200c5
      Dave Airlie authored
      Some more i915 fixes. There's still some DP issues we are looking into,
      but wanted to get these moving.
      
      * tag 'topc/core-stuff-2014-05-05' of git://anongit.freedesktop.org/drm-intel:
        drm/i915: don't try DP_LINK_BW_5_4 on HSW ULX
        drm/i915: Sanitize the enable_ppgtt module option once
        drm/i915: Break encoder->crtc link separately in intel_sanitize_crtc()
      508200c5
    • Dave Airlie's avatar
      Merge branch 'drm-fixes-3.15' of git://people.freedesktop.org/~deathsimple/linux into drm-fixes · 9eabb911
      Dave Airlie authored
      this is the next pull quested for stashed up radeon fixes for 3.15. As discussed support for Mullins was separated out and will get it's own pull request. Remaining highlights are:
      1. Some more patches to better handle PLL limits.
      2. Making use of the PFLIP additional to the VBLANK interrupt, otherwise we sometimes miss page flip events.
      3. Fix for the UVD command stream parser.
      4. Fix for bootup UVD clocks on RV7xx systems.
      5. Adding missing error check on dpcd reads.
      6. Fixes number of banks calculation on SI.
      
      * 'drm-fixes-3.15' of git://people.freedesktop.org/~deathsimple/linux:
        drm/radeon: lower the ref * post PLL maximum
        drm/radeon: check that we have a clock before PLL setup
        drm/radeon: drm/radeon: add missing radeon_semaphore_free to error path
        drm/radeon: Fix num_banks calculation for SI
        drm/radeon/dp: check for errors in dpcd reads
        drm/radeon: avoid high jitter with small frac divs
        drm/radeon: check buffer relocation offset
        drm/radeon: use pflip irq on R600+ v2
        drm/radeon/uvd: use lower clocks on old UVD to boot v2
      9eabb911
    • Linus Torvalds's avatar
      Merge branch 'akpm' (incoming from Andrew) · 38583f09
      Linus Torvalds authored
      Merge misc fixes from Andrew Morton:
       "13 fixes"
      
      * emailed patches from Andrew Morton <akpm@linux-foundation.org>:
        agp: info leak in agpioc_info_wrap()
        fs/affs/super.c: bugfix / double free
        fanotify: fix -EOVERFLOW with large files on 64-bit
        slub: use sysfs'es release mechanism for kmem_cache
        revert "mm: vmscan: do not swap anon pages just because free+file is low"
        autofs: fix lockref lookup
        mm: filemap: update find_get_pages_tag() to deal with shadow entries
        mm/compaction: make isolate_freepages start at pageblock boundary
        MAINTAINERS: zswap/zbud: change maintainer email address
        mm/page-writeback.c: fix divide by zero in pos_ratio_polynom
        hugetlb: ensure hugepage access is denied if hugepages are not supported
        slub: fix memcg_propagate_slab_attrs
        drivers/rtc/rtc-pcf8523.c: fix month definition
      38583f09
    • Dan Carpenter's avatar
      agp: info leak in agpioc_info_wrap() · 3ca9e5d3
      Dan Carpenter authored
      On 64 bit systems the agp_info struct has a 4 byte hole between
      ->agp_mode and ->aper_base.  We need to clear it to avoid disclosing
      stack information to userspace.
      Signed-off-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
      Cc: David Airlie <airlied@linux.ie>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3ca9e5d3
    • Fabian Frederick's avatar
      fs/affs/super.c: bugfix / double free · d353efd0
      Fabian Frederick authored
      Commit 842a859d ("affs: use ->kill_sb() to simplify ->put_super()
      and failure exits of ->mount()") adds .kill_sb which frees sbi but
      doesn't remove sbi free in case of parse_options error causing double
      free+random crash.
      Signed-off-by: default avatarFabian Frederick <fabf@skynet.be>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: <stable@vger.kernel.org>	[3.14.x]
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d353efd0
    • Will Woods's avatar
      fanotify: fix -EOVERFLOW with large files on 64-bit · 1e2ee49f
      Will Woods authored
      On 64-bit systems, O_LARGEFILE is automatically added to flags inside
      the open() syscall (also openat(), blkdev_open(), etc).  Userspace
      therefore defines O_LARGEFILE to be 0 - you can use it, but it's a
      no-op.  Everything should be O_LARGEFILE by default.
      
      But: when fanotify does create_fd() it uses dentry_open(), which skips
      all that.  And userspace can't set O_LARGEFILE in fanotify_init()
      because it's defined to 0.  So if fanotify gets an event regarding a
      large file, the read() will just fail with -EOVERFLOW.
      
      This patch adds O_LARGEFILE to fanotify_init()'s event_f_flags on 64-bit
      systems, using the same test as open()/openat()/etc.
      
      Addresses https://bugzilla.redhat.com/show_bug.cgi?id=696821Signed-off-by: default avatarWill Woods <wwoods@redhat.com>
      Acked-by: default avatarEric Paris <eparis@redhat.com>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1e2ee49f
    • Christoph Lameter's avatar
      slub: use sysfs'es release mechanism for kmem_cache · 41a21285
      Christoph Lameter authored
      debugobjects warning during netfilter exit:
      
          ------------[ cut here ]------------
          WARNING: CPU: 6 PID: 4178 at lib/debugobjects.c:260 debug_print_object+0x8d/0xb0()
          ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x20
          Modules linked in:
          CPU: 6 PID: 4178 Comm: kworker/u16:2 Tainted: G        W 3.11.0-next-20130906-sasha #3984
          Workqueue: netns cleanup_net
          Call Trace:
            dump_stack+0x52/0x87
            warn_slowpath_common+0x8c/0xc0
            warn_slowpath_fmt+0x46/0x50
            debug_print_object+0x8d/0xb0
            __debug_check_no_obj_freed+0xa5/0x220
            debug_check_no_obj_freed+0x15/0x20
            kmem_cache_free+0x197/0x340
            kmem_cache_destroy+0x86/0xe0
            nf_conntrack_cleanup_net_list+0x131/0x170
            nf_conntrack_pernet_exit+0x5d/0x70
            ops_exit_list+0x5e/0x70
            cleanup_net+0xfb/0x1c0
            process_one_work+0x338/0x550
            worker_thread+0x215/0x350
            kthread+0xe7/0xf0
            ret_from_fork+0x7c/0xb0
      
      Also during dcookie cleanup:
      
          WARNING: CPU: 12 PID: 9725 at lib/debugobjects.c:260 debug_print_object+0x8c/0xb0()
          ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x20
          Modules linked in:
          CPU: 12 PID: 9725 Comm: trinity-c141 Not tainted 3.15.0-rc2-next-20140423-sasha-00018-gc4ff6c4 #408
          Call Trace:
            dump_stack (lib/dump_stack.c:52)
            warn_slowpath_common (kernel/panic.c:430)
            warn_slowpath_fmt (kernel/panic.c:445)
            debug_print_object (lib/debugobjects.c:262)
            __debug_check_no_obj_freed (lib/debugobjects.c:697)
            debug_check_no_obj_freed (lib/debugobjects.c:726)
            kmem_cache_free (mm/slub.c:2689 mm/slub.c:2717)
            kmem_cache_destroy (mm/slab_common.c:363)
            dcookie_unregister (fs/dcookies.c:302 fs/dcookies.c:343)
            event_buffer_release (arch/x86/oprofile/../../../drivers/oprofile/event_buffer.c:153)
            __fput (fs/file_table.c:217)
            ____fput (fs/file_table.c:253)
            task_work_run (kernel/task_work.c:125 (discriminator 1))
            do_notify_resume (include/linux/tracehook.h:196 arch/x86/kernel/signal.c:751)
            int_signal (arch/x86/kernel/entry_64.S:807)
      
      Sysfs has a release mechanism.  Use that to release the kmem_cache
      structure if CONFIG_SYSFS is enabled.
      
      Only slub is changed - slab currently only supports /proc/slabinfo and
      not /sys/kernel/slab/*.  We talked about adding that and someone was
      working on it.
      
      [akpm@linux-foundation.org: fix CONFIG_SYSFS=n build]
      [akpm@linux-foundation.org: fix CONFIG_SYSFS=n build even more]
      Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
      Reported-by: default avatarSasha Levin <sasha.levin@oracle.com>
      Tested-by: default avatarSasha Levin <sasha.levin@oracle.com>
      Acked-by: default avatarGreg KH <greg@kroah.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Cc: Bart Van Assche <bvanassche@acm.org>
      Cc: Al Viro <viro@ZenIV.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      41a21285
    • Johannes Weiner's avatar
      revert "mm: vmscan: do not swap anon pages just because free+file is low" · 62376251
      Johannes Weiner authored
      This reverts commit 0bf1457f ("mm: vmscan: do not swap anon pages
      just because free+file is low") because it introduced a regression in
      mostly-anonymous workloads, where reclaim would become ineffective and
      trap every allocating task in direct reclaim.
      
      The problem is that there is a runaway feedback loop in the scan balance
      between file and anon, where the balance tips heavily towards a tiny
      thrashing file LRU and anonymous pages are no longer being looked at.
      The commit in question removed the safe guard that would detect such
      situations and respond with forced anonymous reclaim.
      
      This commit was part of a series to fix premature swapping in loads with
      relatively little cache, and while it made a small difference, the cure
      is obviously worse than the disease.  Revert it.
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
      Acked-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
      Acked-by: default avatarRafael Aquini <aquini@redhat.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: <stable@kernel.org>		[3.12+]
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      62376251
    • Ian Kent's avatar
      autofs: fix lockref lookup · 6b6751f7
      Ian Kent authored
      autofs needs to be able to see private data dentry flags for its dentrys
      that are being created but not yet hashed and for its dentrys that have
      been rmdir()ed but not yet freed.  It needs to do this so it can block
      processes in these states until a status has been returned to indicate
      the given operation is complete.
      
      It does this by keeping two lists, active and expring, of dentrys in
      this state and uses ->d_release() to keep them stable while it checks
      the reference count to determine if they should be used.
      
      But with the recent lockref changes dentrys being freed sometimes don't
      transition to a reference count of 0 before being freed so autofs can
      occassionally use a dentry that is invalid which can lead to a panic.
      Signed-off-by: default avatarIan Kent <raven@themaw.net>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      6b6751f7
    • Johannes Weiner's avatar
      mm: filemap: update find_get_pages_tag() to deal with shadow entries · 139b6a6f
      Johannes Weiner authored
      Dave Jones reports the following crash when find_get_pages_tag() runs
      into an exceptional entry:
      
        kernel BUG at mm/filemap.c:1347!
        RIP: find_get_pages_tag+0x1cb/0x220
        Call Trace:
          find_get_pages_tag+0x36/0x220
          pagevec_lookup_tag+0x21/0x30
          filemap_fdatawait_range+0xbe/0x1e0
          filemap_fdatawait+0x27/0x30
          sync_inodes_sb+0x204/0x2a0
          sync_inodes_one_sb+0x19/0x20
          iterate_supers+0xb2/0x110
          sys_sync+0x44/0xb0
          ia32_do_call+0x13/0x13
      
        1343                         /*
        1344                          * This function is never used on a shmem/tmpfs
        1345                          * mapping, so a swap entry won't be found here.
        1346                          */
        1347                         BUG();
      
      After commit 0cd6144a ("mm + fs: prepare for non-page entries in
      page cache radix trees") this comment and BUG() are out of date because
      exceptional entries can now appear in all mappings - as shadows of
      recently evicted pages.
      
      However, as Hugh Dickins notes,
      
        "it is truly surprising for a PAGECACHE_TAG_WRITEBACK (and probably
         any other PAGECACHE_TAG_*) to appear on an exceptional entry.
      
         I expect it comes down to an occasional race in RCU lookup of the
         radix_tree: lacking absolute synchronization, we might sometimes
         catch an exceptional entry, with the tag which really belongs with
         the unexceptional entry which was there an instant before."
      
      And indeed, not only is the tree walk lockless, the tags are also read
      in chunks, one radix tree node at a time.  There is plenty of time for
      page reclaim to swoop in and replace a page that was already looked up
      as tagged with a shadow entry.
      
      Remove the BUG() and update the comment.  While reviewing all other
      lookup sites for whether they properly deal with shadow entries of
      evicted pages, update all the comments and fix memcg file charge moving
      to not miss shmem/tmpfs swapcache pages.
      
      Fixes: 0cd6144a ("mm + fs: prepare for non-page entries in page cache radix trees")
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Reported-by: default avatarDave Jones <davej@redhat.com>
      Acked-by: default avatarHugh Dickins <hughd@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      139b6a6f
    • Vlastimil Babka's avatar
      mm/compaction: make isolate_freepages start at pageblock boundary · 49e068f0
      Vlastimil Babka authored
      The compaction freepage scanner implementation in isolate_freepages()
      starts by taking the current cc->free_pfn value as the first pfn.  In a
      for loop, it scans from this first pfn to the end of the pageblock, and
      then subtracts pageblock_nr_pages from the first pfn to obtain the first
      pfn for the next for loop iteration.
      
      This means that when cc->free_pfn starts at offset X rather than being
      aligned on pageblock boundary, the scanner will start at offset X in all
      scanned pageblock, ignoring potentially many free pages.  Currently this
      can happen when
      
       a) zone's end pfn is not pageblock aligned, or
      
       b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE
          enabled and a hole spanning the beginning of a pageblock
      
      This patch fixes the problem by aligning the initial pfn in
      isolate_freepages() to pageblock boundary.  This also permits replacing
      the end-of-pageblock alignment within the for loop with a simple
      pageblock_nr_pages increment.
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Reported-by: default avatarHeesub Shin <heesub.shin@samsung.com>
      Acked-by: default avatarMinchan Kim <minchan@kernel.org>
      Cc: Mel Gorman <mgorman@suse.de>
      Acked-by: default avatarJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
      Cc: Michal Nazarewicz <mina86@mina86.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Christoph Lameter <cl@linux.com>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Dongjun Shin <d.j.shin@samsung.com>
      Cc: Sunghwan Yun <sunghwan.yun@samsung.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      49e068f0
    • Seth Jennings's avatar
      MAINTAINERS: zswap/zbud: change maintainer email address · 0e3b7e54
      Seth Jennings authored
      sjenning@linux.vnet.ibm.com is no longer a viable entity.
      Signed-off-by: default avatarSeth Jennings <sjennings@variantweb.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0e3b7e54
    • Rik van Riel's avatar
      mm/page-writeback.c: fix divide by zero in pos_ratio_polynom · d5c9fde3
      Rik van Riel authored
      It is possible for "limit - setpoint + 1" to equal zero, after getting
      truncated to a 32 bit variable, and resulting in a divide by zero error.
      
      Using the fully 64 bit divide functions avoids this problem.  It also
      will cause pos_ratio_polynom() to return the correct value when
      (setpoint - limit) exceeds 2^32.
      
      Also uninline pos_ratio_polynom, at Andrew's request.
      Signed-off-by: default avatarRik van Riel <riel@redhat.com>
      Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
      Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
      Cc: Luiz Capitulino <lcapitulino@redhat.com>
      Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d5c9fde3
    • Nishanth Aravamudan's avatar
      hugetlb: ensure hugepage access is denied if hugepages are not supported · 457c1b27
      Nishanth Aravamudan authored
      Currently, I am seeing the following when I `mount -t hugetlbfs /none
      /dev/hugetlbfs`, and then simply do a `ls /dev/hugetlbfs`.  I think it's
      related to the fact that hugetlbfs is properly not correctly setting
      itself up in this state?:
      
        Unable to handle kernel paging request for data at address 0x00000031
        Faulting instruction address: 0xc000000000245710
        Oops: Kernel access of bad area, sig: 11 [#1]
        SMP NR_CPUS=2048 NUMA pSeries
        ....
      
      In KVM guests on Power, in a guest not backed by hugepages, we see the
      following:
      
        AnonHugePages:         0 kB
        HugePages_Total:       0
        HugePages_Free:        0
        HugePages_Rsvd:        0
        HugePages_Surp:        0
        Hugepagesize:         64 kB
      
      HPAGE_SHIFT == 0 in this configuration, which indicates that hugepages
      are not supported at boot-time, but this is only checked in
      hugetlb_init().  Extract the check to a helper function, and use it in a
      few relevant places.
      
      This does make hugetlbfs not supported (not registered at all) in this
      environment.  I believe this is fine, as there are no valid hugepages
      and that won't change at runtime.
      
      [akpm@linux-foundation.org: use pr_info(), per Mel]
      [akpm@linux-foundation.org: fix build when HPAGE_SHIFT is undefined]
      Signed-off-by: default avatarNishanth Aravamudan <nacc@linux.vnet.ibm.com>
      Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
      Acked-by: default avatarMel Gorman <mgorman@suse.de>
      Cc: Randy Dunlap <rdunlap@infradead.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      457c1b27