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SubjectRe: [PATCH 1/2 V2] memory-hotplug: fix BUG_ON in move_freepages()
Hi Xishi,
On 04/18/2015 04:05 AM, Yasuaki Ishimatsu wrote:

>
> Your patches will fix your issue.
> But, if BIOS reports memory first at node hot add, pgdat can
> not be initialized.
>
> Memory hot add flows are as follows:
>
> add_memory
> ...
> -> hotadd_new_pgdat()
> ...
> -> node_set_online(nid)
>
> When calling hotadd_new_pgdat() for a hot added node, the node is
> offline because node_set_online() is not called yet. So if applying
> your patches, the pgdat is not initialized in this case.

Ishimtasu's worry is reasonable. And I am afraid the fix here is a bit
over-kill.

>
> Thanks,
> Yasuaki Ishimatsu
>
> On Fri, 17 Apr 2015 18:50:32 +0800
> Xishi Qiu <qiuxishi@huawei.com> wrote:
>
>> Hot remove nodeXX, then hot add nodeXX. If BIOS report cpu first, it will call
>> hotadd_new_pgdat(nid, 0), this will set pgdat->node_start_pfn to 0. As nodeXX
>> exists at boot time, so pgdat->node_spanned_pages is the same as original. Then
>> free_area_init_core()->memmap_init() will pass a wrong start and a nonzero size.

As your analysis said the root cause here is passing a *0* as the node_start_pfn,
then the chaos occurred when init the zones. And this only happens to the re-hotadd
node, so how about using the saved *node_start_pfn* (via get_pfn_range_for_nid(nid, &start_pfn, &end_pfn))
instead if we find "pgdat->node_start_pfn == 0 && !node_online(XXX)"?

Thanks,
Gu

>>
>> free_area_init_core()
>> memmap_init()
>> memmap_init_zone()
>> early_pfn_in_nid()
>> set_page_links()
>>
>> "if (!early_pfn_in_nid(pfn, nid))" will skip the pfn(memory in section), but it
>> will not skip the pfn(hole in section), this will cover and relink the page to
>> zone/nid, so page_zone() from memory and hole in the same section are different.
>> The following call trace shows the bug.
>>
>> This patch will set the node size to 0 when hotadd a new node(original or new).
>> init_currently_empty_zone() and memmap_init() will be called in add_zone(), so
>> need not to change it.
>>
>> [90476.077469] kernel BUG at mm/page_alloc.c:1042! // move_freepages() -> BUG_ON(page_zone(start_page) != page_zone(end_page));
>> [90476.077469] invalid opcode: 0000 [#1] SMP
>> [90476.077469] Modules linked in: iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack fuse btrfs zlib_deflate raid6_pq xor msdos ext4 mbcache jbd2 binfmt_misc bridge stp llc ip6table_filter ip6_tables iptable_filter ip_tables ebtable_nat ebtables cfg80211 rfkill sg iTCO_wdt iTCO_vendor_support intel_powerclamp coretemp intel_rapl kvm_intel kvm crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr igb vfat i2c_algo_bit dca fat sb_edac edac_core i2c_i801 lpc_ich i2c_core mfd_core shpchp acpi_pad ipmi_si ipmi_msghandler uinput nfsd auth_rpcgss nfs_acl lockd sunrpc xfs libcrc32c sd_mod crc_t10dif crct10dif_common ahci libahci megaraid_sas tg3 ptp libata pps_core dm_mirror dm_region_hash dm_log dm_mod [last unloaded: rasf]
>> [90476.157382] CPU: 2 PID: 322803 Comm: updatedb Tainted: GF W O-------------- 3.10.0-229.1.2.5.hulk.rc14.x86_64 #1
>> [90476.157382] Hardware name: HUAWEI TECHNOLOGIES CO.,LTD. Huawei N1/Huawei N1, BIOS V100R001 04/13/2015
>> [90476.157382] task: ffff88006a6d5b00 ti: ffff880068eb8000 task.ti: ffff880068eb8000
>> [90476.157382] RIP: 0010:[<ffffffff81159f7f>] [<ffffffff81159f7f>] move_freepages+0x12f/0x140
>> [90476.157382] RSP: 0018:ffff880068ebb640 EFLAGS: 00010002
>> [90476.157382] RAX: ffff880002316cc0 RBX: ffffea0001bd0000 RCX: 0000000000000001
>> [90476.157382] RDX: ffff880002476e40 RSI: 0000000000000000 RDI: ffff880002316cc0
>> [90476.157382] RBP: ffff880068ebb690 R08: 0000000000100000 R09: ffffea0001bd7fc0
>> [90476.157382] R10: 000000000006f5ff R11: 0000000000000000 R12: 0000000000000001
>> [90476.157382] R13: 0000000000000003 R14: ffff880002316eb8 R15: ffffea0001bd7fc0
>> [90476.157382] FS: 00007f4d3ab95740(0000) GS:ffff880033a00000(0000) knlGS:0000000000000000
>> [90476.157382] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [90476.157382] CR2: 00007f4d3ae1a808 CR3: 000000018907a000 CR4: 00000000001407e0
>> [90476.157382] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> [90476.157382] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> [90476.157382] Stack:
>> [90476.157382] ffff880068ebb698 ffff880002316cc0 ffffa800b5378098 ffff880068ebb698
>> [90476.157382] ffffffff810b11dc ffff880002316cc0 0000000000000001 0000000000000003
>> [90476.157382] ffff880002316eb8 ffffea0001bd6420 ffff880068ebb6a0 ffffffff8115a003
>> [90476.157382] Call Trace:
>> [90476.157382] [<ffffffff810b11dc>] ? update_curr+0xcc/0x150
>> [90476.157382] [<ffffffff8115a003>] move_freepages_block+0x73/0x80
>> [90476.157382] [<ffffffff8115b9ba>] __rmqueue+0x26a/0x460
>> [90476.157382] [<ffffffff8101ba53>] ? native_sched_clock+0x13/0x80
>> [90476.157382] [<ffffffff8115e172>] get_page_from_freelist+0x7f2/0xd30
>> [90476.157382] [<ffffffff81012639>] ? __switch_to+0x179/0x4a0
>> [90476.157382] [<ffffffffa01fc0d7>] ? xfs_iext_bno_to_ext+0xa7/0x1a0 [xfs]
>> [90476.157382] [<ffffffff8115e871>] __alloc_pages_nodemask+0x1c1/0xc90
>> [90476.157382] [<ffffffffa01ab24c>] ? _xfs_buf_ioapply+0x31c/0x420 [xfs]
>> [90476.157382] [<ffffffff8109cb0d>] ? down_trylock+0x2d/0x40
>> [90476.157382] [<ffffffffa01abfff>] ? xfs_buf_trylock+0x1f/0x80 [xfs]
>> [90476.157382] [<ffffffff8119d229>] alloc_pages_current+0xa9/0x170
>> [90476.157382] [<ffffffff811a7225>] new_slab+0x275/0x300
>> [90476.157382] [<ffffffff815faaa2>] __slab_alloc+0x315/0x48f
>> [90476.157382] [<ffffffffa01c59d7>] ? kmem_zone_alloc+0x77/0x100 [xfs]
>> [90476.157382] [<ffffffffa01d21fc>] ? xfs_bmap_search_extents+0x5c/0xc0 [xfs]
>> [90476.157382] [<ffffffff811a9863>] kmem_cache_alloc+0x193/0x1d0
>> [90476.157382] [<ffffffffa01c59d7>] ? kmem_zone_alloc+0x77/0x100 [xfs]
>> [90476.157382] [<ffffffffa01c59d7>] kmem_zone_alloc+0x77/0x100 [xfs]
>> [90476.157382] [<ffffffffa01b46b5>] xfs_inode_alloc+0x25/0x250 [xfs]
>> [90476.157382] [<ffffffffa01b5279>] xfs_iget+0x219/0x680 [xfs]
>> [90476.157382] [<ffffffffa01f83a6>] xfs_lookup+0xf6/0x120 [xfs]
>> [90476.157382] [<ffffffffa01bae1b>] xfs_vn_lookup+0x7b/0xd0 [xfs]
>> [90476.157382] [<ffffffff811ce40d>] lookup_real+0x1d/0x50
>> [90476.157382] [<ffffffff811ced42>] __lookup_hash+0x42/0x60
>> [90476.157382] [<ffffffff815fae0c>] lookup_slow+0x42/0xa7
>> [90476.157382] [<ffffffff811d28cb>] path_lookupat+0x76b/0x7a0
>> [90476.157382] [<ffffffff811d3815>] ? do_last+0x635/0x1260
>> [90476.157382] [<ffffffff811a9705>] ? kmem_cache_alloc+0x35/0x1d0
>> [90476.157382] [<ffffffff811d498f>] ? getname_flags+0x4f/0x190
>> [90476.157382] [<ffffffff811d292b>] filename_lookup+0x2b/0xc0
>> [90476.157382] [<ffffffff811d5807>] user_path_at_empty+0x67/0xc0
>> [90476.157382] [<ffffffff810efaa2>] ? from_kgid_munged+0x12/0x20
>> [90476.157382] [<ffffffff811c991f>] ? cp_new_stat+0x14f/0x180
>> [90476.157382] [<ffffffff811d5871>] user_path_at+0x11/0x20
>> [90476.157382] [<ffffffff811c9413>] vfs_fstatat+0x63/0xc0
>> [90476.157382] [<ffffffff811c99e1>] SYSC_newlstat+0x31/0x60
>> [90476.157382] [<ffffffff810f9b16>] ? __audit_syscall_exit+0x1f6/0x2a0
>> [90476.157382] [<ffffffff811c9c5e>] SyS_newlstat+0xe/0x10
>> [90476.157382] [<ffffffff8160ca69>] system_call_fastpath+0x16/0x1b
>> [90476.157382] Code: d0 8b 45 c4 48 c1 e2 06 48 01 d3 01 c8 49 39 df 0f 83 7b ff ff ff 66 0f 1f 44 00 00 48 83 c4 28 5b 41 5c 41 5d 41 5e 41 5f 5d c3 <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
>> [90476.157382] RIP [<ffffffff81159f7f>] move_freepages+0x12f/0x140
>> [90476.157382] RSP <ffff880068ebb640>
>> [90476.157382] ---[ end trace 58557f791c6d66d4 ]---
>> [90476.157382] Kernel panic - not syncing: Fatal exception
>>
>> log and analyse:
>> ...
>> [ 0.000000] Initmem setup node 0 [mem 0x00000000-0x2000ffffffff]
>> [ 0.000000] NODE_DATA [mem 0x02312400-0x023393ff] // node0
>> ...
>> [ 0.000000] Initmem setup node 9 [mem 0x30000000000-0x3ffffffffff]
>> [ 0.000000] NODE_DATA [mem 0x02471400-0x024983ff] // node9
>> ...
>> [ 0.000000] node 0: [mem 0x5b880000-0x5baf2fff]
>> [ 0.000000] node 0: [mem 0x61382000-0x6148ffff]
>> [ 0.000000] node 0: [mem 0x61a90000-0x6f39bfff] // 1562.56 - 1779.61
>> [ 0.000000] node 0: [mem 0x6f51c000-0x6f7c9fff] // 1781.11 - 1783.79
>> [ 0.000000] node 0: [mem 0x6fb1c000-0x6fb1cfff]
>> [ 0.000000] node 0: [mem 0x6fba3000-0x6fffffff]
>> ...
>>
>> start_page = ffffea0001bd0000 -> pfn=0x6F400 -> 1780M, in node0, right!
>> end_page = ffffea0001bd7fc0 -> pfn=0x6F5FF -> 1782M-4kb, in node0, right!
>> page_zone(start_page) = ffff880002476e40, in node9, wrong!
>> page_zone(end_page) = ffff880002316cc0, in node0, right!
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>> ---
>> mm/page_alloc.c | 14 ++++++++++++++
>> 1 files changed, 14 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index ebffa0e..f74398c 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -4667,6 +4667,10 @@ static unsigned long __meminit zone_spanned_pages_in_node(int nid,
>> {
>> unsigned long zone_start_pfn, zone_end_pfn;
>>
>> + /* When hotadd a new node, init node's zones as empty zones */
>> + if (!node_online(nid))
>> + return 0;
>> +
>> /* Get the start and end of the zone */
>> zone_start_pfn = arch_zone_lowest_possible_pfn[zone_type];
>> zone_end_pfn = arch_zone_highest_possible_pfn[zone_type];
>> @@ -4730,6 +4734,10 @@ static unsigned long __meminit zone_absent_pages_in_node(int nid,
>> unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
>> unsigned long zone_start_pfn, zone_end_pfn;
>>
>> + /* When hotadd a new node, init node's zones as empty zones */
>> + if (!node_online(nid))
>> + return 0;
>> +
>> zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
>> zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
>>
>> @@ -4746,6 +4754,9 @@ static inline unsigned long __meminit zone_spanned_pages_in_node(int nid,
>> unsigned long node_end_pfn,
>> unsigned long *zones_size)
>> {
>> + if (!node_online(nid))
>> + return 0;
>> +
>> return zones_size[zone_type];
>> }
>>
>> @@ -4755,6 +4766,9 @@ static inline unsigned long __meminit zone_absent_pages_in_node(int nid,
>> unsigned long node_end_pfn,
>> unsigned long *zholes_size)
>> {
>> + if (!node_online(nid))
>> + return 0;
>> +
>> if (!zholes_size)
>> return 0;
>>
>> --
>> 1.7.1
>>
>>
>>
>> --
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> .
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