[PATCH 1/1] - Fix reiserfs WARNING in dquot_writeback_dquots

[PATCH 1/1] - Fix reiserfs WARNING in dquot_writeback_dquots

[Tim Savannah]

[-- Attachment #1: Type: text/plain, Size: 3041 bytes --]

Oops, sent last one without patch on accident. Attached this time.


This has been happening for me since 4.10

dquot_writeback_dquots expects a lock to be held on super_block->s_umount ,

and reiserfs_sync_fs, which calls dquot_writeback_dquots, does not
obtain such a lock.

Thus, the following warning is generated:

[Sun May 28 04:58:06 2017] ------------[ cut here ]------------
[Sun May 28 04:58:06 2017] WARNING: CPU: 0 PID: 31 at
fs/quota/dquot.c:620 dquot_writeback_dquots+0x248/0x250
[Sun May 28 04:58:06 2017] Modules linked in: bbswitch(O)
nls_iso8859_1 nls_cp437 iTCO_wdt iTCO_vendor_support acer_wmi
sparse_keymap coretemp efi_pstore hwmon intel_rapl
x86_pkg_temp_thermal intel_powerclamp pcspkr ath9k ath9k_common
ath9k_hw ath efivars mac80211 joydev psmouse i2c_i801 cfg80211
input_leds led_class nvidiafb vgastate fb_ddc atl1c i915
drm_kms_helper drm intel_gtt syscopyarea sysfillrect sysimgblt mei_me
fb_sys_fops i2c_algo_bit mei lpc_ich shpchp acpi_cpufreq thermal wmi
video tpm_tis tpm_tis_core button tpm sch_fq_codel evdev mac_hid
uvcvideo vboxnetflt(O) videobuf2_vmalloc videobuf2_memops
vboxnetadp(O) videobuf2_v4l2 videobuf2_core pci_stub videodev
vboxpci(O) media ath3k btusb btrtl btbcm btintel vboxdrv(O) bluetooth
rfkill loop usbip_host usbip_core sg ip_tables x_tables hid_generic
usbhid
[Sun May 28 04:58:06 2017]  hid sr_mod cdrom sd_mod serio_raw atkbd
libps2 ehci_pci xhci_pci ahci xhci_hcd ehci_hcd libahci libata
scsi_mod usbcore usb_common i8042 serio raid1 raid0 dm_mod md_mod
[Sun May 28 04:58:06 2017] CPU: 0 PID: 31 Comm: kworker/0:1 Tainted: G
          O    4.11.3-1-ck2-ck #1
[Sun May 28 04:58:06 2017] Hardware name: Acer Aspire V3-771/VA70_HC,
BIOS V2.16 01/14/2013
[Sun May 28 04:58:06 2017] Workqueue: events_long flush_old_commits
[Sun May 28 04:58:06 2017] Call Trace:
[Sun May 28 04:58:06 2017]  ? dump_stack+0x5c/0x7a
[Sun May 28 04:58:06 2017]  ? __warn+0xb4/0xd0
[Sun May 27 04:58:06 2017]  ? dquot_writeback_dquots+0x248/0x250
[Sun May 27 04:58:06 2017]  ? reiserfs_sync_fs+0x12/0x70
[Sun May 27 04:58:06 2017]  ? dbs_work_handler+0x3d/0x50
[Sun May 27 04:58:06 2017]  ? flush_old_commits+0x30/0x50
[Sun May 27 04:58:06 2017]  ? process_one_work+0x1b1/0x3a0
[Sun May 27 04:58:06 2017]  ? worker_thread+0x42/0x4c0
[Sun May 27 04:58:06 2017]  ? kthread+0xf2/0x130
[Sun May 27 04:58:06 2017]  ? process_one_work+0x3a0/0x3a0
[Sun May 27 04:58:06 2017]  ? kthread_create_on_node+0x40/0x40
[Sun May 27 04:58:06 2017]  ? ret_from_fork+0x26/0x40
[Sun May 27 04:58:06 2017] ---[ end trace 7e040d020ba99607 ]---


This occurs during system boot on a fully-updated Archlinux system,
and has so since 4.10 100% of the time. It may occur after as well,
but it's a WARN_ONCE.

The attached patch corrects this issue by first trying to obtain a
readlock on said structure member, and if it got it, releases it
before returning.

After applying the patch, my system is completely stable and the
warning no longer occurs. Mounting and unmounting works as expected
without issue.

Thanks,
- Tim Savannah

[-- Attachment #2: fix-reiserfs-dquot-warning.patch --]
[-- Type: text/x-patch, Size: 710 bytes --]

--- a/fs/reiserfs/super.c	2017-05-29 00:14:45.000000000 -0400
+++ b/fs/reiserfs/super.c	2017-05-29 00:51:44.000000000 -0400
@@ -67,17 +67,28 @@
 static int reiserfs_sync_fs(struct super_block *s, int wait)
 {
 	struct reiserfs_transaction_handle th;
+	int got_lock;
 
 	/*
 	 * Writeback quota in non-journalled quota case - journalled quota has
 	 * no dirty dquots
 	 */
+
+	if ( down_read_trylock(&s->s_umount) )
+		got_lock = 1;
+	else
+		got_lock = 0;
+
 	dquot_writeback_dquots(s, -1);
 	reiserfs_write_lock(s);
 	if (!journal_begin(&th, s, 1))
 		if (!journal_end_sync(&th))
 			reiserfs_flush_old_commits(s);
 	reiserfs_write_unlock(s);
+
+	if ( got_lock )
+		up_read(&s->s_umount);
+
 	return 0;
 }
 

Re: [PATCH 1/1] - Fix reiserfs WARNING in dquot_writeback_dquots

[Tim Savannah]

Any comments? Can we get this merged, or some variation? It affects a
lot more than just all my machines. Google shows this traceback is
occurring for others as well.

On Mon, May 29, 2017 at 12:57 AM, Tim Savannah <kata198@gmail.com> wrote:
> Oops, sent last one without patch on accident. Attached this time.
>
>
> This has been happening for me since 4.10
>
> dquot_writeback_dquots expects a lock to be held on super_block->s_umount ,
>
> and reiserfs_sync_fs, which calls dquot_writeback_dquots, does not
> obtain such a lock.
>
> Thus, the following warning is generated:
>
> [Sun May 28 04:58:06 2017] ------------[ cut here ]------------
> [Sun May 28 04:58:06 2017] WARNING: CPU: 0 PID: 31 at
> fs/quota/dquot.c:620 dquot_writeback_dquots+0x248/0x250
> [Sun May 28 04:58:06 2017] Modules linked in: bbswitch(O)
> nls_iso8859_1 nls_cp437 iTCO_wdt iTCO_vendor_support acer_wmi
> sparse_keymap coretemp efi_pstore hwmon intel_rapl
> x86_pkg_temp_thermal intel_powerclamp pcspkr ath9k ath9k_common
> ath9k_hw ath efivars mac80211 joydev psmouse i2c_i801 cfg80211
> input_leds led_class nvidiafb vgastate fb_ddc atl1c i915
> drm_kms_helper drm intel_gtt syscopyarea sysfillrect sysimgblt mei_me
> fb_sys_fops i2c_algo_bit mei lpc_ich shpchp acpi_cpufreq thermal wmi
> video tpm_tis tpm_tis_core button tpm sch_fq_codel evdev mac_hid
> uvcvideo vboxnetflt(O) videobuf2_vmalloc videobuf2_memops
> vboxnetadp(O) videobuf2_v4l2 videobuf2_core pci_stub videodev
> vboxpci(O) media ath3k btusb btrtl btbcm btintel vboxdrv(O) bluetooth
> rfkill loop usbip_host usbip_core sg ip_tables x_tables hid_generic
> usbhid
> [Sun May 28 04:58:06 2017]  hid sr_mod cdrom sd_mod serio_raw atkbd
> libps2 ehci_pci xhci_pci ahci xhci_hcd ehci_hcd libahci libata
> scsi_mod usbcore usb_common i8042 serio raid1 raid0 dm_mod md_mod
> [Sun May 28 04:58:06 2017] CPU: 0 PID: 31 Comm: kworker/0:1 Tainted: G
>           O    4.11.3-1-ck2-ck #1
> [Sun May 28 04:58:06 2017] Hardware name: Acer Aspire V3-771/VA70_HC,
> BIOS V2.16 01/14/2013
> [Sun May 28 04:58:06 2017] Workqueue: events_long flush_old_commits
> [Sun May 28 04:58:06 2017] Call Trace:
> [Sun May 28 04:58:06 2017]  ? dump_stack+0x5c/0x7a
> [Sun May 28 04:58:06 2017]  ? __warn+0xb4/0xd0
> [Sun May 27 04:58:06 2017]  ? dquot_writeback_dquots+0x248/0x250
> [Sun May 27 04:58:06 2017]  ? reiserfs_sync_fs+0x12/0x70
> [Sun May 27 04:58:06 2017]  ? dbs_work_handler+0x3d/0x50
> [Sun May 27 04:58:06 2017]  ? flush_old_commits+0x30/0x50
> [Sun May 27 04:58:06 2017]  ? process_one_work+0x1b1/0x3a0
> [Sun May 27 04:58:06 2017]  ? worker_thread+0x42/0x4c0
> [Sun May 27 04:58:06 2017]  ? kthread+0xf2/0x130
> [Sun May 27 04:58:06 2017]  ? process_one_work+0x3a0/0x3a0
> [Sun May 27 04:58:06 2017]  ? kthread_create_on_node+0x40/0x40
> [Sun May 27 04:58:06 2017]  ? ret_from_fork+0x26/0x40
> [Sun May 27 04:58:06 2017] ---[ end trace 7e040d020ba99607 ]---
>
>
> This occurs during system boot on a fully-updated Archlinux system,
> and has so since 4.10 100% of the time. It may occur after as well,
> but it's a WARN_ONCE.
>
> The attached patch corrects this issue by first trying to obtain a
> readlock on said structure member, and if it got it, releases it
> before returning.
>
> After applying the patch, my system is completely stable and the
> warning no longer occurs. Mounting and unmounting works as expected
> without issue.
>
> Thanks,
> - Tim Savannah

Re: [PATCH 1/1] - Fix reiserfs WARNING in dquot_writeback_dquots

[Jeff Mahoney]

[-- Attachment #1.1: Type: text/plain, Size: 6353 bytes --]

On 6/14/17 11:27 PM, Tim Savannah wrote:
> Any comments? Can we get this merged, or some variation? It affects a
> lot more than just all my machines. Google shows this traceback is
> occurring for others as well.

Hi Tim -

This patch was merged for 4.12:

commit 1e0e653f1136a413a9969e5d0d548ee6499b9763
Author: Jan Kara <jack@suse.cz>
Date:   Wed Apr 5 14:17:30 2017 +0200

    reiserfs: Protect dquot_writeback_dquots() by s_umount semaphore

    dquot_writeback_dquots() expects s_umount semaphore to be held to
    protect it from other concurrent quota operations. reiserfs_sync_fs()
    can call dquot_writeback_dquots() without holding s_umount semaphore
    when called from flush_old_commits().

    Fix the problem by grabbing s_umount in flush_old_commits(). However we
    have to be careful and use only trylock since reiserfs_cancel_old_sync()
    can be waiting for flush_old_commits() to complete while holding
    s_umount semaphore. Possible postponing of sync work is not a big deal
    though as that is only an opportunistic flush.

    Fixes: 9d1ccbe70e0b14545caad12dc73adb3605447df0
    Reported-by: Jan Beulich <jbeulich@suse.com>
    Signed-off-by: Jan Kara <jack@suse.cz>

Your patch was not correct.  I'll provide review below if you're interested in the details.

> On Mon, May 29, 2017 at 12:57 AM, Tim Savannah <kata198@gmail.com> wrote:
>> Oops, sent last one without patch on accident. Attached this time.
>>
>>
>> This has been happening for me since 4.10
>>
>> dquot_writeback_dquots expects a lock to be held on super_block->s_umount ,
>>
>> and reiserfs_sync_fs, which calls dquot_writeback_dquots, does not
>> obtain such a lock.
>>
>> Thus, the following warning is generated:
>>
>> [Sun May 28 04:58:06 2017] ------------[ cut here ]------------
>> [Sun May 28 04:58:06 2017] WARNING: CPU: 0 PID: 31 at
>> fs/quota/dquot.c:620 dquot_writeback_dquots+0x248/0x250
>> [Sun May 28 04:58:06 2017] Modules linked in: bbswitch(O)
>> nls_iso8859_1 nls_cp437 iTCO_wdt iTCO_vendor_support acer_wmi
>> sparse_keymap coretemp efi_pstore hwmon intel_rapl
>> x86_pkg_temp_thermal intel_powerclamp pcspkr ath9k ath9k_common
>> ath9k_hw ath efivars mac80211 joydev psmouse i2c_i801 cfg80211
>> input_leds led_class nvidiafb vgastate fb_ddc atl1c i915
>> drm_kms_helper drm intel_gtt syscopyarea sysfillrect sysimgblt mei_me
>> fb_sys_fops i2c_algo_bit mei lpc_ich shpchp acpi_cpufreq thermal wmi
>> video tpm_tis tpm_tis_core button tpm sch_fq_codel evdev mac_hid
>> uvcvideo vboxnetflt(O) videobuf2_vmalloc videobuf2_memops
>> vboxnetadp(O) videobuf2_v4l2 videobuf2_core pci_stub videodev
>> vboxpci(O) media ath3k btusb btrtl btbcm btintel vboxdrv(O) bluetooth
>> rfkill loop usbip_host usbip_core sg ip_tables x_tables hid_generic
>> usbhid
>> [Sun May 28 04:58:06 2017]  hid sr_mod cdrom sd_mod serio_raw atkbd
>> libps2 ehci_pci xhci_pci ahci xhci_hcd ehci_hcd libahci libata
>> scsi_mod usbcore usb_common i8042 serio raid1 raid0 dm_mod md_mod
>> [Sun May 28 04:58:06 2017] CPU: 0 PID: 31 Comm: kworker/0:1 Tainted: G
>>           O    4.11.3-1-ck2-ck #1
>> [Sun May 28 04:58:06 2017] Hardware name: Acer Aspire V3-771/VA70_HC,
>> BIOS V2.16 01/14/2013
>> [Sun May 28 04:58:06 2017] Workqueue: events_long flush_old_commits
>> [Sun May 28 04:58:06 2017] Call Trace:
>> [Sun May 28 04:58:06 2017]  ? dump_stack+0x5c/0x7a
>> [Sun May 28 04:58:06 2017]  ? __warn+0xb4/0xd0
>> [Sun May 27 04:58:06 2017]  ? dquot_writeback_dquots+0x248/0x250
>> [Sun May 27 04:58:06 2017]  ? reiserfs_sync_fs+0x12/0x70
>> [Sun May 27 04:58:06 2017]  ? dbs_work_handler+0x3d/0x50
>> [Sun May 27 04:58:06 2017]  ? flush_old_commits+0x30/0x50
>> [Sun May 27 04:58:06 2017]  ? process_one_work+0x1b1/0x3a0
>> [Sun May 27 04:58:06 2017]  ? worker_thread+0x42/0x4c0
>> [Sun May 27 04:58:06 2017]  ? kthread+0xf2/0x130
>> [Sun May 27 04:58:06 2017]  ? process_one_work+0x3a0/0x3a0
>> [Sun May 27 04:58:06 2017]  ? kthread_create_on_node+0x40/0x40
>> [Sun May 27 04:58:06 2017]  ? ret_from_fork+0x26/0x40
>> [Sun May 27 04:58:06 2017] ---[ end trace 7e040d020ba99607 ]---
>>
>>
>> This occurs during system boot on a fully-updated Archlinux system,
>> and has so since 4.10 100% of the time. It may occur after as well,
>> but it's a WARN_ONCE.
>>
>> The attached patch corrects this issue by first trying to obtain a
>> readlock on said structure member, and if it got it, releases it
>> before returning.

In the future, please include your patch inline as part of the message.

>> After applying the patch, my system is completely stable and the
>> warning no longer occurs. Mounting and unmounting works as expected
>> without issue.

I suspect this is because you aren't doing any of the things that would
conflict here.  Remounting, freeze/thaw, or really anything that takes
->s_umount as a writer running in a different thread would cause problems.

> --- a/fs/reiserfs/super.c	2017-05-29 00:14:45.000000000 -0400
> +++ b/fs/reiserfs/super.c	2017-05-29 00:51:44.000000000 -0400
> @@ -67,17 +67,28 @@
>  static int reiserfs_sync_fs(struct super_block *s, int wait)
>  {
>  	struct reiserfs_transaction_handle th;
> +	int got_lock;
>  
>  	/*
>  	 * Writeback quota in non-journalled quota case - journalled quota has
>  	 * no dirty dquots
>  	 */
> +
> +	if ( down_read_trylock(&s->s_umount) )
> +		got_lock = 1;
> +	else
> +		got_lock = 0;
> +
> 

This is pretty much the same as not using the lock.  The lock is a requirement to
continue and assuming that if we can't get the lock that we must already be holding
it is incorrect.  There may be other threads executing with s->s_umount held as writers
and this patch means that this would execute concurrently, which is incorrect.

>  	dquot_writeback_dquots(s, -1);
>  	reiserfs_write_lock(s);
>  	if (!journal_begin(&th, s, 1))
>  		if (!journal_end_sync(&th))
>  			reiserfs_flush_old_commits(s);
>  	reiserfs_write_unlock(s);
> +
> +	if ( got_lock )
> +		up_read(&s->s_umount);
> +
>  	return 0;
>  }

Please follow the surrounding style.  Spaces within the conditional are
not part of the accepted style[1].

-Jeff

[1] https://github.com/torvalds/linux/blob/master/Documentation/process/coding-style.rst

-- 
Jeff Mahoney
SUSE Labs


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

[PATCH 1/1] - Fix reiserfs WARNING in dquot_writeback_dquots

[Tim Savannah]

This has been happening for me since 4.10

dquot_writeback_dquots expects a lock to be held on super_block->s_umount ,

and reiserfs_sync_fs, which calls dquot_writeback_dquots, does not
obtain such a lock.

Thus, the following warning is generated:

[Sun May 28 04:58:06 2017] ------------[ cut here ]------------
[Sun May 28 04:58:06 2017] WARNING: CPU: 0 PID: 31 at
fs/quota/dquot.c:620 dquot_writeback_dquots+0x248/0x250
[Sun May 28 04:58:06 2017] Modules linked in: bbswitch(O)
nls_iso8859_1 nls_cp437 iTCO_wdt iTCO_vendor_support acer_wmi
sparse_keymap coretemp efi_pstore hwmon intel_rapl
x86_pkg_temp_thermal intel_powerclamp pcspkr ath9k ath9k_common
ath9k_hw ath efivars mac80211 joydev psmouse i2c_i801 cfg80211
input_leds led_class nvidiafb vgastate fb_ddc atl1c i915
drm_kms_helper drm intel_gtt syscopyarea sysfillrect sysimgblt mei_me
fb_sys_fops i2c_algo_bit mei lpc_ich shpchp acpi_cpufreq thermal wmi
video tpm_tis tpm_tis_core button tpm sch_fq_codel evdev mac_hid
uvcvideo vboxnetflt(O) videobuf2_vmalloc videobuf2_memops
vboxnetadp(O) videobuf2_v4l2 videobuf2_core pci_stub videodev
vboxpci(O) media ath3k btusb btrtl btbcm btintel vboxdrv(O) bluetooth
rfkill loop usbip_host usbip_core sg ip_tables x_tables hid_generic
usbhid
[Sun May 28 04:58:06 2017]  hid sr_mod cdrom sd_mod serio_raw atkbd
libps2 ehci_pci xhci_pci ahci xhci_hcd ehci_hcd libahci libata
scsi_mod usbcore usb_common i8042 serio raid1 raid0 dm_mod md_mod
[Sun May 28 04:58:06 2017] CPU: 0 PID: 31 Comm: kworker/0:1 Tainted: G
          O    4.11.3-1-ck2-ck #1
[Sun May 28 04:58:06 2017] Hardware name: Acer Aspire V3-771/VA70_HC,
BIOS V2.16 01/14/2013
[Sun May 28 04:58:06 2017] Workqueue: events_long flush_old_commits
[Sun May 28 04:58:06 2017] Call Trace:
[Sun May 28 04:58:06 2017]  ? dump_stack+0x5c/0x7a
[Sun May 28 04:58:06 2017]  ? __warn+0xb4/0xd0
[Sun May 27 04:58:06 2017]  ? dquot_writeback_dquots+0x248/0x250
[Sun May 27 04:58:06 2017]  ? reiserfs_sync_fs+0x12/0x70
[Sun May 27 04:58:06 2017]  ? dbs_work_handler+0x3d/0x50
[Sun May 27 04:58:06 2017]  ? flush_old_commits+0x30/0x50
[Sun May 27 04:58:06 2017]  ? process_one_work+0x1b1/0x3a0
[Sun May 27 04:58:06 2017]  ? worker_thread+0x42/0x4c0
[Sun May 27 04:58:06 2017]  ? kthread+0xf2/0x130
[Sun May 27 04:58:06 2017]  ? process_one_work+0x3a0/0x3a0
[Sun May 27 04:58:06 2017]  ? kthread_create_on_node+0x40/0x40
[Sun May 27 04:58:06 2017]  ? ret_from_fork+0x26/0x40
[Sun May 27 04:58:06 2017] ---[ end trace 7e040d020ba99607 ]---


This occurs during system boot on a fully-updated Archlinux system,
and has so since 4.10 100% of the time. It may occur after as well,
but it's a WARN_ONCE.

The attached patch corrects this issue by first trying to obtain a
readlock on said structure member, and if it got it, releases it
before returning.

After applying the patch, my system is completely stable and the
warning no longer occurs. Mounting and unmounting works as expected
without issue.

Thanks,
- Tim Savannah