BUG: unable to handle kernel NULL pointer dereference

BUG: unable to handle kernel NULL pointer dereference

[matthieu Barthélemy]

Hi all,

I have a Btrfs partition that cannot be mounted anymore, it makes
kernel to crash.
The partition was created a few months ago, with kernel 2.6.33 (with
no special options) if I remember well. Since then, with new kernel
releases, I enabled a few options : first space_cache, then compress,
and finally with 2.6.38 compress=lzo
So the filesystem has now space_cache, data compressed with zlib AND lzo.

With kernel 2.6.39-rc5 I had, a few weeks ago, a first crash where it
complained about no free space. Then I rebooted on kernel 2.6.38,
mounted the filesystem with the clear_cache option, and everything
went fine, even returning back on kernel 2.6.39-rc5.

But last week, while I was working (nothing special such as intensive
read or writes), the system crashed because of Btrfs.
Since then, I cannot mount my FS anymore.
Here are the dmesg logs I gathered, testing with 2.6.39-rc5, and just
to see if it made any difference, with the integration-test tree.

Any idea about what happened? How can I help you to diagnose that? Any
chance I could recover my data?

Thanks.

with 2.6.39-rc5 :
# mount -o clear_cache,compress=lzo /dev/sda2 /mnt/

[  676.767161] Btrfs loaded
[  676.774399] device fsid f24027efc24d32f7-2191b1da9df7d184 devid 1
transid 164511 /dev/sda2
[  676.775233] btrfs: force clearing of disk cache
[  676.775255] btrfs: use lzo compression
[  676.834811] btrfs: disk space caching is enabled
[  677.601773] BUG: unable to handle kernel NULL pointer dereference at   (null)
[  677.601800] IP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0
[  677.601822] *pde = 00000000
[  677.601834] Oops: 0000 [#1] SMP
[  677.601846] last sysfs file: /sys/devices/virtual/bdi/btrfs-1/uevent
[  677.601861] Modules linked in: btrfs zlib_deflate af_packet
snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel btusb
snd_hda_codec bluetooth usb_storage snd_hwdep uas iTCO_wdt
iTCO_vendor_support snd_pcm rfkill r8187se(C) uvcvideo videodev
snd_timer media joydev wmi battery ac sg eeprom_93cx6 snd pcspkr
soundcore r8169 snd_page_alloc ext4 jbd2 crc16 usbhid hid sd_mod
ata_generic i915 ata_piix drm_kms_helper libata drm uhci_hcd scsi_mod
ehci_hcd i2c_algo_bit rtc_cmos rtc_core rtc_lib usbcore intel_agp
button video intel_gtt fan thermal processor thermal_sys hwmon
[  677.602034]
[  677.602046] Pid: 2401, comm: mount Tainted: G         C
2.6.39-rc5-0.3-default #6 LG Electronics X110-L.A741B/X110
[  677.602068] EIP: 0060:[<c022bbfb>] EFLAGS: 00210202 CPU: 1
[  677.602082] EIP is at kmap_atomic_prot+0x1b/0xf0
[  677.602094] EAX: 00000000 EBX: 000004ca ECX: d9fee000 EDX: 00000163
[  677.602107] ESI: 00000000 EDI: 000004ca EBP: d9fefb88 ESP: d9fefb78
[  677.602121]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[  677.602134] Process mount (pid: 2401, ti=d9fee000 task=e61bf030
task.ti=d9fee000)
[  677.602147] Stack:
[  677.602156]  f64037c0 000004ca 00000000 000004ca d9fefb90 c022bcde
d9fefbbc f853bab8
[  677.602179]  00000000 c71c40f0 c68560a8 00000007 b7c09000 0000000e
00006572 c6850000
[  677.602202]  00000f58 d9fefc24 f854b727 00006572 00000000 00000000
00000000 00094689
[  677.602225] Call Trace:
[  677.602239]  [<c022bcde>] __kmap_atomic+0xe/0x10
[  677.602281]  [<f853bab8>] read_extent_buffer+0x88/0x140 [btrfs]
[  677.602322]  [<f854b727>] add_inode_ref+0x1e7/0x330 [btrfs]
[  677.602363]  [<f854ccde>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  677.602404]  [<f854a431>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  677.602445]  [<f854a636>] walk_log_tree+0x76/0x1e0 [btrfs]
[  677.602463]  [<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
[  677.602503]  [<f854e8fe>] btrfs_recover_log_trees+0x1de/0x2b0 [btrfs]
[  677.602544]  [<f854cac0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  677.602596]  [<f8513a8c>] open_ctree+0x10bc/0x1410 [btrfs]
[  677.602615]  [<c03e9ca9>] ? strlcpy+0x39/0x60
[  677.602646]  [<f84f45e1>] btrfs_mount+0x461/0x590 [btrfs]
[  677.602664]  [<c02e3400>] ? pcpu_alloc+0x310/0x850
[  677.602681]  [<c03098d5>] mount_fs+0x35/0x180
[  677.602698]  [<c031e9d6>] vfs_kern_mount+0x46/0xa0
[  677.602712]  [<c031f7c9>] do_kern_mount+0x39/0xd0
[  677.602726]  [<c0320f34>] do_mount+0x594/0x6c0
[  677.602741]  [<c02d13d6>] ? __get_free_pages+0x26/0x30
[  677.602755]  [<c0320879>] ? copy_mount_options+0x39/0x120
[  677.602770]  [<c0321386>] sys_mount+0x66/0xa0
[  677.602786]  [<c05d021c>] sysenter_do_call+0x12/0x28
[  677.602798] Code: 8b 15 cc 42 82 c0 55 89 e5 e8 52 f9 ff ff 5d c3
55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 db 78 c0 2b b1
cc de
[  677.602902] EIP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0 SS:ESP 0068:d9fefb78
[  677.602920] CR2: 0000000000000000
[  677.604805] [drm] Changing LVDS panel from (+hsync, +vsync) to
(-hsync, -vsync)
[  677.854425] ---[ end trace b216833b014671c4 ]---
[  677.854452] note: mount[2401] exited with preempt_count 1
[  677.854731] BUG: scheduling while atomic: mount/2401/0x10000001
[  677.854753] Modules linked in: btrfs zlib_deflate af_packet
snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel btusb
snd_hda_codec bluetooth usb_storage snd_hwdep uas iTCO_wdt
iTCO_vendor_support snd_pcm rfkill r8187se(C) uvcvideo videodev
snd_timer media joydev wmi battery ac sg eeprom_93cx6 snd pcspkr
soundcore r8169 snd_page_alloc ext4 jbd2 crc16 usbhid hid sd_mod
ata_generic i915 ata_piix drm_kms_helper libata drm uhci_hcd scsi_mod
ehci_hcd i2c_algo_bit rtc_cmos rtc_core rtc_lib usbcore intel_agp
button video intel_gtt fan thermal processor thermal_sys hwmon
[  677.854935] Pid: 2401, comm: mount Tainted: G      D  C
2.6.39-rc5-0.3-default #6
[  677.854942] Call Trace:
[  677.854959]  [<c023420d>] __schedule_bug+0x5d/0x70
[  677.854971]  [<c05c7984>] schedule+0xa24/0xa30
[  677.854982]  [<c02d4310>] ? release_pages+0x1b0/0x1e0
[  677.854993]  [<c030838f>] ? fput+0x12f/0x1e0
[  677.855004]  [<c02ea9ca>] ? remove_vma+0x3a/0x50
[  677.855015]  [<c023f846>] __cond_resched+0x16/0x30
[  677.855024]  [<c05c7ba3>] _cond_resched+0x23/0x30
[  677.855034]  [<c0248cdc>] put_files_struct+0x6c/0xb0
[  677.855043]  [<c0248dac>] exit_files+0x3c/0x50
[  677.855051]  [<c02491de>] do_exit+0x15e/0x780
[  677.855060]  [<c0247227>] ? kmsg_dump+0x37/0xd0
[  677.855070]  [<c05c6c6d>] ? printk+0x28/0x2b
[  677.855080]  [<c05cad9d>] oops_end+0x8d/0xd0
[  677.855090]  [<c022700e>] no_context+0xbe/0x150
[  677.855100]  [<c0227227>] __bad_area_nosemaphore+0x37/0x170
[  677.855111]  [<c0227372>] bad_area_nosemaphore+0x12/0x20
[  677.855121]  [<c05ccc94>] do_page_fault+0x2c4/0x420
[  677.855131]  [<c02d0dbe>] ? __alloc_pages_nodemask+0xee/0x6e0
[  677.855142]  [<c022bc27>] ? kmap_atomic_prot+0x47/0xf0
[  677.855152]  [<c05cc9d0>] ? spurious_fault+0xd0/0xd0
[  677.855161]  [<c05ca34a>] error_code+0x5a/0x60
[  677.855171]  [<c05cc9d0>] ? spurious_fault+0xd0/0xd0
[  677.855180]  [<c022bbfb>] ? kmap_atomic_prot+0x1b/0xf0
[  677.855189]  [<c022bcde>] __kmap_atomic+0xe/0x10
[  677.855235]  [<f853bab8>] read_extent_buffer+0x88/0x140 [btrfs]
[  677.855273]  [<f854b727>] add_inode_ref+0x1e7/0x330 [btrfs]
[  677.855318]  [<f854ccde>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  677.855358]  [<f854a431>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  677.855399]  [<f854a636>] walk_log_tree+0x76/0x1e0 [btrfs]
[  677.855410]  [<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
[  677.855446]  [<f854e8fe>] btrfs_recover_log_trees+0x1de/0x2b0 [btrfs]
[  677.855488]  [<f854cac0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  677.855539]  [<f8513a8c>] open_ctree+0x10bc/0x1410 [btrfs]
[  677.855552]  [<c03e9ca9>] ? strlcpy+0x39/0x60
[  677.855583]  [<f84f45e1>] btrfs_mount+0x461/0x590 [btrfs]
[  677.855594]  [<c02e3400>] ? pcpu_alloc+0x310/0x850
[  677.855604]  [<c03098d5>] mount_fs+0x35/0x180
[  677.855616]  [<c031e9d6>] vfs_kern_mount+0x46/0xa0
[  677.855625]  [<c031f7c9>] do_kern_mount+0x39/0xd0
[  677.855634]  [<c0320f34>] do_mount+0x594/0x6c0
[  677.855643]  [<c02d13d6>] ? __get_free_pages+0x26/0x30
[  677.855652]  [<c0320879>] ? copy_mount_options+0x39/0x120
[  677.855661]  [<c0321386>] sys_mount+0x66/0xa0
[  677.855672]  [<c05d021c>] sysenter_do_call+0x12/0x28




with 2.6.39-rc5, without clear_cache option
 # mount -o compress=lzo /dev/sda2 /mnt/
[  138.393711] Btrfs loaded
[  138.415758] device fsid f24027efc24d32f7-2191b1da9df7d184 devid 1
transid 164511 /dev/sda2
[  138.416404] btrfs: use lzo compression
[  138.476160] btrfs: disk space caching is enabled
[  139.154606] block group 29360128 has an wrong amount of free space
[  139.287457] BUG: unable to handle kernel NULL pointer dereference at   (null)
[  139.287484] IP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0
[  139.287506] *pde = 00000000
[  139.287518] Oops: 0000 [#1] SMP
[  139.287530] last sysfs file: /sys/devices/virtual/bdi/btrfs-1/uevent
[  139.287544] Modules linked in: btrfs zlib_deflate af_packet
snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
snd_hda_codec snd_hwdep snd_pcm usb_storage uas snd_timer uvcvideo
videodev iTCO_wdt iTCO_vendor_support snd soundcore snd_page_alloc
media btusb pcspkr bluetooth r8187se(C) rfkill joydev battery r8169
eeprom_93cx6 wmi sg ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
i915 drm_kms_helper ata_piix drm uhci_hcd rtc_cmos rtc_core libata
ehci_hcd i2c_algo_bit rtc_lib usbcore scsi_mod button intel_agp
intel_gtt video fan thermal processor thermal_sys hwmon
[  139.287717]
[  139.287729] Pid: 2193, comm: mount Tainted: G         C
2.6.39-rc5-0.3-default #6 LG Electronics X110-L.A741B/X110
[  139.287751] EIP: 0060:[<c022bbfb>] EFLAGS: 00210202 CPU: 1
[  139.287764] EIP is at kmap_atomic_prot+0x1b/0xf0
[  139.287777] EAX: 00000000 EBX: 000004ca ECX: cccc2000 EDX: 00000163
[  139.287790] ESI: 00000000 EDI: 000004ca EBP: cccc3b88 ESP: cccc3b78
[  139.287804]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[  139.287817] Process mount (pid: 2193, ti=cccc2000 task=ccc90d30
task.ti=cccc2000)
[  139.287830] Stack:
[  139.287838]  f64037c0 000004ca 00000000 000004ca cccc3b90 c022bcde
cccc3bbc f8935ab8
[  139.287861]  00000000 d0570180 c92ce0a8 00000007 b7c09000 0000000e
00006572 c92c8000
[  139.287884]  00000f58 cccc3c24 f8945727 00006572 00000000 00000000
00000000 00094689
[  139.287907] Call Trace:
[  139.287921]  [<c022bcde>] __kmap_atomic+0xe/0x10
[  139.287963]  [<f8935ab8>] read_extent_buffer+0x88/0x140 [btrfs]
[  139.288005]  [<f8945727>] add_inode_ref+0x1e7/0x330 [btrfs]
[  139.288056]  [<f8946cde>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  139.288098]  [<f8944431>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  139.288139]  [<f8944636>] walk_log_tree+0x76/0x1e0 [btrfs]
[  139.288157]  [<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
[  139.288197]  [<f89488fe>] btrfs_recover_log_trees+0x1de/0x2b0 [btrfs]
[  139.288238]  [<f8946ac0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  139.288290]  [<f890da8c>] open_ctree+0x10bc/0x1410 [btrfs]
[  139.288310]  [<c03e9ca9>] ? strlcpy+0x39/0x60
[  139.288341]  [<f88ee5e1>] btrfs_mount+0x461/0x590 [btrfs]
[  139.288359]  [<c02e3400>] ? pcpu_alloc+0x310/0x850
[  139.288375]  [<c03098d5>] mount_fs+0x35/0x180
[  139.288392]  [<c031e9d6>] vfs_kern_mount+0x46/0xa0
[  139.288407]  [<c031f7c9>] do_kern_mount+0x39/0xd0
[  139.288421]  [<c0320f34>] do_mount+0x594/0x6c0
[  139.288436]  [<c02d13d6>] ? __get_free_pages+0x26/0x30
[  139.288450]  [<c0320879>] ? copy_mount_options+0x39/0x120
[  139.288464]  [<c0321386>] sys_mount+0x66/0xa0
[  139.288481]  [<c05d021c>] sysenter_do_call+0x12/0x28
[  139.288493] Code: 8b 15 cc 42 82 c0 55 89 e5 e8 52 f9 ff ff 5d c3
55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 db 78 c0 2b b1
cc de
[  139.288595] EIP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0 SS:ESP 0068:cccc3b78
[  139.288614] CR2: 0000000000000000
[  139.310232] ---[ end trace 34b5224bc0e9db2d ]---
[  139.310259] note: mount[2193] exited with preempt_count 1
[  139.310531] BUG: scheduling while atomic: mount/2193/0x10000001
[  139.310553] Modules linked in: btrfs zlib_deflate af_packet
snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
snd_hda_codec snd_hwdep snd_pcm usb_storage uas snd_timer uvcvideo
videodev iTCO_wdt iTCO_vendor_support snd soundcore snd_page_alloc
media btusb pcspkr bluetooth r8187se(C) rfkill joydev battery r8169
eeprom_93cx6 wmi sg ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
i915 drm_kms_helper ata_piix drm uhci_hcd rtc_cmos rtc_core libata
ehci_hcd i2c_algo_bit rtc_lib usbcore scsi_mod button intel_agp
intel_gtt video fan thermal processor thermal_sys hwmon
[  139.310856] Pid: 2193, comm: mount Tainted: G      D  C
2.6.39-rc5-0.3-default #6
[  139.310881] Call Trace:
[  139.310911]  [<c023420d>] __schedule_bug+0x5d/0x70
[  139.310940]  [<c05c7984>] schedule+0xa24/0xa30
[  139.310967]  [<c02d4310>] ? release_pages+0x1b0/0x1e0
[  139.310995]  [<c030838f>] ? fput+0x12f/0x1e0
[  139.311022]  [<c02ea9ca>] ? remove_vma+0x3a/0x50
[  139.311048]  [<c023f846>] __cond_resched+0x16/0x30
[  139.311075]  [<c05c7ba3>] _cond_resched+0x23/0x30
[  139.311100]  [<c0248cdc>] put_files_struct+0x6c/0xb0
[  139.311126]  [<c0248dac>] exit_files+0x3c/0x50
[  139.311147]  [<c02491de>] do_exit+0x15e/0x780
[  139.311168]  [<c0247227>] ? kmsg_dump+0x37/0xd0
[  139.311189]  [<c05c6c6d>] ? printk+0x28/0x2b
[  139.311211]  [<c05cad9d>] oops_end+0x8d/0xd0
[  139.311233]  [<c022700e>] no_context+0xbe/0x150
[  139.311255]  [<c0227227>] __bad_area_nosemaphore+0x37/0x170
[  139.311279]  [<c0227372>] bad_area_nosemaphore+0x12/0x20
[  139.311301]  [<c05ccc94>] do_page_fault+0x2c4/0x420
[  139.311323]  [<c02d0dbe>] ? __alloc_pages_nodemask+0xee/0x6e0
[  139.311347]  [<c022bc27>] ? kmap_atomic_prot+0x47/0xf0
[  139.311373]  [<c05cc9d0>] ? spurious_fault+0xd0/0xd0
[  139.311398]  [<c05ca34a>] error_code+0x5a/0x60
[  139.311423]  [<c05cc9d0>] ? spurious_fault+0xd0/0xd0
[  139.311450]  [<c022bbfb>] ? kmap_atomic_prot+0x1b/0xf0
[  139.311476]  [<c022bcde>] __kmap_atomic+0xe/0x10
[  139.311537]  [<f8935ab8>] read_extent_buffer+0x88/0x140 [btrfs]
[  139.311598]  [<f8945727>] add_inode_ref+0x1e7/0x330 [btrfs]
[  139.311657]  [<f8946cde>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  139.311710]  [<f8944431>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  139.311761]  [<f8944636>] walk_log_tree+0x76/0x1e0 [btrfs]
[  139.311786]  [<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
[  139.311846]  [<f89488fe>] btrfs_recover_log_trees+0x1de/0x2b0 [btrfs]
[  139.311907]  [<f8946ac0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  139.311980]  [<f890da8c>] open_ctree+0x10bc/0x1410 [btrfs]
[  139.312038]  [<c03e9ca9>] ? strlcpy+0x39/0x60
[  139.312087]  [<f88ee5e1>] btrfs_mount+0x461/0x590 [btrfs]
[  139.312115]  [<c02e3400>] ? pcpu_alloc+0x310/0x850
[  139.312142]  [<c03098d5>] mount_fs+0x35/0x180
[  139.312171]  [<c031e9d6>] vfs_kern_mount+0x46/0xa0
[  139.312198]  [<c031f7c9>] do_kern_mount+0x39/0xd0
[  139.312223]  [<c0320f34>] do_mount+0x594/0x6c0
[  139.312249]  [<c02d13d6>] ? __get_free_pages+0x26/0x30
[  139.312275]  [<c0320879>] ? copy_mount_options+0x39/0x120
[  139.312302]  [<c0321386>] sys_mount+0x66/0xa0
[  139.312328]  [<c05d021c>] sysenter_do_call+0x12/0x28



with integration-test tree (2011/05/24)
# mount -o clear_cache,compress=lzo /dev/sda2 /mnt/
[  295.895116] Btrfs loaded
[  295.906626] device fsid f24027efc24d32f7-2191b1da9df7d184 devid 1
transid 164511 /dev/sda2
[  295.907432] btrfs: force clearing of disk cache
[  295.907455] btrfs: use lzo compression
[  295.967015] btrfs: disk space caching is enabled
[  296.767248] BUG: unable to handle kernel NULL pointer dereference at   (null)
[  296.767274] IP: [<c022bcab>] kmap_atomic_prot+0x1b/0xf0
[  296.767298] *pde = 00000000
[  296.767310] Oops: 0000 [#1] SMP
[  296.767322] last sysfs file:
/sys/devices/LNXSYSTM:00/device:00/PNP0A08:00/device:11/PNP0C09:00/PNP0C0A:00/power_supply/BAT1/voltage_now
[  296.767346] Modules linked in: btrfs zlib_deflate fuse af_packet
snd_pcm_oss snd_mixer_oss snd_seq bnep snd_seq_device edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
snd_hda_codec snd_hwdep snd_pcm snd_timer snd uvcvideo r8187se(C)
btusb videodev soundcore usb_storage iTCO_wdt sg iTCO_vendor_support
uas eeprom_93cx6 bluetooth r8169 wmi media rfkill snd_page_alloc
joydev pcspkr battery ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
i915 drm_kms_helper uhci_hcd ata_piix drm ehci_hcd libata scsi_mod
rtc_cmos intel_agp i2c_algo_bit usbcore intel_gtt rtc_core rtc_lib
video button fan thermal processor thermal_sys hwmon
[  296.767523]
[  296.767534] Pid: 2299, comm: mount Tainted: G         C
2.6.39-0.3-default+ #1 LG Electronics X110-L.A741B/X110
[  296.767556] EIP: 0060:[<c022bcab>] EFLAGS: 00210202 CPU: 1
[  296.767570] EIP is at kmap_atomic_prot+0x1b/0xf0
[  296.767582] EAX: 00000000 EBX: 000004ca ECX: d6c4e000 EDX: 00000163
[  296.767595] ESI: 00000000 EDI: 000004ca EBP: d6c4fb78 ESP: d6c4fb68
[  296.767609]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[  296.767623] Process mount (pid: 2299, ti=d6c4e000 task=d6c4ce70
task.ti=d6c4e000)
[  296.767636] Stack:
[  296.767644]  f4c037c0 000004ca 00000000 000004ca d6c4fb80 c022bd8e
d6c4fbac f888a278
[  296.767667]  00000000 e1ac3888 f400e0a8 00000007 b7c09000 0000000e
00006572 f4008000
[  296.767690]  00000f58 d6c4fc20 f8899e5f 00006572 00000000 00000000
00000000 00094689
[  296.767713] Call Trace:
[  296.767727]  [<c022bd8e>] __kmap_atomic+0xe/0x10
[  296.767770]  [<f888a278>] read_extent_buffer+0x88/0x140 [btrfs]
[  296.767812]  [<f8899e5f>] add_inode_ref+0x22f/0x370 [btrfs]
[  296.767854]  [<f889b7fe>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  296.767897]  [<f8898e61>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  296.767939]  [<f8899066>] walk_log_tree+0x76/0x1e0 [btrfs]
[  296.767957]  [<c03e585a>] ? radix_tree_lookup+0xa/0x10
[  296.767998]  [<f889d47c>] btrfs_recover_log_trees+0x1dc/0x2a0 [btrfs]
[  296.768050]  [<f889b5e0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  296.768104]  [<f88624c5>] open_ctree+0x11c5/0x1510 [btrfs]
[  296.768124]  [<c03e7ad9>] ? strlcpy+0x39/0x60
[  296.768155]  [<f8842651>] btrfs_mount+0x461/0x590 [btrfs]
[  296.768174]  [<c02e2300>] ? pcpu_alloc+0x2c0/0x850
[  296.768192]  [<c0307f25>] mount_fs+0x35/0x180
[  296.768208]  [<c031cfe6>] vfs_kern_mount+0x46/0xa0
[  296.768223]  [<c031ddd9>] do_kern_mount+0x39/0xd0
[  296.768237]  [<c031f544>] do_mount+0x594/0x6c0
[  296.768253]  [<c02d02a6>] ? __get_free_pages+0x26/0x30
[  296.768268]  [<c031ee89>] ? copy_mount_options+0x39/0x120
[  296.768282]  [<c031f996>] sys_mount+0x66/0xa0
[  296.768298]  [<c05b745c>] sysenter_do_call+0x12/0x28
[  296.768310] Code: 8b 15 cc f2 7f c0 55 89 e5 e8 52 f9 ff ff 5d c3
55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 a8 76 c0 2b b1
cc ab
[  296.768413] EIP: [<c022bcab>] kmap_atomic_prot+0x1b/0xf0 SS:ESP 0068:d6c4fb68
[  296.768432] CR2: 0000000000000000
[  296.770367] [drm] Changing LVDS panel from (+hsync, +vsync) to
(-hsync, -vsync)
[  296.949992] ---[ end trace 0963ef50bd4dfa03 ]---
[  296.950017] note: mount[2299] exited with preempt_count 1
[  296.950322] BUG: scheduling while atomic: mount/2299/0x10000001
[  296.950345] Modules linked in: btrfs zlib_deflate fuse af_packet
snd_pcm_oss snd_mixer_oss snd_seq bnep snd_seq_device edd
cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
snd_hda_codec snd_hwdep snd_pcm snd_timer snd uvcvideo r8187se(C)
btusb videodev soundcore usb_storage iTCO_wdt sg iTCO_vendor_support
uas eeprom_93cx6 bluetooth r8169 wmi media rfkill snd_page_alloc
joydev pcspkr battery ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
i915 drm_kms_helper uhci_hcd ata_piix drm ehci_hcd libata scsi_mod
rtc_cmos intel_agp i2c_algo_bit usbcore intel_gtt rtc_core rtc_lib
video button fan thermal processor thermal_sys hwmon
[  296.950537] Pid: 2299, comm: mount Tainted: G      D  C
2.6.39-0.3-default+ #1
[  296.950543] Call Trace:
[  296.950561]  [<c023438d>] __schedule_bug+0x5d/0x70
[  296.950573]  [<c05aea3d>] schedule+0x8cd/0xa60
[  296.950584]  [<c02d3280>] ? release_pages+0x1b0/0x1e0
[  296.950597]  [<c03069df>] ? fput+0x12f/0x1e0
[  296.950608]  [<c02e983a>] ? remove_vma+0x3a/0x50
[  296.950619]  [<c023f886>] __cond_resched+0x16/0x30
[  296.950628]  [<c05aede3>] _cond_resched+0x23/0x30
[  296.950637]  [<c0248cdc>] put_files_struct+0x6c/0xb0
[  296.950646]  [<c0248dac>] exit_files+0x3c/0x50
[  296.950655]  [<c02491de>] do_exit+0x15e/0x780
[  296.950664]  [<c0247227>] ? kmsg_dump+0x37/0xd0
[  296.950673]  [<c05ade7d>] ? printk+0x28/0x2b
[  296.950684]  [<c05b1fdd>] oops_end+0x8d/0xd0
[  296.950694]  [<c02270be>] no_context+0xbe/0x150
[  296.950704]  [<c02272d7>] __bad_area_nosemaphore+0x37/0x170
[  296.950714]  [<c0227422>] bad_area_nosemaphore+0x12/0x20
[  296.950724]  [<c05b3ed4>] do_page_fault+0x2c4/0x420
[  296.950735]  [<c02cfc8e>] ? __alloc_pages_nodemask+0xee/0x6e0
[  296.950746]  [<c022bcd7>] ? kmap_atomic_prot+0x47/0xf0
[  296.950757]  [<c05b3c10>] ? spurious_fault+0xd0/0xd0
[  296.950766]  [<c05b158a>] error_code+0x5a/0x60
[  296.950776]  [<c05b3c10>] ? spurious_fault+0xd0/0xd0
[  296.950785]  [<c022bcab>] ? kmap_atomic_prot+0x1b/0xf0
[  296.950794]  [<c022bd8e>] __kmap_atomic+0xe/0x10
[  296.950841]  [<f888a278>] read_extent_buffer+0x88/0x140 [btrfs]
[  296.950886]  [<f8899e5f>] add_inode_ref+0x22f/0x370 [btrfs]
[  296.950927]  [<f889b7fe>] replay_one_buffer+0x21e/0x2e0 [btrfs]
[  296.950972]  [<f8898e61>] walk_down_log_tree+0x1d1/0x360 [btrfs]
[  296.951012]  [<f8899066>] walk_log_tree+0x76/0x1e0 [btrfs]
[  296.951023]  [<c03e585a>] ? radix_tree_lookup+0xa/0x10
[  296.951064]  [<f889d47c>] btrfs_recover_log_trees+0x1dc/0x2a0 [btrfs]
[  296.951104]  [<f889b5e0>] ? replay_one_extent+0x6a0/0x6a0 [btrfs]
[  296.951156]  [<f88624c5>] open_ctree+0x11c5/0x1510 [btrfs]
[  296.951168]  [<c03e7ad9>] ? strlcpy+0x39/0x60
[  296.951198]  [<f8842651>] btrfs_mount+0x461/0x590 [btrfs]
[  296.951209]  [<c02e2300>] ? pcpu_alloc+0x2c0/0x850
[  296.951221]  [<c0307f25>] mount_fs+0x35/0x180
[  296.951232]  [<c031cfe6>] vfs_kern_mount+0x46/0xa0
[  296.951242]  [<c031ddd9>] do_kern_mount+0x39/0xd0
[  296.951251]  [<c031f544>] do_mount+0x594/0x6c0
[  296.951261]  [<c02d02a6>] ? __get_free_pages+0x26/0x30
[  296.951270]  [<c031ee89>] ? copy_mount_options+0x39/0x120
[  296.951279]  [<c031f996>] sys_mount+0x66/0xa0
[  296.951289]  [<c05b745c>] sysenter_do_call+0x12/0x28



Thanks!

Re: BUG: unable to handle kernel NULL pointer dereference

[matthieu Barthélemy]

=46inally I successfully remounted my partition. Here is how I've done
to recover, in case it can help someone else :
 I had to clone btrfs-progs-unstable tree.
Then checkout branch "tmp" (because I use compression, default
btrfs-progs are "too old"
Then I compiled btrfs-zero-log with "make btrfs-zero-log"
And finally ran "./btrfs-zero-log /dev/sda2"

Now I'm copying everything to a new partition, because I don't know if
can safely use the damaged one.

But wouldn't it be possible to avoid the "Null pointer" kernel crash
by checking what we do inside replay_one_buffer, and then
automatically clear log, or provide a "clear_log" mount option?
Any idea about what could have caused my problem?

Thanks.




2011/5/25 matthieu Barth=E9lemy <bonsouere@gmail.com>:
> Hi all,
>
> I have a Btrfs partition that cannot be mounted anymore, it makes
> kernel to crash.
> The partition was created a few months ago, with kernel 2.6.33 (with
> no special options) if I remember well. Since then, with new kernel
> releases, I enabled a few options : first space_cache, then compress,
> and finally with 2.6.38 compress=3Dlzo
> So the filesystem has now space_cache, data compressed with zlib AND =
lzo.
>
> With kernel 2.6.39-rc5 I had, a few weeks ago, a first crash where it
> complained about no free space. Then I rebooted on kernel 2.6.38,
> mounted the filesystem with the clear_cache option, and everything
> went fine, even returning back on kernel 2.6.39-rc5.
>
> But last week, while I was working (nothing special such as intensive
> read or writes), the system crashed because of Btrfs.
> Since then, I cannot mount my FS anymore.
> Here are the dmesg logs I gathered, testing with 2.6.39-rc5, and just
> to see if it made any difference, with the integration-test tree.
>
> Any idea about what happened? How can I help you to diagnose that? An=
y
> chance I could recover my data?
>
> Thanks.
>
> with 2.6.39-rc5 :
> # mount -o clear_cache,compress=3Dlzo /dev/sda2 /mnt/
>
> [ =A0676.767161] Btrfs loaded
> [ =A0676.774399] device fsid f24027efc24d32f7-2191b1da9df7d184 devid =
1
> transid 164511 /dev/sda2
> [ =A0676.775233] btrfs: force clearing of disk cache
> [ =A0676.775255] btrfs: use lzo compression
> [ =A0676.834811] btrfs: disk space caching is enabled
> [ =A0677.601773] BUG: unable to handle kernel NULL pointer dereferenc=
e at =A0 (null)
> [ =A0677.601800] IP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0
> [ =A0677.601822] *pde =3D 00000000
> [ =A0677.601834] Oops: 0000 [#1] SMP
> [ =A0677.601846] last sysfs file: /sys/devices/virtual/bdi/btrfs-1/ue=
vent
> [ =A0677.601861] Modules linked in: btrfs zlib_deflate af_packet
> snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel btusb
> snd_hda_codec bluetooth usb_storage snd_hwdep uas iTCO_wdt
> iTCO_vendor_support snd_pcm rfkill r8187se(C) uvcvideo videodev
> snd_timer media joydev wmi battery ac sg eeprom_93cx6 snd pcspkr
> soundcore r8169 snd_page_alloc ext4 jbd2 crc16 usbhid hid sd_mod
> ata_generic i915 ata_piix drm_kms_helper libata drm uhci_hcd scsi_mod
> ehci_hcd i2c_algo_bit rtc_cmos rtc_core rtc_lib usbcore intel_agp
> button video intel_gtt fan thermal processor thermal_sys hwmon
> [ =A0677.602034]
> [ =A0677.602046] Pid: 2401, comm: mount Tainted: G =A0 =A0 =A0 =A0 C
> 2.6.39-rc5-0.3-default #6 LG Electronics X110-L.A741B/X110
> [ =A0677.602068] EIP: 0060:[<c022bbfb>] EFLAGS: 00210202 CPU: 1
> [ =A0677.602082] EIP is at kmap_atomic_prot+0x1b/0xf0
> [ =A0677.602094] EAX: 00000000 EBX: 000004ca ECX: d9fee000 EDX: 00000=
163
> [ =A0677.602107] ESI: 00000000 EDI: 000004ca EBP: d9fefb88 ESP: d9fef=
b78
> [ =A0677.602121] =A0DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ =A0677.602134] Process mount (pid: 2401, ti=3Dd9fee000 task=3De61bf=
030
> task.ti=3Dd9fee000)
> [ =A0677.602147] Stack:
> [ =A0677.602156] =A0f64037c0 000004ca 00000000 000004ca d9fefb90 c022=
bcde
> d9fefbbc f853bab8
> [ =A0677.602179] =A000000000 c71c40f0 c68560a8 00000007 b7c09000 0000=
000e
> 00006572 c6850000
> [ =A0677.602202] =A000000f58 d9fefc24 f854b727 00006572 00000000 0000=
0000
> 00000000 00094689
> [ =A0677.602225] Call Trace:
> [ =A0677.602239] =A0[<c022bcde>] __kmap_atomic+0xe/0x10
> [ =A0677.602281] =A0[<f853bab8>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0677.602322] =A0[<f854b727>] add_inode_ref+0x1e7/0x330 [btrfs]
> [ =A0677.602363] =A0[<f854ccde>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0677.602404] =A0[<f854a431>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0677.602445] =A0[<f854a636>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0677.602463] =A0[<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
> [ =A0677.602503] =A0[<f854e8fe>] btrfs_recover_log_trees+0x1de/0x2b0 =
[btrfs]
> [ =A0677.602544] =A0[<f854cac0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0677.602596] =A0[<f8513a8c>] open_ctree+0x10bc/0x1410 [btrfs]
> [ =A0677.602615] =A0[<c03e9ca9>] ? strlcpy+0x39/0x60
> [ =A0677.602646] =A0[<f84f45e1>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0677.602664] =A0[<c02e3400>] ? pcpu_alloc+0x310/0x850
> [ =A0677.602681] =A0[<c03098d5>] mount_fs+0x35/0x180
> [ =A0677.602698] =A0[<c031e9d6>] vfs_kern_mount+0x46/0xa0
> [ =A0677.602712] =A0[<c031f7c9>] do_kern_mount+0x39/0xd0
> [ =A0677.602726] =A0[<c0320f34>] do_mount+0x594/0x6c0
> [ =A0677.602741] =A0[<c02d13d6>] ? __get_free_pages+0x26/0x30
> [ =A0677.602755] =A0[<c0320879>] ? copy_mount_options+0x39/0x120
> [ =A0677.602770] =A0[<c0321386>] sys_mount+0x66/0xa0
> [ =A0677.602786] =A0[<c05d021c>] sysenter_do_call+0x12/0x28
> [ =A0677.602798] Code: 8b 15 cc 42 82 c0 55 89 e5 e8 52 f9 ff ff 5d c=
3
> 55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
> 83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 db 78 c0 2b b=
1
> cc de
> [ =A0677.602902] EIP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0 SS:ESP =
0068:d9fefb78
> [ =A0677.602920] CR2: 0000000000000000
> [ =A0677.604805] [drm] Changing LVDS panel from (+hsync, +vsync) to
> (-hsync, -vsync)
> [ =A0677.854425] ---[ end trace b216833b014671c4 ]---
> [ =A0677.854452] note: mount[2401] exited with preempt_count 1
> [ =A0677.854731] BUG: scheduling while atomic: mount/2401/0x10000001
> [ =A0677.854753] Modules linked in: btrfs zlib_deflate af_packet
> snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel btusb
> snd_hda_codec bluetooth usb_storage snd_hwdep uas iTCO_wdt
> iTCO_vendor_support snd_pcm rfkill r8187se(C) uvcvideo videodev
> snd_timer media joydev wmi battery ac sg eeprom_93cx6 snd pcspkr
> soundcore r8169 snd_page_alloc ext4 jbd2 crc16 usbhid hid sd_mod
> ata_generic i915 ata_piix drm_kms_helper libata drm uhci_hcd scsi_mod
> ehci_hcd i2c_algo_bit rtc_cmos rtc_core rtc_lib usbcore intel_agp
> button video intel_gtt fan thermal processor thermal_sys hwmon
> [ =A0677.854935] Pid: 2401, comm: mount Tainted: G =A0 =A0 =A0D =A0C
> 2.6.39-rc5-0.3-default #6
> [ =A0677.854942] Call Trace:
> [ =A0677.854959] =A0[<c023420d>] __schedule_bug+0x5d/0x70
> [ =A0677.854971] =A0[<c05c7984>] schedule+0xa24/0xa30
> [ =A0677.854982] =A0[<c02d4310>] ? release_pages+0x1b0/0x1e0
> [ =A0677.854993] =A0[<c030838f>] ? fput+0x12f/0x1e0
> [ =A0677.855004] =A0[<c02ea9ca>] ? remove_vma+0x3a/0x50
> [ =A0677.855015] =A0[<c023f846>] __cond_resched+0x16/0x30
> [ =A0677.855024] =A0[<c05c7ba3>] _cond_resched+0x23/0x30
> [ =A0677.855034] =A0[<c0248cdc>] put_files_struct+0x6c/0xb0
> [ =A0677.855043] =A0[<c0248dac>] exit_files+0x3c/0x50
> [ =A0677.855051] =A0[<c02491de>] do_exit+0x15e/0x780
> [ =A0677.855060] =A0[<c0247227>] ? kmsg_dump+0x37/0xd0
> [ =A0677.855070] =A0[<c05c6c6d>] ? printk+0x28/0x2b
> [ =A0677.855080] =A0[<c05cad9d>] oops_end+0x8d/0xd0
> [ =A0677.855090] =A0[<c022700e>] no_context+0xbe/0x150
> [ =A0677.855100] =A0[<c0227227>] __bad_area_nosemaphore+0x37/0x170
> [ =A0677.855111] =A0[<c0227372>] bad_area_nosemaphore+0x12/0x20
> [ =A0677.855121] =A0[<c05ccc94>] do_page_fault+0x2c4/0x420
> [ =A0677.855131] =A0[<c02d0dbe>] ? __alloc_pages_nodemask+0xee/0x6e0
> [ =A0677.855142] =A0[<c022bc27>] ? kmap_atomic_prot+0x47/0xf0
> [ =A0677.855152] =A0[<c05cc9d0>] ? spurious_fault+0xd0/0xd0
> [ =A0677.855161] =A0[<c05ca34a>] error_code+0x5a/0x60
> [ =A0677.855171] =A0[<c05cc9d0>] ? spurious_fault+0xd0/0xd0
> [ =A0677.855180] =A0[<c022bbfb>] ? kmap_atomic_prot+0x1b/0xf0
> [ =A0677.855189] =A0[<c022bcde>] __kmap_atomic+0xe/0x10
> [ =A0677.855235] =A0[<f853bab8>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0677.855273] =A0[<f854b727>] add_inode_ref+0x1e7/0x330 [btrfs]
> [ =A0677.855318] =A0[<f854ccde>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0677.855358] =A0[<f854a431>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0677.855399] =A0[<f854a636>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0677.855410] =A0[<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
> [ =A0677.855446] =A0[<f854e8fe>] btrfs_recover_log_trees+0x1de/0x2b0 =
[btrfs]
> [ =A0677.855488] =A0[<f854cac0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0677.855539] =A0[<f8513a8c>] open_ctree+0x10bc/0x1410 [btrfs]
> [ =A0677.855552] =A0[<c03e9ca9>] ? strlcpy+0x39/0x60
> [ =A0677.855583] =A0[<f84f45e1>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0677.855594] =A0[<c02e3400>] ? pcpu_alloc+0x310/0x850
> [ =A0677.855604] =A0[<c03098d5>] mount_fs+0x35/0x180
> [ =A0677.855616] =A0[<c031e9d6>] vfs_kern_mount+0x46/0xa0
> [ =A0677.855625] =A0[<c031f7c9>] do_kern_mount+0x39/0xd0
> [ =A0677.855634] =A0[<c0320f34>] do_mount+0x594/0x6c0
> [ =A0677.855643] =A0[<c02d13d6>] ? __get_free_pages+0x26/0x30
> [ =A0677.855652] =A0[<c0320879>] ? copy_mount_options+0x39/0x120
> [ =A0677.855661] =A0[<c0321386>] sys_mount+0x66/0xa0
> [ =A0677.855672] =A0[<c05d021c>] sysenter_do_call+0x12/0x28
>
>
>
>
> with 2.6.39-rc5, without clear_cache option
> =A0# mount -o compress=3Dlzo /dev/sda2 /mnt/
> [ =A0138.393711] Btrfs loaded
> [ =A0138.415758] device fsid f24027efc24d32f7-2191b1da9df7d184 devid =
1
> transid 164511 /dev/sda2
> [ =A0138.416404] btrfs: use lzo compression
> [ =A0138.476160] btrfs: disk space caching is enabled
> [ =A0139.154606] block group 29360128 has an wrong amount of free spa=
ce
> [ =A0139.287457] BUG: unable to handle kernel NULL pointer dereferenc=
e at =A0 (null)
> [ =A0139.287484] IP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0
> [ =A0139.287506] *pde =3D 00000000
> [ =A0139.287518] Oops: 0000 [#1] SMP
> [ =A0139.287530] last sysfs file: /sys/devices/virtual/bdi/btrfs-1/ue=
vent
> [ =A0139.287544] Modules linked in: btrfs zlib_deflate af_packet
> snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
> snd_hda_codec snd_hwdep snd_pcm usb_storage uas snd_timer uvcvideo
> videodev iTCO_wdt iTCO_vendor_support snd soundcore snd_page_alloc
> media btusb pcspkr bluetooth r8187se(C) rfkill joydev battery r8169
> eeprom_93cx6 wmi sg ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
> i915 drm_kms_helper ata_piix drm uhci_hcd rtc_cmos rtc_core libata
> ehci_hcd i2c_algo_bit rtc_lib usbcore scsi_mod button intel_agp
> intel_gtt video fan thermal processor thermal_sys hwmon
> [ =A0139.287717]
> [ =A0139.287729] Pid: 2193, comm: mount Tainted: G =A0 =A0 =A0 =A0 C
> 2.6.39-rc5-0.3-default #6 LG Electronics X110-L.A741B/X110
> [ =A0139.287751] EIP: 0060:[<c022bbfb>] EFLAGS: 00210202 CPU: 1
> [ =A0139.287764] EIP is at kmap_atomic_prot+0x1b/0xf0
> [ =A0139.287777] EAX: 00000000 EBX: 000004ca ECX: cccc2000 EDX: 00000=
163
> [ =A0139.287790] ESI: 00000000 EDI: 000004ca EBP: cccc3b88 ESP: cccc3=
b78
> [ =A0139.287804] =A0DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ =A0139.287817] Process mount (pid: 2193, ti=3Dcccc2000 task=3Dccc90=
d30
> task.ti=3Dcccc2000)
> [ =A0139.287830] Stack:
> [ =A0139.287838] =A0f64037c0 000004ca 00000000 000004ca cccc3b90 c022=
bcde
> cccc3bbc f8935ab8
> [ =A0139.287861] =A000000000 d0570180 c92ce0a8 00000007 b7c09000 0000=
000e
> 00006572 c92c8000
> [ =A0139.287884] =A000000f58 cccc3c24 f8945727 00006572 00000000 0000=
0000
> 00000000 00094689
> [ =A0139.287907] Call Trace:
> [ =A0139.287921] =A0[<c022bcde>] __kmap_atomic+0xe/0x10
> [ =A0139.287963] =A0[<f8935ab8>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0139.288005] =A0[<f8945727>] add_inode_ref+0x1e7/0x330 [btrfs]
> [ =A0139.288056] =A0[<f8946cde>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0139.288098] =A0[<f8944431>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0139.288139] =A0[<f8944636>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0139.288157] =A0[<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
> [ =A0139.288197] =A0[<f89488fe>] btrfs_recover_log_trees+0x1de/0x2b0 =
[btrfs]
> [ =A0139.288238] =A0[<f8946ac0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0139.288290] =A0[<f890da8c>] open_ctree+0x10bc/0x1410 [btrfs]
> [ =A0139.288310] =A0[<c03e9ca9>] ? strlcpy+0x39/0x60
> [ =A0139.288341] =A0[<f88ee5e1>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0139.288359] =A0[<c02e3400>] ? pcpu_alloc+0x310/0x850
> [ =A0139.288375] =A0[<c03098d5>] mount_fs+0x35/0x180
> [ =A0139.288392] =A0[<c031e9d6>] vfs_kern_mount+0x46/0xa0
> [ =A0139.288407] =A0[<c031f7c9>] do_kern_mount+0x39/0xd0
> [ =A0139.288421] =A0[<c0320f34>] do_mount+0x594/0x6c0
> [ =A0139.288436] =A0[<c02d13d6>] ? __get_free_pages+0x26/0x30
> [ =A0139.288450] =A0[<c0320879>] ? copy_mount_options+0x39/0x120
> [ =A0139.288464] =A0[<c0321386>] sys_mount+0x66/0xa0
> [ =A0139.288481] =A0[<c05d021c>] sysenter_do_call+0x12/0x28
> [ =A0139.288493] Code: 8b 15 cc 42 82 c0 55 89 e5 e8 52 f9 ff ff 5d c=
3
> 55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
> 83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 db 78 c0 2b b=
1
> cc de
> [ =A0139.288595] EIP: [<c022bbfb>] kmap_atomic_prot+0x1b/0xf0 SS:ESP =
0068:cccc3b78
> [ =A0139.288614] CR2: 0000000000000000
> [ =A0139.310232] ---[ end trace 34b5224bc0e9db2d ]---
> [ =A0139.310259] note: mount[2193] exited with preempt_count 1
> [ =A0139.310531] BUG: scheduling while atomic: mount/2193/0x10000001
> [ =A0139.310553] Modules linked in: btrfs zlib_deflate af_packet
> snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device bnep edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
> snd_hda_codec snd_hwdep snd_pcm usb_storage uas snd_timer uvcvideo
> videodev iTCO_wdt iTCO_vendor_support snd soundcore snd_page_alloc
> media btusb pcspkr bluetooth r8187se(C) rfkill joydev battery r8169
> eeprom_93cx6 wmi sg ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generic
> i915 drm_kms_helper ata_piix drm uhci_hcd rtc_cmos rtc_core libata
> ehci_hcd i2c_algo_bit rtc_lib usbcore scsi_mod button intel_agp
> intel_gtt video fan thermal processor thermal_sys hwmon
> [ =A0139.310856] Pid: 2193, comm: mount Tainted: G =A0 =A0 =A0D =A0C
> 2.6.39-rc5-0.3-default #6
> [ =A0139.310881] Call Trace:
> [ =A0139.310911] =A0[<c023420d>] __schedule_bug+0x5d/0x70
> [ =A0139.310940] =A0[<c05c7984>] schedule+0xa24/0xa30
> [ =A0139.310967] =A0[<c02d4310>] ? release_pages+0x1b0/0x1e0
> [ =A0139.310995] =A0[<c030838f>] ? fput+0x12f/0x1e0
> [ =A0139.311022] =A0[<c02ea9ca>] ? remove_vma+0x3a/0x50
> [ =A0139.311048] =A0[<c023f846>] __cond_resched+0x16/0x30
> [ =A0139.311075] =A0[<c05c7ba3>] _cond_resched+0x23/0x30
> [ =A0139.311100] =A0[<c0248cdc>] put_files_struct+0x6c/0xb0
> [ =A0139.311126] =A0[<c0248dac>] exit_files+0x3c/0x50
> [ =A0139.311147] =A0[<c02491de>] do_exit+0x15e/0x780
> [ =A0139.311168] =A0[<c0247227>] ? kmsg_dump+0x37/0xd0
> [ =A0139.311189] =A0[<c05c6c6d>] ? printk+0x28/0x2b
> [ =A0139.311211] =A0[<c05cad9d>] oops_end+0x8d/0xd0
> [ =A0139.311233] =A0[<c022700e>] no_context+0xbe/0x150
> [ =A0139.311255] =A0[<c0227227>] __bad_area_nosemaphore+0x37/0x170
> [ =A0139.311279] =A0[<c0227372>] bad_area_nosemaphore+0x12/0x20
> [ =A0139.311301] =A0[<c05ccc94>] do_page_fault+0x2c4/0x420
> [ =A0139.311323] =A0[<c02d0dbe>] ? __alloc_pages_nodemask+0xee/0x6e0
> [ =A0139.311347] =A0[<c022bc27>] ? kmap_atomic_prot+0x47/0xf0
> [ =A0139.311373] =A0[<c05cc9d0>] ? spurious_fault+0xd0/0xd0
> [ =A0139.311398] =A0[<c05ca34a>] error_code+0x5a/0x60
> [ =A0139.311423] =A0[<c05cc9d0>] ? spurious_fault+0xd0/0xd0
> [ =A0139.311450] =A0[<c022bbfb>] ? kmap_atomic_prot+0x1b/0xf0
> [ =A0139.311476] =A0[<c022bcde>] __kmap_atomic+0xe/0x10
> [ =A0139.311537] =A0[<f8935ab8>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0139.311598] =A0[<f8945727>] add_inode_ref+0x1e7/0x330 [btrfs]
> [ =A0139.311657] =A0[<f8946cde>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0139.311710] =A0[<f8944431>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0139.311761] =A0[<f8944636>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0139.311786] =A0[<c03e7a2a>] ? radix_tree_lookup+0xa/0x10
> [ =A0139.311846] =A0[<f89488fe>] btrfs_recover_log_trees+0x1de/0x2b0 =
[btrfs]
> [ =A0139.311907] =A0[<f8946ac0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0139.311980] =A0[<f890da8c>] open_ctree+0x10bc/0x1410 [btrfs]
> [ =A0139.312038] =A0[<c03e9ca9>] ? strlcpy+0x39/0x60
> [ =A0139.312087] =A0[<f88ee5e1>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0139.312115] =A0[<c02e3400>] ? pcpu_alloc+0x310/0x850
> [ =A0139.312142] =A0[<c03098d5>] mount_fs+0x35/0x180
> [ =A0139.312171] =A0[<c031e9d6>] vfs_kern_mount+0x46/0xa0
> [ =A0139.312198] =A0[<c031f7c9>] do_kern_mount+0x39/0xd0
> [ =A0139.312223] =A0[<c0320f34>] do_mount+0x594/0x6c0
> [ =A0139.312249] =A0[<c02d13d6>] ? __get_free_pages+0x26/0x30
> [ =A0139.312275] =A0[<c0320879>] ? copy_mount_options+0x39/0x120
> [ =A0139.312302] =A0[<c0321386>] sys_mount+0x66/0xa0
> [ =A0139.312328] =A0[<c05d021c>] sysenter_do_call+0x12/0x28
>
>
>
> with integration-test tree (2011/05/24)
> # mount -o clear_cache,compress=3Dlzo /dev/sda2 /mnt/
> [ =A0295.895116] Btrfs loaded
> [ =A0295.906626] device fsid f24027efc24d32f7-2191b1da9df7d184 devid =
1
> transid 164511 /dev/sda2
> [ =A0295.907432] btrfs: force clearing of disk cache
> [ =A0295.907455] btrfs: use lzo compression
> [ =A0295.967015] btrfs: disk space caching is enabled
> [ =A0296.767248] BUG: unable to handle kernel NULL pointer dereferenc=
e at =A0 (null)
> [ =A0296.767274] IP: [<c022bcab>] kmap_atomic_prot+0x1b/0xf0
> [ =A0296.767298] *pde =3D 00000000
> [ =A0296.767310] Oops: 0000 [#1] SMP
> [ =A0296.767322] last sysfs file:
> /sys/devices/LNXSYSTM:00/device:00/PNP0A08:00/device:11/PNP0C09:00/PN=
P0C0A:00/power_supply/BAT1/voltage_now
> [ =A0296.767346] Modules linked in: btrfs zlib_deflate fuse af_packet
> snd_pcm_oss snd_mixer_oss snd_seq bnep snd_seq_device edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
> snd_hda_codec snd_hwdep snd_pcm snd_timer snd uvcvideo r8187se(C)
> btusb videodev soundcore usb_storage iTCO_wdt sg iTCO_vendor_support
> uas eeprom_93cx6 bluetooth r8169 wmi media rfkill snd_page_alloc
> joydev pcspkr battery ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generi=
c
> i915 drm_kms_helper uhci_hcd ata_piix drm ehci_hcd libata scsi_mod
> rtc_cmos intel_agp i2c_algo_bit usbcore intel_gtt rtc_core rtc_lib
> video button fan thermal processor thermal_sys hwmon
> [ =A0296.767523]
> [ =A0296.767534] Pid: 2299, comm: mount Tainted: G =A0 =A0 =A0 =A0 C
> 2.6.39-0.3-default+ #1 LG Electronics X110-L.A741B/X110
> [ =A0296.767556] EIP: 0060:[<c022bcab>] EFLAGS: 00210202 CPU: 1
> [ =A0296.767570] EIP is at kmap_atomic_prot+0x1b/0xf0
> [ =A0296.767582] EAX: 00000000 EBX: 000004ca ECX: d6c4e000 EDX: 00000=
163
> [ =A0296.767595] ESI: 00000000 EDI: 000004ca EBP: d6c4fb78 ESP: d6c4f=
b68
> [ =A0296.767609] =A0DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ =A0296.767623] Process mount (pid: 2299, ti=3Dd6c4e000 task=3Dd6c4c=
e70
> task.ti=3Dd6c4e000)
> [ =A0296.767636] Stack:
> [ =A0296.767644] =A0f4c037c0 000004ca 00000000 000004ca d6c4fb80 c022=
bd8e
> d6c4fbac f888a278
> [ =A0296.767667] =A000000000 e1ac3888 f400e0a8 00000007 b7c09000 0000=
000e
> 00006572 f4008000
> [ =A0296.767690] =A000000f58 d6c4fc20 f8899e5f 00006572 00000000 0000=
0000
> 00000000 00094689
> [ =A0296.767713] Call Trace:
> [ =A0296.767727] =A0[<c022bd8e>] __kmap_atomic+0xe/0x10
> [ =A0296.767770] =A0[<f888a278>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0296.767812] =A0[<f8899e5f>] add_inode_ref+0x22f/0x370 [btrfs]
> [ =A0296.767854] =A0[<f889b7fe>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0296.767897] =A0[<f8898e61>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0296.767939] =A0[<f8899066>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0296.767957] =A0[<c03e585a>] ? radix_tree_lookup+0xa/0x10
> [ =A0296.767998] =A0[<f889d47c>] btrfs_recover_log_trees+0x1dc/0x2a0 =
[btrfs]
> [ =A0296.768050] =A0[<f889b5e0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0296.768104] =A0[<f88624c5>] open_ctree+0x11c5/0x1510 [btrfs]
> [ =A0296.768124] =A0[<c03e7ad9>] ? strlcpy+0x39/0x60
> [ =A0296.768155] =A0[<f8842651>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0296.768174] =A0[<c02e2300>] ? pcpu_alloc+0x2c0/0x850
> [ =A0296.768192] =A0[<c0307f25>] mount_fs+0x35/0x180
> [ =A0296.768208] =A0[<c031cfe6>] vfs_kern_mount+0x46/0xa0
> [ =A0296.768223] =A0[<c031ddd9>] do_kern_mount+0x39/0xd0
> [ =A0296.768237] =A0[<c031f544>] do_mount+0x594/0x6c0
> [ =A0296.768253] =A0[<c02d02a6>] ? __get_free_pages+0x26/0x30
> [ =A0296.768268] =A0[<c031ee89>] ? copy_mount_options+0x39/0x120
> [ =A0296.768282] =A0[<c031f996>] sys_mount+0x66/0xa0
> [ =A0296.768298] =A0[<c05b745c>] sysenter_do_call+0x12/0x28
> [ =A0296.768310] Code: 8b 15 cc f2 7f c0 55 89 e5 e8 52 f9 ff ff 5d c=
3
> 55 89 e5 83 ec 10 89 e1 81 e1 00 e0 ff ff 89 5d f4 89 75 f8 89 7d fc
> 83 41 14 01 <8b> 08 c1 e9 1e 69 c9 80 03 00 00 8d b1 80 a8 76 c0 2b b=
1
> cc ab
> [ =A0296.768413] EIP: [<c022bcab>] kmap_atomic_prot+0x1b/0xf0 SS:ESP =
0068:d6c4fb68
> [ =A0296.768432] CR2: 0000000000000000
> [ =A0296.770367] [drm] Changing LVDS panel from (+hsync, +vsync) to
> (-hsync, -vsync)
> [ =A0296.949992] ---[ end trace 0963ef50bd4dfa03 ]---
> [ =A0296.950017] note: mount[2299] exited with preempt_count 1
> [ =A0296.950322] BUG: scheduling while atomic: mount/2299/0x10000001
> [ =A0296.950345] Modules linked in: btrfs zlib_deflate fuse af_packet
> snd_pcm_oss snd_mixer_oss snd_seq bnep snd_seq_device edd
> cpufreq_conservative microcode cpufreq_userspace cpufreq_powersave
> acpi_cpufreq mperf dm_mod snd_hda_codec_realtek snd_hda_intel
> snd_hda_codec snd_hwdep snd_pcm snd_timer snd uvcvideo r8187se(C)
> btusb videodev soundcore usb_storage iTCO_wdt sg iTCO_vendor_support
> uas eeprom_93cx6 bluetooth r8169 wmi media rfkill snd_page_alloc
> joydev pcspkr battery ac ext4 jbd2 crc16 usbhid hid sd_mod ata_generi=
c
> i915 drm_kms_helper uhci_hcd ata_piix drm ehci_hcd libata scsi_mod
> rtc_cmos intel_agp i2c_algo_bit usbcore intel_gtt rtc_core rtc_lib
> video button fan thermal processor thermal_sys hwmon
> [ =A0296.950537] Pid: 2299, comm: mount Tainted: G =A0 =A0 =A0D =A0C
> 2.6.39-0.3-default+ #1
> [ =A0296.950543] Call Trace:
> [ =A0296.950561] =A0[<c023438d>] __schedule_bug+0x5d/0x70
> [ =A0296.950573] =A0[<c05aea3d>] schedule+0x8cd/0xa60
> [ =A0296.950584] =A0[<c02d3280>] ? release_pages+0x1b0/0x1e0
> [ =A0296.950597] =A0[<c03069df>] ? fput+0x12f/0x1e0
> [ =A0296.950608] =A0[<c02e983a>] ? remove_vma+0x3a/0x50
> [ =A0296.950619] =A0[<c023f886>] __cond_resched+0x16/0x30
> [ =A0296.950628] =A0[<c05aede3>] _cond_resched+0x23/0x30
> [ =A0296.950637] =A0[<c0248cdc>] put_files_struct+0x6c/0xb0
> [ =A0296.950646] =A0[<c0248dac>] exit_files+0x3c/0x50
> [ =A0296.950655] =A0[<c02491de>] do_exit+0x15e/0x780
> [ =A0296.950664] =A0[<c0247227>] ? kmsg_dump+0x37/0xd0
> [ =A0296.950673] =A0[<c05ade7d>] ? printk+0x28/0x2b
> [ =A0296.950684] =A0[<c05b1fdd>] oops_end+0x8d/0xd0
> [ =A0296.950694] =A0[<c02270be>] no_context+0xbe/0x150
> [ =A0296.950704] =A0[<c02272d7>] __bad_area_nosemaphore+0x37/0x170
> [ =A0296.950714] =A0[<c0227422>] bad_area_nosemaphore+0x12/0x20
> [ =A0296.950724] =A0[<c05b3ed4>] do_page_fault+0x2c4/0x420
> [ =A0296.950735] =A0[<c02cfc8e>] ? __alloc_pages_nodemask+0xee/0x6e0
> [ =A0296.950746] =A0[<c022bcd7>] ? kmap_atomic_prot+0x47/0xf0
> [ =A0296.950757] =A0[<c05b3c10>] ? spurious_fault+0xd0/0xd0
> [ =A0296.950766] =A0[<c05b158a>] error_code+0x5a/0x60
> [ =A0296.950776] =A0[<c05b3c10>] ? spurious_fault+0xd0/0xd0
> [ =A0296.950785] =A0[<c022bcab>] ? kmap_atomic_prot+0x1b/0xf0
> [ =A0296.950794] =A0[<c022bd8e>] __kmap_atomic+0xe/0x10
> [ =A0296.950841] =A0[<f888a278>] read_extent_buffer+0x88/0x140 [btrfs=
]
> [ =A0296.950886] =A0[<f8899e5f>] add_inode_ref+0x22f/0x370 [btrfs]
> [ =A0296.950927] =A0[<f889b7fe>] replay_one_buffer+0x21e/0x2e0 [btrfs=
]
> [ =A0296.950972] =A0[<f8898e61>] walk_down_log_tree+0x1d1/0x360 [btrf=
s]
> [ =A0296.951012] =A0[<f8899066>] walk_log_tree+0x76/0x1e0 [btrfs]
> [ =A0296.951023] =A0[<c03e585a>] ? radix_tree_lookup+0xa/0x10
> [ =A0296.951064] =A0[<f889d47c>] btrfs_recover_log_trees+0x1dc/0x2a0 =
[btrfs]
> [ =A0296.951104] =A0[<f889b5e0>] ? replay_one_extent+0x6a0/0x6a0 [btr=
fs]
> [ =A0296.951156] =A0[<f88624c5>] open_ctree+0x11c5/0x1510 [btrfs]
> [ =A0296.951168] =A0[<c03e7ad9>] ? strlcpy+0x39/0x60
> [ =A0296.951198] =A0[<f8842651>] btrfs_mount+0x461/0x590 [btrfs]
> [ =A0296.951209] =A0[<c02e2300>] ? pcpu_alloc+0x2c0/0x850
> [ =A0296.951221] =A0[<c0307f25>] mount_fs+0x35/0x180
> [ =A0296.951232] =A0[<c031cfe6>] vfs_kern_mount+0x46/0xa0
> [ =A0296.951242] =A0[<c031ddd9>] do_kern_mount+0x39/0xd0
> [ =A0296.951251] =A0[<c031f544>] do_mount+0x594/0x6c0
> [ =A0296.951261] =A0[<c02d02a6>] ? __get_free_pages+0x26/0x30
> [ =A0296.951270] =A0[<c031ee89>] ? copy_mount_options+0x39/0x120
> [ =A0296.951279] =A0[<c031f996>] sys_mount+0x66/0xa0
> [ =A0296.951289] =A0[<c05b745c>] sysenter_do_call+0x12/0x28
>
>
>
> Thanks!
>
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Re: BUG: unable to handle kernel NULL pointer dereference

[Josef Bacik]

On 05/25/2011 01:41 PM, matthieu Barth=E9lemy wrote:
> Finally I successfully remounted my partition. Here is how I've done
> to recover, in case it can help someone else :
>  I had to clone btrfs-progs-unstable tree.
> Then checkout branch "tmp" (because I use compression, default
> btrfs-progs are "too old"
> Then I compiled btrfs-zero-log with "make btrfs-zero-log"
> And finally ran "./btrfs-zero-log /dev/sda2"
>=20
> Now I'm copying everything to a new partition, because I don't know i=
f
> can safely use the damaged one.
>=20
> But wouldn't it be possible to avoid the "Null pointer" kernel crash
> by checking what we do inside replay_one_buffer, and then
> automatically clear log, or provide a "clear_log" mount option?
> Any idea about what could have caused my problem?
>=20

Can you do a

gdb btrfs.ko

and then do

list *(add_inode_ref+0x1e7)

so I can see where it is.  It doesn't seem like either of those
read_extent_buffer's should screw up, either we do the proper checks or
it should have gone sideways before you got there.  Thanks,

Josef
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Re: BUG: unable to handle kernel NULL pointer dereference

[matthieu Barthélemy]

2011/5/25 Josef Bacik <josef@redhat.com>:
> On 05/25/2011 01:41 PM, matthieu Barth=E9lemy wrote:
>> Finally I successfully remounted my partition. Here is how I've done
>> to recover, in case it can help someone else :
>> =A0I had to clone btrfs-progs-unstable tree.
>> Then checkout branch "tmp" (because I use compression, default
>> btrfs-progs are "too old"
>> Then I compiled btrfs-zero-log with "make btrfs-zero-log"
>> And finally ran "./btrfs-zero-log /dev/sda2"
>>
>> Now I'm copying everything to a new partition, because I don't know =
if
>> can safely use the damaged one.
>>
>> But wouldn't it be possible to avoid the "Null pointer" kernel crash
>> by checking what we do inside replay_one_buffer, and then
>> automatically clear log, or provide a "clear_log" mount option?
>> Any idea about what could have caused my problem?
>>
>
> Can you do a
>
> gdb btrfs.ko
>
> and then do
>
> list *(add_inode_ref+0x1e7)

Sure, here it is :

 # gdb fs/btrfs/btrfs.ko
GNU gdb (GDB) SUSE (7.2-3.3)
[...]
Reading symbols from /home/btrfs-unstable/fs/btrfs/btrfs.ko...done.
(gdb) list *(add_inode_ref+0x1e7)
0x5ce47 is in add_inode_ref (fs/btrfs/tree-log.c:879).
874                      * if they are in the log.  if so, we allow the=
m to stay
875                      * otherwise they must be unlinked as a conflic=
t
876                      */
877                     ptr =3D btrfs_item_ptr_offset(leaf, path->slots=
[0]);
878                     ptr_end =3D ptr + btrfs_item_size_nr(leaf,
path->slots[0]);
879                     while (ptr < ptr_end) {
880                             victim_ref =3D (struct btrfs_inode_ref =
*)ptr;
881                             victim_name_len =3D btrfs_inode_ref_nam=
e_len(leaf,
882
    victim_ref);
883                             victim_name =3D kmalloc(victim_name_len=
,
GFP_NOFS);



> so I can see where it is. =A0It doesn't seem like either of those
> read_extent_buffer's should screw up, either we do the proper checks =
or
> it should have gone sideways before you got there. =A0Thanks,

Let me know everything I can do to help, I keep my old Btrfs partition
untouched just in case.

I've read in another thread that a new btrfsck will be released "in a
couple of days", this is great news, even if it doesn't handle my
particular problem.
Thanks for your help, and for working so hard on btrfs :-)


>
> Josef
>
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