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Andrea Arcangeli e4eed03fd0 thp: avoid atomic64_read in pmd_read_atomic for 32bit PAE 
In the x86 32bit PAE CONFIG_TRANSPARENT_HUGEPAGE=y case while holding the
mmap_sem for reading, cmpxchg8b cannot be used to read pmd contents under
Xen.

So instead of dealing only with "consistent" pmdvals in
pmd_none_or_trans_huge_or_clear_bad() (which would be conceptually
simpler) we let pmd_none_or_trans_huge_or_clear_bad() deal with pmdvals
where the low 32bit and high 32bit could be inconsistent (to avoid having
to use cmpxchg8b).

The only guarantee we get from pmd_read_atomic is that if the low part of
the pmd was found null, the high part will be null too (so the pmd will be
considered unstable).  And if the low part of the pmd is found "stable"
later, then it means the whole pmd was read atomically (because after a
pmd is stable, neither MADV_DONTNEED nor page faults can alter it anymore,
and we read the high part after the low part).

In the 32bit PAE x86 case, it is enough to read the low part of the pmdval
atomically to declare the pmd as "stable" and that's true for THP and no
THP, furthermore in the THP case we also have a barrier() that will
prevent any inconsistent pmdvals to be cached by a later re-read of the
*pmd.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Tested-by: Andrew Jones <drjones@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-20 14:39:35 -07:00
..
bitops Add #includes needed to permit the removal of asm/system.h 2012-03-28 18:30:03 +01:00
4level-fixup.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
atomic-long.h asm-generic: merge branch 'master' of torvalds/linux-2.6 2009-06-12 11:32:58 +02:00
atomic.h Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
atomic64.h lib: Provide generic atomic64_t implementation 2009-06-15 13:27:38 +10:00
audit_change_attr.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_dir_write.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_read.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_signal.h [PATCH] add SIGNAL syscall class (v3) 2007-05-11 05:38:25 -04:00
audit_write.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
auxvec.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
barrier.h Create asm-generic/barrier.h 2012-03-28 18:30:03 +01:00
bitops.h bitops: remove minix bitops from asm/bitops.h 2011-03-23 19:46:22 -07:00
bitsperlong.h vsprintf: further optimize decimal conversion 2012-05-31 17:49:27 -07:00
bug.h bug.h: need linux/kernel.h for TAINT_WARN. 2012-06-11 14:29:58 +09:00
bugs.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
cache.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
cacheflush.h asm-generic/cacheflush.h: flush icache when copying to user pages 2011-05-25 08:39:37 -07:00
checksum.h Add extra arch overrides to asm-generic/checksum.h 2011-11-01 07:34:21 -07:00
cmpxchg-local.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
cmpxchg.h asm-generic: add linux/types.h to cmpxchg.h 2012-04-02 14:41:27 -07:00
cputime.h Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 08:44:54 -08:00
current.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
delay.h asm-generic: delay.h fix udelay and ndelay for 8 bit args 2011-07-22 18:45:33 +02:00
device.h Driver Core: Add platform device arch data V3 2009-07-22 00:28:38 +02:00
div64.h rename div64_64 to div64_u64 2008-05-01 08:03:58 -07:00
dma-coherent.h common: add dma_mmap_from_coherent() function 2012-05-21 15:06:09 +02:00
dma-contiguous.h drivers: add Contiguous Memory Allocator 2012-05-21 15:09:37 +02:00
dma-mapping-broken.h dma-mapping: remove dma_is_consistent API 2010-08-11 08:59:21 -07:00
dma-mapping-common.h BUG: headers with BUG/BUG_ON etc. need linux/bug.h 2012-03-04 17:54:34 -05:00
dma.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
emergency-restart.h
errno-base.h
errno.h mm: make __get_user_pages return -EHWPOISON for HWPOISON page optionally 2011-03-17 13:08:27 -03:00
exec.h Split arch_align_stack() out from asm-generic/system.h 2012-03-28 18:30:03 +01:00
fb.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
fcntl.h locks: move F_INPROGRESS from fl_type to fl_flags field 2011-08-19 13:25:34 -04:00
ftrace.h asm-generic headers: add ftrace.h 2011-03-17 09:19:04 +08:00
futex.h futex: Sanitize futex ops argument types 2011-03-11 12:23:31 +01:00
getorder.h bitops: Add missing parentheses to new get_order macro 2012-02-24 10:39:27 -08:00
gpio.h gpiolib: Remove 'const' from data argument of gpiochip_find() 2012-05-18 23:01:05 -06:00
hardirq.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
hw_irq.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
ide_iops.h
int-l64.h asm-generic: introduce asm/bitsperlong.h 2009-06-11 21:02:14 +02:00
int-ll64.h asm-generic: introduce asm/bitsperlong.h 2009-06-11 21:02:14 +02:00
io-64-nonatomic-hi-lo.h asm-generic: architecture independent readq/writeq for 32bit environment 2012-02-21 16:47:28 -08:00
io-64-nonatomic-lo-hi.h asm-generic: architecture independent readq/writeq for 32bit environment 2012-02-21 16:47:28 -08:00
io.h lib: use generic pci_iomap on all architectures 2012-01-10 18:04:27 -08:00
ioctl.h Make ioctl.h compatible with userland 2008-08-12 16:07:31 -07:00
ioctls.h tty: add TIOCVHANGUP to allow clean tty shutdown of all ttys 2011-02-17 14:16:30 -08:00
iomap.h [PARISC] fix compile break caused by iomap: make IOPORT/PCI mapping functions conditional 2012-02-27 09:43:30 -06:00
ipcbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
irq.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
irq_regs.h core: Replace __get_cpu_var with __this_cpu_read if not used for an address. 2010-12-17 15:07:19 +01:00
irqflags.h Fix IRQ flag handling naming 2010-10-07 14:08:55 +01:00
Kbuild KVM: Export asm-generic/kvm_para.h 2012-05-29 12:31:01 +03:00
Kbuild.asm include: replace unifdef-y with header-y 2010-08-14 22:26:51 +02:00
kdebug.h asm-generic: kdebug.h: Checkpatch cleanup 2010-10-09 21:51:44 +02:00
kmap_types.h include/asm-generic/kmap_types.h: add helpful reminder 2010-05-25 08:07:03 -07:00
kvm_para.h KVM: make asm-generic/kvm_para.h have an ifdef __KERNEL__ block 2012-05-21 17:47:52 +03:00
libata-portmap.h libata-portmap: Remove unused definitions 2007-10-12 14:55:37 -04:00
linkage.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
local.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
local64.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
memory_model.h mm: fix __page_to_pfn for a const struct page argument 2011-08-17 13:00:20 -07:00
mm_hooks.h [PATCH] x86: PARAVIRT: add hooks to intercept mm creation and destruction 2007-05-02 19:27:14 +02:00
mman-common.h coredump: add VM_NODUMP, MADV_NODUMP, MADV_CLEAR_NODUMP 2012-03-23 16:58:42 -07:00
mman.h mm: add MAP_HUGETLB for mmaping pseudo-anonymous huge page regions 2009-09-22 07:17:41 -07:00
mmu.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
mmu_context.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
module.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
msgbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
mutex-dec.h mutex: speed up generic mutex implementations 2008-10-23 09:18:20 -07:00
mutex-null.h
mutex-xchg.h mutex: speed up generic mutex implementations 2008-10-23 09:18:20 -07:00
mutex.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
page.h The following changes since commit 3ee72ca992 2012-01-10 17:39:40 -08:00
param.h UAPI: Rearrange definition of HZ in asm-generic/param.h 2011-12-13 09:26:45 +00:00
parport.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
pci-bridge.h PCI: work around Stratus ftServer broken PCIe hierarchy 2012-04-30 15:21:02 -06:00
pci-dma-compat.h dma-mapping: pci: move pci_set_dma_mask and pci_set_consistent_dma_mask to pci-dma-compat.h 2010-03-12 15:52:42 -08:00
pci.h PCI: collapse pcibios_resource_to_bus 2012-02-23 20:19:04 -07:00
pci_iomap.h [PARISC] fix compile break caused by iomap: make IOPORT/PCI mapping functions conditional 2012-02-27 09:43:30 -06:00
percpu.h percpu: Optimize __get_cpu_var() 2010-09-10 10:56:51 +02:00
pgalloc.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
pgtable-nopmd.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
pgtable-nopud.h mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() 2009-07-27 12:10:38 -07:00
pgtable.h thp: avoid atomic64_read in pmd_read_atomic for 32bit PAE 2012-06-20 14:39:35 -07:00
poll.h epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree() 2012-02-24 11:42:50 -08:00
posix_types.h bury __kernel_nlink_t, make internal nlink_t consistent 2012-05-30 21:04:50 -04:00
ptrace.h asm-generic/ptrace.h: start a common low level ptrace helper 2011-05-26 17:12:36 -07:00
resource.h ulimit: raise default hard ulimit on number of files to 4096 2011-05-25 08:39:43 -07:00
rtc.h asm-generic: make get_rtc_time overridable 2009-06-11 21:02:18 +02:00
rwsem.h Hexagon: Add locking types and functions 2011-11-01 07:34:20 -07:00
scatterlist.h asm-generic: remove ARCH_HAS_SG_CHAIN in scatterlist.h 2010-05-27 09:12:54 -07:00
sections.h x86: Separate out entry text section 2011-03-08 17:22:11 +01:00
segment.h asm-generic: add generic NOMMU versions of some headers 2009-06-11 21:02:50 +02:00
sembuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
serial.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
setup.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
shmbuf.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
shmparam.h asm-generic: add generic sysv ipc headers 2009-06-11 21:02:15 +02:00
siginfo.h Linux 3.4-rc5 2012-05-04 12:46:40 +10:00
signal-defs.h asm-generic: rename termios.h, signal.h and mman.h 2009-06-11 21:01:52 +02:00
signal.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
sizes.h asm-generic headers: add sizes.h 2011-03-17 09:19:04 +08:00
socket.h net: Add framework to allow sending packets with customized CRC. 2012-02-24 01:37:35 -08:00
sockios.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
spinlock.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
stat.h asm-generic/stat.h: support 64-bit file time_t for stat() 2010-11-01 15:31:29 -04:00
statfs.h asm-generic: Use __BITS_PER_LONG in statfs.h 2012-04-30 12:55:15 -07:00
string.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
swab.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
switch_to.h Split the switch_to() wrapper out of asm-generic/system.h 2012-03-28 18:30:03 +01:00
syscall.h asm/syscall.h: add syscall_get_arch 2012-04-14 11:13:19 +10:00
syscalls.h Fix the declaration of sys_execve() in asm-generic/syscalls.h 2010-08-18 12:12:38 -07:00
termbits.h tty: Add EXTPROC support for LINEMODE 2010-08-10 13:47:39 -07:00
termios-base.h asm-generic: rename termios.h, signal.h and mman.h 2009-06-11 21:01:52 +02:00
termios.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
timex.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
tlb.h thp: add tlb_remove_pmd_tlb_entry 2012-01-12 20:13:08 -08:00
tlbflush.h BUG: headers with BUG/BUG_ON etc. need linux/bug.h 2012-03-04 17:54:34 -05:00
topology.h topology: alternate fix for ia64 tiger_defconfig build breakage 2010-08-09 20:44:57 -07:00
types.h consolidate umode_t declarations 2012-01-03 22:55:17 -05:00
uaccess-unaligned.h asm-generic: rename page.h and uaccess.h 2009-06-11 21:02:17 +02:00
uaccess.h fix default __strnlen_user macro 2011-10-06 19:47:12 -04:00
ucontext.h asm-generic: add generic ABI headers 2009-06-11 21:02:15 +02:00
unaligned.h asm-generic: add generic versions of common headers 2009-06-11 21:02:37 +02:00
unistd.h compat: use sys_sendfile64() implementation for sendfile syscall 2012-03-27 13:36:57 -04:00
user.h asm-generic/user.h: Fix spelling in comment 2011-03-01 15:49:39 +01:00
vga.h asm-generic: add legacy I/O header files 2009-06-11 21:02:42 +02:00
vmlinux.lds.h ftrace: Sort all function addresses, not just per page 2012-05-16 19:58:44 -04:00
word-at-a-time.h word-at-a-time: make the interfaces truly generic 2012-05-26 11:33:40 -07:00
xor.h sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00