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    SubjectRe: [PATCH v3] mm: make expand_downwards symmetrical to expand_upwards
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    On Tue, 2011-04-19 at 13:10 +0200, Michal Hocko wrote:
    > On Mon 18-04-11 13:56:37, Andrew Morton wrote:
    > > On Mon, 18 Apr 2011 12:01:31 +0200
    > > Michal Hocko <mhocko@suse.cz> wrote:
    > >
    > > > Currently we have expand_upwards exported while expand_downwards is
    > > > accessible only via expand_stack or expand_stack_downwards.
    > > >
    > > > check_stack_guard_page is a nice example of the asymmetry. It uses
    > > > expand_stack for VM_GROWSDOWN while expand_upwards is called for
    > > > VM_GROWSUP case.
    > > >
    > > > Let's clean this up by exporting both functions and make those name
    > > > consistent. Let's use expand_stack_{upwards,downwards} so that we are
    > > > explicit about stack manipulation in the name. expand_stack_downwards
    > > > has to be defined for both CONFIG_STACK_GROWS{UP,DOWN} because
    > > > get_arg_page calls the downwards version in the early process
    > > > initialization phase for growsup configuration.
    > >
    > > Has this patch been tested on any stack-grows-upwards architecture?
    >
    > The only one I can find in the tree is parisc and I do not have access
    > to any such machine. Maybe someone on the list (CCed) can help with
    > testing the patch bellow? Nevertheless, the patch doesn't change growsup
    > case. It just renames functions and exports growsdown.

    It compiles OK, but crashes on boot in fsck. The crash is definitely mm
    but looks to be a slab problem (it's a null deref on a spinlock in
    add_partial(), which seems unrelated to this patch).

    [ 15.628000] sd 1:0:2:0: [sdc] Attached SCSI disk
    done.
    [ 16.632000] EXT3-fs: barriers not enabled
    [ 16.640000] kjournald starting. Commit interval 5 seconds
    [ 16.640000] EXT3-fs (sda3): mounted filesystem with ordered data mode
    Begin: Running /scripts/local-bottom ... done.
    done.
    Begin: Running /scripts/init-bottom ... done.
    INIT: version 2.88 booting
    Setting hostname to 'ion'...done.
    Starting the hotplug events dispatcher: udevd[ 22.008000] udev[211]: starting version 164
    .
    Synthesizing the initial hotplug events...done.
    Waiting for /dev to be fully populated...done.
    Activating swap:swapon on /dev/sda2
    swapon: /dev/sda2: found swap signature: version 1, page-size 4, same byte order
    swapon: /dev/sda2: pagesize=4096, swapsize=1028157440, devsize=1028160000
    [ 28.780000] Adding 1004056k swap on /dev/sda2. Priority:-1 extents:1 across:1004056k
    .
    Will now check root file system:fsck from util-linux-ng 2.17.2
    [/sbin/fsck.ext3 (1) -- /] fsck.ext3 -a -C0 /dev/sda3
    /dev/sda3 has been mounted 37 times without being checked, check forced.
    [ 257.192000] Backtrace:=========== \ 42.8%
    [ 257.192000] [<0000000040214f78>] add_partial+0x28/0x98
    [ 257.192000] [<0000000040217ff8>] __slab_free+0x1d0/0x1d8
    [ 257.192000] [<000000004021825c>] kmem_cache_free+0xc4/0x128
    [ 257.192000] [<00000000401fd1a4>] remove_vma+0x8c/0xc0
    [ 257.192000] [<00000000401fd3a8>] exit_mmap+0x1d0/0x220
    [ 257.192000] [<0000000040156514>] mmput+0xd4/0x200
    [ 257.192000] [<000000004015c7b8>] exit_mm+0x100/0x2c0
    [ 257.192000] [<000000004015ef40>] do_exit+0x778/0x9d8
    [ 257.192000] [<000000004015f1ec>] do_group_exit+0x4c/0xe0
    [ 257.192000] [<000000004015f298>] sys_exit_group+0x18/0x28
    [ 257.192000] [<0000000040106034>] syscall_exit+0x0/0x14
    [ 257.192000]
    [ 257.192000]
    [ 257.192000] Kernel Fault: Code=26 regs=00000040bf1807d0 (Addr=0000000000000000)
    [ 257.192000]
    [ 257.192000] YZrvWESTHLNXBCVMcbcbcbcbOGFRQPDI
    [ 257.192000] PSW: 00001000000001001111000000001110 Not tainted
    [ 257.192000] r00-03 000000ff0804f00e 0000000040769e40 0000000040214f78 0000000000000000
    [ 257.192000] r04-07 0000000040746e40 0000000000000001 0000004080ded370 0000000000000001
    [ 257.192000] r08-11 0000000040654150 0000000000000000 0000000000000001 0000000000000001
    [ 257.192000] r12-15 0000000000000000 00000000ffffffff 0000000000000024 0000000000000000
    [ 257.192000] r16-19 00000000fb4ead9c 00000000fb4eac54 0000000000000000 0000000000000000
    [ 257.192000] r20-23 000000000800000e 0000000000000001 000000007bbb7180 00000000401fd1a4
    [ 257.192000] r24-27 0000000000000001 0000004080ded370 0000000000000000 0000000040746e40
    [ 257.192000] r28-31 000000007ec0a908 00000040bf1807a0 00000040bf1807d0 0000000000000016
    [ 257.192000] sr00-03 00000000002d9000 0000000000000000 0000000000000000 00000000002d9000
    [ 257.192000] sr04-07 0000000000000000 0000000000000000 0000000000000000 0000000000000000
    [ 257.192000]
    [ 257.192000] IASQ: 0000000000000000 0000000000000000 IAOQ: 000000004011bbc0 000000004011bbc4
    [ 257.192000] IIR: 0f4015dc ISR: 0000000000000000 IOR: 0000000000000000
    [ 257.192000] CPU: 0 CR30: 00000040bf180000 CR31: fffffff0f0e098e0
    [ 257.192000] ORIG_R28: 0000000040769e40
    [ 257.192000] IAOQ[0]: _raw_spin_lock+0x0/0x20
    [ 257.192000] IAOQ[1]: _raw_spin_lock+0x4/0x20
    [ 257.192000] RP(r2): add_partial+0x28/0x98
    [ 257.192000] Backtrace:
    [ 257.192000] [<0000000040214f78>] add_partial+0x28/0x98
    [ 257.192000] [<0000000040217ff8>] __slab_free+0x1d0/0x1d8
    [ 257.192000] [<000000004021825c>] kmem_cache_free+0xc4/0x128
    [ 257.192000] [<00000000401fd1a4>] remove_vma+0x8c/0xc0
    [ 257.192000] [<00000000401fd3a8>] exit_mmap+0x1d0/0x220
    [ 257.192000] [<0000000040156514>] mmput+0xd4/0x200
    [ 257.192000] [<000000004015c7b8>] exit_mm+0x100/0x2c0
    [ 257.192000] [<000000004015ef40>] do_exit+0x778/0x9d8
    [ 257.192000] [<000000004015f1ec>] do_group_exit+0x4c/0xe0
    [ 257.192000] [<000000004015f298>] sys_exit_group+0x18/0x28
    [ 257.192000] [<0000000040106034>] syscall_exit+0x0/0x14
    [ 257.192000]
    [ 257.192000] Kernel panic - not syncing: Kernel Fault
    [ 257.192000] Backtrace:
    [ 257.192000] [<000000004011f984>] show_stack+0x14/0x20
    [ 257.192000] [<000000004011f9a8>] dump_stack+0x18/0x28
    [ 257.192000] [<000000004015946c>] panic+0xd4/0x368
    [ 257.192000] [<0000000040120024>] parisc_terminate+0x14c/0x170
    [ 257.192000] [<000000004012059c>] handle_interruption+0x2ac/0x8f8
    [ 257.192000] [<000000004011bbc0>] _raw_spin_lock+0x0/0x20
    [ 257.192000]
    [ 257.192000] Rebooting in 5 seconds..

    It seems to be a random intermittent mm crash because the next reboot
    crashed with the same trace but after the fsck had completed and the
    third came up to the login prompt.

    James




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