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Message-ID: <52170DDE.4010103@jp.fujitsu.com>
Date: Fri, 23 Aug 2013 16:23:10 +0900
From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To: Russ Anderson <rja@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH] [BUGFIX] drivers/base: fix show_mem_removable section
count
(2013/08/23 11:38), Russ Anderson wrote:
> "cat /sys/devices/system/memory/memory*/removable" crashed the system.
>
> The problem is that show_mem_removable() is passing a
> bad pfn to is_mem_section_removable(), which causes
> if (!node_online(page_to_nid(page))) to blow up.
> Why is it passing in a bad pfn?
>
> show_mem_removable() will loop sections_per_block times.
> sections_per_block is 16, but mem->section_count is 8
> for this memory block. Changing to loop the actual number
> of sections (mem->section_count) fixes the problem.
> The assumption that all memory blocks will have the same
> sections_per_block is not always true.
>
> I suspect other usages of sections_per_block will also
> need to be fixed.
>
> Signed-off-by: Russ Anderson <rja@....com>
>
>
> The failing output:
> -----------------------------------------------------------
> harp5-sys:~ # cat /sys/devices/system/memory/memory*/removable
> 0
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> 1
> [ 372.111178] BUG: unable to handle kernel paging request at ffffea00c3200000
> [ 372.119230] IP: [<ffffffff81117ed1>] is_pageblock_removable_nolock+0x1/0x90
> [ 372.127022] PGD 83ffd4067 PUD 37bdfce067 PMD 0
> [ 372.132109] Oops: 0000 [#1] SMP
> [ 372.135730] Modules linked in: autofs4 binfmt_misc rdma_ucm rdma_cm iw_cm ib_addr ib_srp scsi_transport_srp scsi_tgt ib_ipoib ib_cm ib_uverbs ib_umad iw_cxgb3 cxgb3 mdio mlx4_en mlx4_ib ib_sa mlx4_core ib_mthca ib_mad ib_core fuse nls_iso8859_1 nls_cp437 vfat fat joydev loop hid_generic usbhid hid hwperf(O) numatools(O) dm_mod iTCO_wdt ipv6 iTCO_vendor_support igb i2c_i801 ioatdma i2c_algo_bit ehci_pci pcspkr lpc_ich i2c_core ehci_hcd ptp sg mfd_core dca rtc_cmos pps_core mperf button xhci_hcd sd_mod crc_t10dif usbcore usb_common scsi_dh_emc scsi_dh_hp_sw scsi_dh_alua scsi_dh_rdac scsi_dh gru(O) xvma(O) xfs crc32c libcrc32c thermal sata_nv processor piix mptsas mptscsih scsi_transport_sas mptbase megaraid_sas fan thermal_sys hwmon ext3 jbd ata_piix ahci libahci libata scsi_mod
> [ 372.213536] CPU: 4 PID: 5991 Comm: cat Tainted: G O 3.11.0-rc5-rja-uv+ #10
> [ 372.222173] Hardware name: SGI UV2000/ROMLEY, BIOS SGI UV 2000/3000 series BIOS 01/15/2013
> [ 372.231391] task: ffff88081f034580 ti: ffff880820022000 task.ti: ffff880820022000
> [ 372.239737] RIP: 0010:[<ffffffff81117ed1>] [<ffffffff81117ed1>] is_pageblock_removable_nolock+0x1/0x90
> [ 372.250229] RSP: 0018:ffff880820023df8 EFLAGS: 00010287
> [ 372.256151] RAX: 0000000000040000 RBX: ffffea00c3200000 RCX: 0000000000000004
> [ 372.264111] RDX: ffffea00c30b0000 RSI: 00000000001c0000 RDI: ffffea00c3200000
> [ 372.272071] RBP: ffff880820023e38 R08: 0000000000000000 R09: 0000000000000001
> [ 372.280030] R10: 0000000000000000 R11: 0000000000000001 R12: ffffea00c33c0000
> [ 372.287987] R13: 0000160000000000 R14: 6db6db6db6db6db7 R15: 0000000000000001
> [ 372.295945] FS: 00007ffff7fb2700(0000) GS:ffff88083fc80000(0000) knlGS:0000000000000000
> [ 372.304970] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 372.311378] CR2: ffffea00c3200000 CR3: 000000081b954000 CR4: 00000000000407e0
> [ 372.319335] Stack:
> [ 372.321575] ffff880820023e38 ffffffff81161e94 ffffffff81d9e940 0000000000000009
> [ 372.329872] 0000000000000000 ffff8817bb97b800 ffff88081e928000 ffff8817bb97b870
> [ 372.338167] ffff880820023e68 ffffffff813730d1 fffffffffffffffb ffffffff81a97600
> [ 372.346463] Call Trace:
> [ 372.349201] [<ffffffff81161e94>] ? is_mem_section_removable+0x84/0x110
> [ 372.356579] [<ffffffff813730d1>] show_mem_removable+0x41/0x70
> [ 372.363094] [<ffffffff8135be8a>] dev_attr_show+0x2a/0x60
> [ 372.369122] [<ffffffff811e1817>] sysfs_read_file+0xf7/0x1c0
> [ 372.375441] [<ffffffff8116e7e8>] vfs_read+0xc8/0x130
> [ 372.381076] [<ffffffff8116ee5d>] SyS_read+0x5d/0xa0
> [ 372.386624] [<ffffffff814bfa12>] system_call_fastpath+0x16/0x1b
> [ 372.393313] Code: 01 00 00 00 e9 3c ff ff ff 90 0f b6 4a 30 44 89 d8 d3 e0 89 c1 83 e9 01 48 63 c9 49 01 c8 eb 92 66 2e 0f 1f 84 00 00 00 00 00 55 <48> 8b 0f 49 89 f8 48 89 e5 48 89 ca 48 c1 ea 36 0f a3 15 d8 2f
> [ 372.415032] RIP [<ffffffff81117ed1>] is_pageblock_removable_nolock+0x1/0x90
> [ 372.422905] RSP <ffff880820023df8>
> [ 372.426792] CR2: ffffea00c3200000
> ---------------------------------------------------------
>
>
> ---
> drivers/base/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux/drivers/base/memory.c
> ===================================================================
> --- linux.orig/drivers/base/memory.c 2013-08-22 21:16:03.477826999 -0500
> +++ linux/drivers/base/memory.c 2013-08-22 21:22:38.885478035 -0500
> @@ -140,7 +140,7 @@ static ssize_t show_mem_removable(struct
> struct memory_block *mem =
> container_of(dev, struct memory_block, dev);
>
> - for (i = 0; i < sections_per_block; i++) {
> + for (i = 0; i < mem->section_count; i++) {
I don't think it works well.
mem->section_count means how many present section is in the memory_block.
If 0, 1, 3 and 4 sections are present in the memory_block, mem->section_count
is 4. In this case, is_mem_sectionremovable is called for section 2. But the
section is not present. So if the memory_block has hole, same problem will occur.
How about keep sections_per_block loop and add following check:
if (!present_section_nr(mem->start_section_nr + i))
continue;
Thanks,
Yasuaki Ishimatsu
> pfn = section_nr_to_pfn(mem->start_section_nr + i);
> ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
> }
>
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