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    Subject[PATCH 3.13.y-ckt 33/90] mm/memory hotplug: postpone the reset of obsolete pgdat
    Date
    3.13.11-ckt20 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Gu Zheng <guz.fnst@cn.fujitsu.com>

    commit b0dc3a342af36f95a68fe229b8f0f73552c5ca08 upstream.

    Qiu Xishi reported the following BUG when testing hot-add/hot-remove node under
    stress condition:

    BUG: unable to handle kernel paging request at 0000000000025f60
    IP: next_online_pgdat+0x1/0x50
    PGD 0
    Oops: 0000 [#1] SMP
    ACPI: Device does not support D3cold
    Modules linked in: fuse nls_iso8859_1 nls_cp437 vfat fat loop dm_mod coretemp mperf crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul glue_helper aes_x86_64 pcspkr microcode igb dca i2c_algo_bit ipv6 megaraid_sas iTCO_wdt i2c_i801 i2c_core iTCO_vendor_support tg3 sg hwmon ptp lpc_ich pps_core mfd_core acpi_pad rtc_cmos button ext3 jbd mbcache sd_mod crc_t10dif scsi_dh_alua scsi_dh_rdac scsi_dh_hp_sw scsi_dh_emc scsi_dh ahci libahci libata scsi_mod [last unloaded: rasf]
    CPU: 23 PID: 238 Comm: kworker/23:1 Tainted: G O 3.10.15-5885-euler0302 #1
    Hardware name: HUAWEI TECHNOLOGIES CO.,LTD. Huawei N1/Huawei N1, BIOS V100R001 03/02/2015
    Workqueue: events vmstat_update
    task: ffffa800d32c0000 ti: ffffa800d32ae000 task.ti: ffffa800d32ae000
    RIP: 0010: next_online_pgdat+0x1/0x50
    RSP: 0018:ffffa800d32afce8 EFLAGS: 00010286
    RAX: 0000000000001440 RBX: ffffffff81da53b8 RCX: 0000000000000082
    RDX: 0000000000000000 RSI: 0000000000000082 RDI: 0000000000000000
    RBP: ffffa800d32afd28 R08: ffffffff81c93bfc R09: ffffffff81cbdc96
    R10: 00000000000040ec R11: 00000000000000a0 R12: ffffa800fffb3440
    R13: ffffa800d32afd38 R14: 0000000000000017 R15: ffffa800e6616800
    FS: 0000000000000000(0000) GS:ffffa800e6600000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000025f60 CR3: 0000000001a0b000 CR4: 00000000001407e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    refresh_cpu_vm_stats+0xd0/0x140
    vmstat_update+0x11/0x50
    process_one_work+0x194/0x3d0
    worker_thread+0x12b/0x410
    kthread+0xc6/0xd0
    ret_from_fork+0x7c/0xb0

    The cause is the "memset(pgdat, 0, sizeof(*pgdat))" at the end of
    try_offline_node, which will reset all the content of pgdat to 0, as the
    pgdat is accessed lock-free, so that the users still using the pgdat
    will panic, such as the vmstat_update routine.

    process A: offline node XX:

    vmstat_updat()
    refresh_cpu_vm_stats()
    for_each_populated_zone()
    find online node XX
    cond_resched()
    offline cpu and memory, then try_offline_node()
    node_set_offline(nid), and memset(pgdat, 0, sizeof(*pgdat))
    zone = next_zone(zone)
    pg_data_t *pgdat = zone->zone_pgdat; // here pgdat is NULL now
    next_online_pgdat(pgdat)
    next_online_node(pgdat->node_id); // NULL pointer access

    So the solution here is postponing the reset of obsolete pgdat from
    try_offline_node() to hotadd_new_pgdat(), and just resetting
    pgdat->nr_zones and pgdat->classzone_idx to be 0 rather than the memset
    0 to avoid breaking pointer information in pgdat.

    Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
    Reported-by: Xishi Qiu <qiuxishi@huawei.com>
    Suggested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
    Cc: Tang Chen <tangchen@cn.fujitsu.com>
    Cc: Xie XiuQi <xiexiuqi@huawei.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    mm/memory_hotplug.c | 13 ++++---------
    1 file changed, 4 insertions(+), 9 deletions(-)

    diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
    index 489f235..38c966a 100644
    --- a/mm/memory_hotplug.c
    +++ b/mm/memory_hotplug.c
    @@ -1017,6 +1017,10 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
    return NULL;

    arch_refresh_nodedata(nid, pgdat);
    + } else {
    + /* Reset the nr_zones and classzone_idx to 0 before reuse */
    + pgdat->nr_zones = 0;
    + pgdat->classzone_idx = 0;
    }

    /* we can use NODE_DATA(nid) from here */
    @@ -1862,15 +1866,6 @@ void try_offline_node(int nid)
    if (is_vmalloc_addr(zone->wait_table))
    vfree(zone->wait_table);
    }
    -
    - /*
    - * Since there is no way to guarentee the address of pgdat/zone is not
    - * on stack of any kernel threads or used by other kernel objects
    - * without reference counting or other symchronizing method, do not
    - * reset node_data and free pgdat here. Just reset it to 0 and reuse
    - * the memory when the node is online again.
    - */
    - memset(pgdat, 0, sizeof(*pgdat));
    }
    EXPORT_SYMBOL(try_offline_node);

    --
    1.9.1


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