On 2018/9/4 上午4:24, Christoph Anton Mitterer wrote:
> Hey.
>
>
> On Fri, 2018-08-31 at 10:33 +0800, Su Yue wrote:
>> Can you please fetch btrfs-progs from my repo and run lowmem check
>> in readonly?
>> Repo: https://github.com/Damenly/btrfs-progs/tree/lowmem_debug
>> It's based on v4.17.1 plus additonal output for debug only.
>
> I've adapted your patch to 4.17 from Debian (i.e. not the 4.17.1).
>
>
> First I ran it again with the pristine 4.17 from Debian:
> # btrfs check --mode=lowmem /dev/mapper/system ; echo $?
> Checking filesystem on /dev/mapper/system
> UUID: 6050ca10-e778-4d08-80e7-6d27b9c89b3c
> checking extents
> checking free space cache
> checking fs roots
> ERROR: errors found in fs roots
> found 435924422656 bytes used, error(s) found
> total csum bytes: 423418948
> total tree bytes: 2218328064
> total fs tree bytes: 1557168128
> total extent tree bytes: 125894656
> btree space waste bytes: 429599230
> file data blocks allocated: 5193373646848
> referenced 555255164928
> [ 1248.687628] ------------[ cut here ]------------
> [ 1248.688352] generic_make_request: Trying to write to read-only
> block-device dm-0 (partno 0)
> [ 1248.689127] WARNING: CPU: 3 PID: 933 at
> /build/linux-LgHyGB/linux-4.17.17/block/blk-core.c:2180
> generic_make_request_checks+0x43d/0x610
> [ 1248.689909] Modules linked in: dm_crypt algif_skcipher af_alg dm_mod
> snd_hda_codec_hdmi snd_hda_codec_realtek intel_rapl snd_hda_codec_generic
> x86_pkg_temp_thermal intel_powerclamp i915 iwlwifi btusb coretemp btrtl btbcm
> uvcvideo kvm_intel snd_hda_intel btintel videobuf2_vmalloc bluetooth
> snd_hda_codec kvm videobuf2_memops videobuf2_v4l2 videobuf2_common cfg80211
> snd_hda_core irqbypass videodev jitterentropy_rng drm_kms_helper
> crct10dif_pclmul snd_hwdep crc32_pclmul drbg ghash_clmulni_intel intel_cstate
> snd_pcm ansi_cprng ppdev intel_uncore drm media ecdh_generic iTCO_wdt
> snd_timer iTCO_vendor_support rtsx_pci_ms crc16 snd intel_rapl_perf memstick
> joydev mei_me rfkill evdev soundcore sg parport_pc pcspkr serio_raw
> fujitsu_laptop mei i2c_algo_bit parport shpchp sparse_keymap pcc_cpufreq
> lpc_ich button
> [ 1248.693639] video battery ac ip_tables x_tables autofs4 btrfs
> zstd_decompress zstd_compress xxhash raid10 raid456 async_raid6_recov
> async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
> crc32c_generic raid1 raid0 multipath linear md_mod sd_mod uas usb_storage
> crc32c_intel rtsx_pci_sdmmc mmc_core ahci xhci_pci libahci aesni_intel
> ehci_pci aes_x86_64 libata crypto_simd xhci_hcd ehci_hcd cryptd glue_helper
> psmouse i2c_i801 scsi_mod rtsx_pci e1000e usbcore usb_common
> [ 1248.696956] CPU: 3 PID: 933 Comm: btrfs Not tainted 4.17.0-3-amd64 #1
> Debian 4.17.17-1
> [ 1248.698118] Hardware name: FUJITSU LIFEBOOK E782/FJNB253, BIOS Version
> 2.11 07/15/2014
> [ 1248.699299] RIP: 0010:generic_make_request_checks+0x43d/0x610
> [ 1248.700495] RSP: 0018:ffffac89827c7d88 EFLAGS: 00010286
> [ 1248.701702] RAX: 0000000000000000 RBX: ffff98f4848a9200 RCX:
> 0000000000000006
> [ 1248.702930] RDX: 0000000000000007 RSI: 0000000000000082 RDI:
> ffff98f49e2d6730
> [ 1248.704170] RBP: ffff98f484f6d460 R08: 000000000000033e R09:
> 0000000000aaaaaa
> [ 1248.705422] R10: ffffac89827c7e60 R11: 00000000ffffffff R12:
> 0000000000000000
> [ 1248.706675] R13: 0000000000000001 R14: 0000000000000000 R15:
> 0000000000000000
> [ 1248.707928] FS: 00007f92842018c0(0000) GS:ffff98f49e2c0000(0000)
> knlGS:0000000000000000
> [ 1248.709190] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 1248.710448] CR2: 000055fc6fe1a5b0 CR3: 0000000407f62001 CR4:
> 00000000001606e0
> [ 1248.711707] Call Trace:
> [ 1248.712960] ? do_writepages+0x4b/0xe0
> [ 1248.714201] ? blkdev_readpages+0x20/0x20
> [ 1248.715441] ? do_writepages+0x4b/0xe0
> [ 1248.716684] generic_make_request+0x64/0x400
> [ 1248.717935] ? finish_wait+0x80/0x80
> [ 1248.719181] ? mempool_alloc+0x67/0x1a0
> [ 1248.720425] ? submit_bio+0x6c/0x140
> [ 1248.721663] submit_bio+0x6c/0x140
> [ 1248.722902] submit_bio_wait+0x53/0x80
> [ 1248.724139] blkdev_issue_flush+0x7c/0xb0
> [ 1248.725377] blkdev_fsync+0x2f/0x40
> [ 1248.726612] do_fsync+0x38/0x60
> [ 1248.727849] __x64_sys_fsync+0x10/0x20
> [ 1248.729086] do_syscall_64+0x55/0x110
> [ 1248.730323] entry_SYSCALL_64_after_hwframe+0x44/0xa9
I don't really think it's "btrfs check" causing the problem.
Btrfs check, just like all offline tools, uses open_ctree_flags to
determine if it's allowed to do write.
Without OPEN_CTREE_FLAGS_WRITE, all devices are opened RO, thus any
write will just return error without reaching disk.
Not to mention such fsync syscall.
However the backtrace can't tell which process caused such fsync call.
(Maybe LVM user space code?)
Thanks,
Qu
> [ 1248.731565] RIP: 0033:0x7f928354d161
> [ 1248.732805] RSP: 002b:00007ffd35e3f5d8 EFLAGS: 00000246 ORIG_RAX:
> 000000000000004a
> [ 1248.734067] RAX: ffffffffffffffda RBX: 000055fc09c0c260 RCX:
> 00007f928354d161
> [ 1248.735342] RDX: 000055fc09c13e28 RSI: 000055fc0899f820 RDI:
> 0000000000000004
> [ 1248.736614] RBP: 000055fc09c0c2d0 R08: 0000000000000005 R09:
> 000055fc09c0da70
> [ 1248.738001] R10: 000000000000009e R11: 0000000000000246 R12:
> 0000000000000000
> [ 1248.739272] R13: 000055fc0899d213 R14: 000055fc09c0c290 R15:
> 0000000000000001
> [ 1248.740542] Code: 24 54 03 00 00 48 8d 74 24 08 48 89 df c6 05 3e 03 d9 00
> 01 e8 d5 63 01 00 44 89 e2 48 89 c6 48 c7 c7 80 e1 e6 ad e8 a3 4e d1 ff <0f>
> 0b 4c 8b 63 08 e9 7b fc ff ff 80 3d 15 03 d9 00 00 0f 85 94
> [ 1248.741909] ---[ end trace c2f580dbd579028c ]---
> 1
>
> Not really sure why btrfs-check apparently tries to write to the device
> (I've had set it blockdev --setro).
>
>
>
> And with your patch:
> # btrfs check --mode=lowmem /dev/mapper/system ; echo $?
> checking extents
> checking free space cache
> checking fs roots
> ERROR: errors found in fs roots
> Checking filesystem on /dev/mapper/system
> UUID: 6050ca10-e778-4d08-80e7-6d27b9c89b3c
> DEBUG: error before walking while checking fs root 3 ret -694376768
> DEBUG: normal error in walking while checking node 125988438016 fs root
> 257 ret 524296
> DEBUG: error in checking fs root 257 ret 524296
> DEBUG: normal error in walking while checking node 230148259840 fs root
> 743 ret 524296
> DEBUG: error in checking fs root 743 ret 524296
> DEBUG: error in checking fs roots ret:
> found 435924422656 bytes used, error(s) found
> total csum bytes: 423418948
> total tree bytes: 2218328064
> total fs tree bytes: 1557168128
> total extent tree bytes: 125894656
> btree space waste bytes: 429599230
> file data blocks allocated: 5193373646848
> referenced 555255164928
> 1
>
> Interestingly it doesn't try to write again (or the kernel doesn't just
> print another call trace this time).
>
>
>
> Cheers,
> Chris.
>
