btrfs check --repair is clean, but mount fails

btrfs check --repair is clean, but mount fails

[Marc MERLIN]

btrfs-tools 4.4-1
gargamel:~# uname -r
4.4.2-amd64-i915-volpreempt-20160214bc2

2 drive array stopped working after a crash/reboot. Check --repair finds nothing wrong with it:

gargamel:~# btrfs check --repair /dev/mapper/raid0d1
enabling repair mode
Checking filesystem on /dev/mapper/raid0d1
UUID: 01334b81-c0db-4e80-92e4-cac4da867651
checking extents
Fixed 0 roots.
checking free space cache
cache and super generation don't match, space cache will be invalidated
checking fs roots
checking csums
checking root refs
found 1201345524312 bytes used err is 0
total csum bytes: 1165124220
total tree bytes: 8258322432
total fs tree bytes: 5574197248
total extent tree bytes: 1020428288
btree space waste bytes: 1902023247
file data blocks allocated: 1193398628352
 referenced 1209324777472
gargamel:~# mount /var/local/space
mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so
[ 8200.511021] BTRFS info (device dm-6): disk space caching is enabled
[ 8200.533030] BTRFS: failed to read the system array on dm-6
[ 8200.582097] BTRFS: open_ctree failed


gargamel:~# btrfs check --repair /dev/mapper/raid0d2
enabling repair mode
Checking filesystem on /dev/mapper/raid0d2
UUID: 01334b81-c0db-4e80-92e4-cac4da867651
checking extents
Fixed 0 roots.
checking free space cache
cache and super generation don't match, space cache will be invalidated
checking fs roots
checking csums
checking root refs
found 1201345540696 bytes used err is 0
total csum bytes: 1165124220
total tree bytes: 8258338816
total fs tree bytes: 5574197248
total extent tree bytes: 1020444672
btree space waste bytes: 1902039421
file data blocks allocated: 1193398628352
 referenced 1209324777472
gargamel:~# mount /var/local/space
mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
[13373.606737] BTRFS info (device dm-6): disk space caching is enabled
[13373.628682] BTRFS: failed to read the system array on dm-6
[13373.672607] BTRFS: open_ctree failed

-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  

Re: btrfs check --repair is clean, but mount fails

[Liu Bo]

On Fri, Feb 26, 2016 at 06:39:38PM -0800, Marc MERLIN wrote:
> btrfs-tools 4.4-1
> gargamel:~# uname -r
> 4.4.2-amd64-i915-volpreempt-20160214bc2
> 
> 2 drive array stopped working after a crash/reboot. Check --repair finds nothing wrong with it:
> 
> gargamel:~# btrfs check --repair /dev/mapper/raid0d1
> enabling repair mode
> Checking filesystem on /dev/mapper/raid0d1
> UUID: 01334b81-c0db-4e80-92e4-cac4da867651
> checking extents
> Fixed 0 roots.
> checking free space cache
> cache and super generation don't match, space cache will be invalidated
> checking fs roots
> checking csums
> checking root refs
> found 1201345524312 bytes used err is 0
> total csum bytes: 1165124220
> total tree bytes: 8258322432
> total fs tree bytes: 5574197248
> total extent tree bytes: 1020428288
> btree space waste bytes: 1902023247
> file data blocks allocated: 1193398628352
>  referenced 1209324777472
> gargamel:~# mount /var/local/space
> mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> [ 8200.511021] BTRFS info (device dm-6): disk space caching is enabled
> [ 8200.533030] BTRFS: failed to read the system array on dm-6
> [ 8200.582097] BTRFS: open_ctree failed

Does 'btrfs dev scan' help?

Thanks,

-liubo

> 
> 
> gargamel:~# btrfs check --repair /dev/mapper/raid0d2
> enabling repair mode
> Checking filesystem on /dev/mapper/raid0d2
> UUID: 01334b81-c0db-4e80-92e4-cac4da867651
> checking extents
> Fixed 0 roots.
> checking free space cache
> cache and super generation don't match, space cache will be invalidated
> checking fs roots
> checking csums
> checking root refs
> found 1201345540696 bytes used err is 0
> total csum bytes: 1165124220
> total tree bytes: 8258338816
> total fs tree bytes: 5574197248
> total extent tree bytes: 1020444672
> btree space waste bytes: 1902039421
> file data blocks allocated: 1193398628352
>  referenced 1209324777472
> gargamel:~# mount /var/local/space
> mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
> [13373.606737] BTRFS info (device dm-6): disk space caching is enabled
> [13373.628682] BTRFS: failed to read the system array on dm-6
> [13373.672607] BTRFS: open_ctree failed
> 
> -- 
> "A mouse is a device used to point at the xterm you want to type in" - A.S.R.
> Microsoft is to operating systems ....
>                                       .... what McDonalds is to gourmet cooking
> Home page: http://marc.merlins.org/  
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Fri, Feb 26, 2016 at 06:45:34PM -0800, Liu Bo wrote:
> On Fri, Feb 26, 2016 at 06:39:38PM -0800, Marc MERLIN wrote:
> > btrfs-tools 4.4-1
> > gargamel:~# uname -r
> > 4.4.2-amd64-i915-volpreempt-20160214bc2
> > 
> > 2 drive array stopped working after a crash/reboot. Check --repair finds nothing wrong with it:
> > 
> > gargamel:~# btrfs check --repair /dev/mapper/raid0d1
> > enabling repair mode
> > Checking filesystem on /dev/mapper/raid0d1
> > UUID: 01334b81-c0db-4e80-92e4-cac4da867651
> > checking extents
> > Fixed 0 roots.
> > checking free space cache
> > cache and super generation don't match, space cache will be invalidated
> > checking fs roots
> > checking csums
> > checking root refs
> > found 1201345524312 bytes used err is 0
> > total csum bytes: 1165124220
> > total tree bytes: 8258322432
> > total fs tree bytes: 5574197248
> > total extent tree bytes: 1020428288
> > btree space waste bytes: 1902023247
> > file data blocks allocated: 1193398628352
> >  referenced 1209324777472
> > gargamel:~# mount /var/local/space
> > mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
> >        missing codepage or helper program, or other error
> >        In some cases useful info is found in syslog - try
> >        dmesg | tail  or so
> > [ 8200.511021] BTRFS info (device dm-6): disk space caching is enabled
> > [ 8200.533030] BTRFS: failed to read the system array on dm-6
> > [ 8200.582097] BTRFS: open_ctree failed
> 
> Does 'btrfs dev scan' help?
 
Oh my, it does...
gargamel:~# btrfs dev scan
Scanning for Btrfs filesystems
gargamel:~# mount /var/local/space

[14477.028083] BTRFS: device label btrfs_space devid 2 transid 776784 /dev/mapper/raid0d2
[14500.262307] BTRFS info (device dm-7): disk space caching is enabled
[14504.042485] BTRFS: checking UUID tree

Err, I'm very perplexed now. I already have a scan in my boot process after device decrypts. 
Somehow it saw one of my 2 devices, but not the other one?

I'm looking at my boot:
[  112.063677] BTRFS: device label btrfs_space devid 1 transid 776782 /dev/mapper/raid0d1
[  112.090192] BTRFS info (device dm-6): disk space caching is enabled
[  112.111740] BTRFS: failed to read the system array on dm-6
[  112.160047] BTRFS: open_ctree failed
[  112.269710] BTRFS info (device dm-6): disk space caching is enabled
[  112.291430] BTRFS: failed to read the system array on dm-6
[  112.320104] BTRFS: open_ctree failed

So dm-6 is: raid0d1 -> ../dm-6

So, raid0d1 had an issue, btrfs check didn't really report any, for some unknown 
reason this caused raid0d2 not to be scanned, and in turn this caused
mounting that filesystem to fail?

Or did btrfs check actually fix something that I missed?
Any why would scan have missed raid0d2 the first time around?

Is it complaining that it can't read btrfs structures from raid0d1 because raid0d2
wasn't known yet? I'm not too sure what open_ctree means in that context.

Thanks,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  

Re: btrfs check --repair is clean, but mount fails

[Liu Bo]

On Fri, Feb 26, 2016 at 07:03:04PM -0800, Marc MERLIN wrote:
> On Fri, Feb 26, 2016 at 06:45:34PM -0800, Liu Bo wrote:
> > On Fri, Feb 26, 2016 at 06:39:38PM -0800, Marc MERLIN wrote:
> > > btrfs-tools 4.4-1
> > > gargamel:~# uname -r
> > > 4.4.2-amd64-i915-volpreempt-20160214bc2
> > > 
> > > 2 drive array stopped working after a crash/reboot. Check --repair finds nothing wrong with it:
> > > 
> > > gargamel:~# btrfs check --repair /dev/mapper/raid0d1
> > > enabling repair mode
> > > Checking filesystem on /dev/mapper/raid0d1
> > > UUID: 01334b81-c0db-4e80-92e4-cac4da867651
> > > checking extents
> > > Fixed 0 roots.
> > > checking free space cache
> > > cache and super generation don't match, space cache will be invalidated
> > > checking fs roots
> > > checking csums
> > > checking root refs
> > > found 1201345524312 bytes used err is 0
> > > total csum bytes: 1165124220
> > > total tree bytes: 8258322432
> > > total fs tree bytes: 5574197248
> > > total extent tree bytes: 1020428288
> > > btree space waste bytes: 1902023247
> > > file data blocks allocated: 1193398628352
> > >  referenced 1209324777472
> > > gargamel:~# mount /var/local/space
> > > mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
> > >        missing codepage or helper program, or other error
> > >        In some cases useful info is found in syslog - try
> > >        dmesg | tail  or so
> > > [ 8200.511021] BTRFS info (device dm-6): disk space caching is enabled
> > > [ 8200.533030] BTRFS: failed to read the system array on dm-6
> > > [ 8200.582097] BTRFS: open_ctree failed
> > 
> > Does 'btrfs dev scan' help?
>  
> Oh my, it does...
> gargamel:~# btrfs dev scan
> Scanning for Btrfs filesystems
> gargamel:~# mount /var/local/space
> 
> [14477.028083] BTRFS: device label btrfs_space devid 2 transid 776784 /dev/mapper/raid0d2
> [14500.262307] BTRFS info (device dm-7): disk space caching is enabled
> [14504.042485] BTRFS: checking UUID tree
> 
> Err, I'm very perplexed now. I already have a scan in my boot process after device decrypts. 
> Somehow it saw one of my 2 devices, but not the other one?
> 
> I'm looking at my boot:
> [  112.063677] BTRFS: device label btrfs_space devid 1 transid 776782 /dev/mapper/raid0d1
> [  112.090192] BTRFS info (device dm-6): disk space caching is enabled
> [  112.111740] BTRFS: failed to read the system array on dm-6
> [  112.160047] BTRFS: open_ctree failed
> [  112.269710] BTRFS info (device dm-6): disk space caching is enabled
> [  112.291430] BTRFS: failed to read the system array on dm-6
> [  112.320104] BTRFS: open_ctree failed
> 
> So dm-6 is: raid0d1 -> ../dm-6
> 
> So, raid0d1 had an issue, btrfs check didn't really report any, for some unknown 
> reason this caused raid0d2 not to be scanned, and in turn this caused
> mounting that filesystem to fail?
> 
> Or did btrfs check actually fix something that I missed?
> Any why would scan have missed raid0d2 the first time around?

I feel confused, too.

Can you grep this message since btrfs dev scan has a "printf("Scanning for Btrfs filesystems\n");"?
And if a scan failed somehow, it may print an error after this message
and we then know what was happening..

> 
> Is it complaining that it can't read btrfs structures from raid0d1 because raid0d2
> wasn't known yet? I'm not too sure what open_ctree means in that context.

No idea about this, not sure if it's due to any dependency?

Thanks,

-liubo

Re: btrfs check --repair is clean, but mount fails

[Anand Jain]

On 02/27/2016 11:03 AM, Marc MERLIN wrote:
> On Fri, Feb 26, 2016 at 06:45:34PM -0800, Liu Bo wrote:
>> On Fri, Feb 26, 2016 at 06:39:38PM -0800, Marc MERLIN wrote:
>>> btrfs-tools 4.4-1
>>> gargamel:~# uname -r
>>> 4.4.2-amd64-i915-volpreempt-20160214bc2
>>>
>>> 2 drive array stopped working after a crash/reboot. Check --repair finds nothing wrong with it:
>>>
>>> gargamel:~# btrfs check --repair /dev/mapper/raid0d1
>>> enabling repair mode
>>> Checking filesystem on /dev/mapper/raid0d1
>>> UUID: 01334b81-c0db-4e80-92e4-cac4da867651
>>> checking extents
>>> Fixed 0 roots.
>>> checking free space cache
>>> cache and super generation don't match, space cache will be invalidated
>>> checking fs roots
>>> checking csums
>>> checking root refs
>>> found 1201345524312 bytes used err is 0
>>> total csum bytes: 1165124220
>>> total tree bytes: 8258322432
>>> total fs tree bytes: 5574197248
>>> total extent tree bytes: 1020428288
>>> btree space waste bytes: 1902023247
>>> file data blocks allocated: 1193398628352
>>>   referenced 1209324777472
>>> gargamel:~# mount /var/local/space
>>> mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
>>>         missing codepage or helper program, or other error
>>>         In some cases useful info is found in syslog - try
>>>         dmesg | tail  or so
>>> [ 8200.511021] BTRFS info (device dm-6): disk space caching is enabled
>>> [ 8200.533030] BTRFS: failed to read the system array on dm-6
>>> [ 8200.582097] BTRFS: open_ctree failed
>>
>> Does 'btrfs dev scan' help?
>
> Oh my, it does...
> gargamel:~# btrfs dev scan
> Scanning for Btrfs filesystems
> gargamel:~# mount /var/local/space
>
> [14477.028083] BTRFS: device label btrfs_space devid 2 transid 776784 /dev/mapper/raid0d2
> [14500.262307] BTRFS info (device dm-7): disk space caching is enabled
> [14504.042485] BTRFS: checking UUID tree
>
> Err, I'm very perplexed now. I already have a scan in my boot process after device decrypts.

   Can you log the output of blkid here. If blkid output does
   not report all the btrfs devs correctly the kernel won't know
   as well.

Thanks, Anand


> Somehow it saw one of my 2 devices, but not the other one?
>
> I'm looking at my boot:
> [  112.063677] BTRFS: device label btrfs_space devid 1 transid 776782 /dev/mapper/raid0d1
> [  112.090192] BTRFS info (device dm-6): disk space caching is enabled
> [  112.111740] BTRFS: failed to read the system array on dm-6
> [  112.160047] BTRFS: open_ctree failed
> [  112.269710] BTRFS info (device dm-6): disk space caching is enabled
> [  112.291430] BTRFS: failed to read the system array on dm-6
> [  112.320104] BTRFS: open_ctree failed
>
> So dm-6 is: raid0d1 -> ../dm-6
>
> So, raid0d1 had an issue, btrfs check didn't really report any, for some unknown
> reason this caused raid0d2 not to be scanned, and in turn this caused
> mounting that filesystem to fail?
>
> Or did btrfs check actually fix something that I missed?
> Any why would scan have missed raid0d2 the first time around?
>
> Is it complaining that it can't read btrfs structures from raid0d1 because raid0d2
> wasn't known yet? I'm not too sure what open_ctree means in that context.
>
> Thanks,
> Marc
>

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Sun, Feb 28, 2016 at 06:58:00AM +0800, Anand Jain wrote:
>   Can you log the output of blkid here. If blkid output does
>   not report all the btrfs devs correctly the kernel won't know
>   as well.

Sure. The relevant entries are at the bottom (last 3 lines).
It looks good now of course, but I how it would have been before I ran a btrfs dev scan

Is there anything helpful in there?

/dev/sdc2: UUID="d9a11ed8-536b-e2d7-2b63-6e45318e24d6" UUID_SUB="c8b717b3-d1bb-9211-f5fd-88b4cad3891a" LABEL="gargamel.svh.merlins.org:12" TYPE="linux_raid_member" PARTUUID="fc061e12-02"
/dev/sdc3: UUID="d98cdbd0-4879-0342-1cb9-3a199281d756" UUID_SUB="c33a26df-abca-4bb2-8064-741d05334129" LABEL="gargamel.svh.merlins.org:13" TYPE="linux_raid_member" PARTUUID="fc061e12-03"
/dev/sdc4: UUID="1a134ab6-0e02-43fa-8704-deed85998155" TYPE="crypto_LUKS" PARTUUID="fc061e12-04"
/dev/sde1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="d10f45f6-52e0-d793-f3e3-b687251a83f5" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="5bd72031-01"
/dev/sdf1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="aee9d2d4-bb18-579a-28f4-f6b15f89a40a" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="23f4b9f6-01"
/dev/sdd1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="db2df41e-1daf-02af-89ed-6e77813e29da" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="90f15dcd-01"
/dev/sda1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="00d115df-f27d-9293-6048-7af099602670" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="06a7af4a-01"
/dev/sdg1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="ca4598ba-de58-5baa-b993-5222e06ac97d" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="bd9db056-9d37-4191-9bd1-353b6a47b487"
/dev/sdh1: UUID="284ccdd7-5516-4ff2-b798-3bc1829c9a04" TYPE="crypto_LUKS" PARTUUID="ca3bb5a5-01"
/dev/sdh2: UUID="7be7e175-8f4c-4f99-94b2-9c904d227045" TYPE="bcache" PARTUUID="ca3bb5a5-02"
/dev/sdj1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="684b477c-81a8-6ce9-222b-1d385aab485c" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="6834173c-d6a9-4da1-8de0-ddf2411557e3"
/dev/sdk1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="7d311e9f-6747-24a5-c962-9fb63739a6e8" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="16d76002-b9f1-4016-8119-a200ec16d4a2"
/dev/sdl1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="cdef3e24-371c-c5d4-a289-16dd0939eff6" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="8b79953b-9f6b-4649-a526-2c61fe07a6f1"
/dev/sdm1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="075571ff-4115-17e9-027f-8c2fcef0457a" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="dd673133-e1a9-46dc-a42b-1554a44a9b28"
/dev/sdi1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="02eae0f6-af27-0529-1d77-09483114b540" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="03d0f2a3-45a4-4172-81e2-1afad7e06d10"
/dev/sdo1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="e8bf196a-9a58-f8de-9472-6f16ab4599d9" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="97573ae8-878b-41bc-b838-e0ea97a54a1b"
/dev/sdn1: UUID="a9bdc59b-51e9-c58e-58d7-48c43de9f367" TYPE="linux_raid_member" PARTUUID="911f14a9-01"
/dev/sdn2: UUID="d9a11ed8-536b-e2d7-2b63-6e45318e24d6" UUID_SUB="d2d23610-d966-dfcb-92c5-b49a3a161964" LABEL="gargamel.svh.merlins.org:12" TYPE="linux_raid_member" PARTUUID="911f14a9-02"
/dev/sdn3: UUID="d98cdbd0-4879-0342-1cb9-3a199281d756" UUID_SUB="9c50a539-3923-840a-e720-66b23d823cc2" LABEL="gargamel.svh.merlins.org:13" TYPE="linux_raid_member" PARTUUID="911f14a9-03"
/dev/sdn4: UUID="01ed40a3-a9f2-4d7d-af14-d57035a5ed55" TYPE="crypto_LUKS" PARTUUID="911f14a9-04"
/dev/sdp1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="4910400c-8e3e-0d32-fdb9-16f8f7ca5f87" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="1bd91aa4-7f0e-4574-9c0e-630c2de9295f"
/dev/sdq1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="497a9a28-4059-842b-25e2-ab31c6d48ded" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="84740d8d-7689-499f-9171-7d0acf8154b7"
/dev/sdr1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="1e3ab905-ba67-7efe-2aaf-cf0d99276e26" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="47aa6022-6a58-4856-87d8-5c4f54212b37"
/dev/md11: UUID="6e06a918-80dc-4f00-8cd3-234939d7172d" TYPE="ext4" PTTYPE="dos"
/dev/md13: UUID="e90613ef-e719-4396-97d2-93ca62c17736" TYPE="crypto_LUKS"
/dev/md5: UUID="2b8cf5be-d74f-43fa-aebd-fed79ba5cb50" TYPE="bcache"
/dev/md6: UUID="ae32d57e-12c3-457a-bc17-4166aa6dde75" TYPE="crypto_LUKS"
/dev/md8: UUID="33b49001-7253-40b3-b617-ea91850a69d9" TYPE="crypto_LUKS"
/dev/bcache0: UUID="c02da1dc-f62b-4232-a0ed-264dae65f16a" TYPE="crypto_LUKS"
/dev/mapper/dshelf1b: UUID="47cf2391-1942-46d1-9690-d597e860a5c6" TYPE="bcache"
/dev/mapper/dshelf2: LABEL="dshelf2" UUID="d4a51178-c1e6-4219-95ab-5c5864695bfd" UUID_SUB="4f46aa7b-23a5-4ad8-8b74-d735d7caf156" TYPE="btrfs"
/dev/mapper/eswap1: UUID="b061e3e6-e775-4cdf-ab2b-1a27ac985888" TYPE="swap"
/dev/mapper/cache1: UUID="16dbdda5-46da-43ef-ac6a-6b81eaed3bb2" TYPE="bcache"
/dev/mapper/oldds1: UUID="79974649-f771-498c-8477-10d076ec3627" UUID_SUB="462789c1-b339-44ba-a53a-a96680e94ac8" TYPE="btrfs"
/dev/mapper/raid0d1: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="a87c0954-e0d5-4cdb-acb9-05ed290c16df" TYPE="btrfs"
/dev/mapper/raid0d2: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="b4ea90fa-4262-489a-830d-3bd4e7518ff2" TYPE="btrfs"
/dev/bcache1: LABEL="dshelf1" UUID="5d0847f8-b243-494a-9e31-0a7c9adbd764" UUID_SUB="f65c681d-f1a1-45f1-a2b5-290358fd9b39" TYPE="btrfs"

-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Sat, Feb 27, 2016 at 10:06:06AM -0800, Liu Bo wrote:
> Can you grep this message since btrfs dev scan has a "printf("Scanning for Btrfs filesystems\n");"?
> And if a scan failed somehow, it may print an error after this message
> and we then know what was happening..

I'm not seeing anything in my console boot log outside of this posted in
my previous message:

Fri Feb 26 14:55:17 2016: raid0d1 (started)...raid0d2 (starting)...
Fri Feb 26 14:55:18 2016: raid0d2 (started)...done.

> > I'm looking at my boot:
> > [  112.063677] BTRFS: device label btrfs_space devid 1 transid 776782 /dev/mapper/raid0d1
> > [  112.090192] BTRFS info (device dm-6): disk space caching is enabled
> > [  112.111740] BTRFS: failed to read the system array on dm-6
> > [  112.160047] BTRFS: open_ctree failed
> > [  112.269710] BTRFS info (device dm-6): disk space caching is enabled
> > [  112.291430] BTRFS: failed to read the system array on dm-6
> > [  112.320104] BTRFS: open_ctree failed
> > 
> > So dm-6 is: raid0d1 -> ../dm-6

btrfs dev scan didn't output any messages from what I can tell, outside
of the dmesg stuff here.

The total messages around that time:
[  110.182362] bcache: bch_journal_replay() journal replay done, 92 keys in 6 entries, seq 8855
[  110.208992] bcache: register_cache() registered cache device dm-4
[  110.236345] bcache: register_bdev() registered backing device dm-1
[  110.316129] bcache: bch_cached_dev_attach() Caching dm-1 as bcache1 on set 0226553a-37cf-41d5-b3ce-8b1e944543a8
[  110.348350] bcache: register_bcache() error opening /dev/md5: device already registered
[  110.445200] Adding 15616764k swap on /dev/mapper/eswap1.  Priority:-1 extents:1 across:15616764k FS
[  111.585812] EXT4-fs (md11): mounted filesystem with ordered data mode. Opts: (null)
[  112.063677] BTRFS: device label btrfs_space devid 1 transid 776782 /dev/mapper/raid0d1
[  112.090192] BTRFS info (device dm-6): disk space caching is enabled
[  112.111740] BTRFS: failed to read the system array on dm-6
[  112.160047] BTRFS: open_ctree failed
[  112.269710] BTRFS info (device dm-6): disk space caching is enabled
[  112.291430] BTRFS: failed to read the system array on dm-6
[  112.320104] BTRFS: open_ctree failed
[  112.332567] BTRFS: device label dshelf1 devid 1 transid 25903 /dev/bcache1
[  112.333076] BTRFS info (device bcache1): disk space caching is enabled
[  112.333077] BTRFS: has skinny extents
[  115.185582] BTRFS: detected SSD devices, enabling SSD mode
[  115.216381] BTRFS: device label dshelf2 devid 1 transid 444834 /dev/mapper/dshelf2
[  115.241607] BTRFS info (device dm-2): disk space caching is enabled
[  115.591923] BTRFS info (device dm-2): bdev /dev/mapper/dshelf2 errs: wr 0, rd 0, flush 0, corrupt 65, gen 0

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901

Re: btrfs check --repair is clean, but mount fails

[Anand Jain]

Marc,

 > Err, I'm very perplexed now. I already have a scan in my boot process
 > after device decrypts.
 > Somehow it saw one of my 2 devices, but not the other one?

If blkid shows both the devices and if you are running 'btrfs dev scan'
during boot, then yes kernel should see both the devices.

Just to be sure, Can you reconfirm if the below blkid output is taken
at the time of the bootup where you are running btrfs dev scan in the
script ?

If you have a choice pls add, 'btrfs fi show -d' as well for the outputs
to be taken at the time of boot just before system's 'btrfs dev scan',

Pls do share your /etc/fstab output for /var/local/space (I guess
you don't have -o degrade option) which is good for this debugging,
which means mount fails if any one of the device is missing.

Thanks, Anand


On 02/28/2016 08:56 AM, Marc MERLIN wrote:
> On Sun, Feb 28, 2016 at 06:58:00AM +0800, Anand Jain wrote:
>>    Can you log the output of blkid here. If blkid output does
>>    not report all the btrfs devs correctly the kernel won't know
>>    as well.
>
> Sure. The relevant entries are at the bottom (last 3 lines).
> It looks good now of course, but I how it would have been before I ran a btrfs dev scan
>
> Is there anything helpful in there?
>
> /dev/sdc2: UUID="d9a11ed8-536b-e2d7-2b63-6e45318e24d6" UUID_SUB="c8b717b3-d1bb-9211-f5fd-88b4cad3891a" LABEL="gargamel.svh.merlins.org:12" TYPE="linux_raid_member" PARTUUID="fc061e12-02"
> /dev/sdc3: UUID="d98cdbd0-4879-0342-1cb9-3a199281d756" UUID_SUB="c33a26df-abca-4bb2-8064-741d05334129" LABEL="gargamel.svh.merlins.org:13" TYPE="linux_raid_member" PARTUUID="fc061e12-03"
> /dev/sdc4: UUID="1a134ab6-0e02-43fa-8704-deed85998155" TYPE="crypto_LUKS" PARTUUID="fc061e12-04"
> /dev/sde1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="d10f45f6-52e0-d793-f3e3-b687251a83f5" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="5bd72031-01"
> /dev/sdf1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="aee9d2d4-bb18-579a-28f4-f6b15f89a40a" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="23f4b9f6-01"
> /dev/sdd1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="db2df41e-1daf-02af-89ed-6e77813e29da" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="90f15dcd-01"
> /dev/sda1: UUID="0d2b91aa-3c93-54d1-5bca-28c1f96f9def" UUID_SUB="00d115df-f27d-9293-6048-7af099602670" LABEL="gargamel.svh.merlins.org:8" TYPE="linux_raid_member" PARTUUID="06a7af4a-01"
> /dev/sdg1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="ca4598ba-de58-5baa-b993-5222e06ac97d" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="bd9db056-9d37-4191-9bd1-353b6a47b487"
> /dev/sdh1: UUID="284ccdd7-5516-4ff2-b798-3bc1829c9a04" TYPE="crypto_LUKS" PARTUUID="ca3bb5a5-01"
> /dev/sdh2: UUID="7be7e175-8f4c-4f99-94b2-9c904d227045" TYPE="bcache" PARTUUID="ca3bb5a5-02"
> /dev/sdj1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="684b477c-81a8-6ce9-222b-1d385aab485c" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="6834173c-d6a9-4da1-8de0-ddf2411557e3"
> /dev/sdk1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="7d311e9f-6747-24a5-c962-9fb63739a6e8" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="16d76002-b9f1-4016-8119-a200ec16d4a2"
> /dev/sdl1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="cdef3e24-371c-c5d4-a289-16dd0939eff6" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="8b79953b-9f6b-4649-a526-2c61fe07a6f1"
> /dev/sdm1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="075571ff-4115-17e9-027f-8c2fcef0457a" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="dd673133-e1a9-46dc-a42b-1554a44a9b28"
> /dev/sdi1: UUID="ec672af7-a66d-9557-2f00-d76c38c9f705" UUID_SUB="02eae0f6-af27-0529-1d77-09483114b540" LABEL="gargamel.svh.merlins.org:5" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="03d0f2a3-45a4-4172-81e2-1afad7e06d10"
> /dev/sdo1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="e8bf196a-9a58-f8de-9472-6f16ab4599d9" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="97573ae8-878b-41bc-b838-e0ea97a54a1b"
> /dev/sdn1: UUID="a9bdc59b-51e9-c58e-58d7-48c43de9f367" TYPE="linux_raid_member" PARTUUID="911f14a9-01"
> /dev/sdn2: UUID="d9a11ed8-536b-e2d7-2b63-6e45318e24d6" UUID_SUB="d2d23610-d966-dfcb-92c5-b49a3a161964" LABEL="gargamel.svh.merlins.org:12" TYPE="linux_raid_member" PARTUUID="911f14a9-02"
> /dev/sdn3: UUID="d98cdbd0-4879-0342-1cb9-3a199281d756" UUID_SUB="9c50a539-3923-840a-e720-66b23d823cc2" LABEL="gargamel.svh.merlins.org:13" TYPE="linux_raid_member" PARTUUID="911f14a9-03"
> /dev/sdn4: UUID="01ed40a3-a9f2-4d7d-af14-d57035a5ed55" TYPE="crypto_LUKS" PARTUUID="911f14a9-04"
> /dev/sdp1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="4910400c-8e3e-0d32-fdb9-16f8f7ca5f87" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="1bd91aa4-7f0e-4574-9c0e-630c2de9295f"
> /dev/sdq1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="497a9a28-4059-842b-25e2-ab31c6d48ded" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="84740d8d-7689-499f-9171-7d0acf8154b7"
> /dev/sdr1: UUID="66bccdfb-afbf-9683-fcf1-f12ef2af2dcb" UUID_SUB="1e3ab905-ba67-7efe-2aaf-cf0d99276e26" LABEL="gargamel.svh.merlins.org:6" TYPE="linux_raid_member" PARTLABEL="primary" PARTUUID="47aa6022-6a58-4856-87d8-5c4f54212b37"
> /dev/md11: UUID="6e06a918-80dc-4f00-8cd3-234939d7172d" TYPE="ext4" PTTYPE="dos"
> /dev/md13: UUID="e90613ef-e719-4396-97d2-93ca62c17736" TYPE="crypto_LUKS"
> /dev/md5: UUID="2b8cf5be-d74f-43fa-aebd-fed79ba5cb50" TYPE="bcache"
> /dev/md6: UUID="ae32d57e-12c3-457a-bc17-4166aa6dde75" TYPE="crypto_LUKS"
> /dev/md8: UUID="33b49001-7253-40b3-b617-ea91850a69d9" TYPE="crypto_LUKS"
> /dev/bcache0: UUID="c02da1dc-f62b-4232-a0ed-264dae65f16a" TYPE="crypto_LUKS"
> /dev/mapper/dshelf1b: UUID="47cf2391-1942-46d1-9690-d597e860a5c6" TYPE="bcache"
> /dev/mapper/dshelf2: LABEL="dshelf2" UUID="d4a51178-c1e6-4219-95ab-5c5864695bfd" UUID_SUB="4f46aa7b-23a5-4ad8-8b74-d735d7caf156" TYPE="btrfs"
> /dev/mapper/eswap1: UUID="b061e3e6-e775-4cdf-ab2b-1a27ac985888" TYPE="swap"
> /dev/mapper/cache1: UUID="16dbdda5-46da-43ef-ac6a-6b81eaed3bb2" TYPE="bcache"
> /dev/mapper/oldds1: UUID="79974649-f771-498c-8477-10d076ec3627" UUID_SUB="462789c1-b339-44ba-a53a-a96680e94ac8" TYPE="btrfs"
> /dev/mapper/raid0d1: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="a87c0954-e0d5-4cdb-acb9-05ed290c16df" TYPE="btrfs"
> /dev/mapper/raid0d2: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="b4ea90fa-4262-489a-830d-3bd4e7518ff2" TYPE="btrfs"
> /dev/bcache1: LABEL="dshelf1" UUID="5d0847f8-b243-494a-9e31-0a7c9adbd764" UUID_SUB="f65c681d-f1a1-45f1-a2b5-290358fd9b39" TYPE="btrfs"
>

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Sun, Feb 28, 2016 at 09:44:36AM +0800, Anand Jain wrote:
> 
> Marc,
> 
> > Err, I'm very perplexed now. I already have a scan in my boot process
> > after device decrypts.
> > Somehow it saw one of my 2 devices, but not the other one?
> 
> If blkid shows both the devices and if you are running 'btrfs dev scan'
> during boot, then yes kernel should see both the devices.
 
Agreed. It has every single time except that one time.

> Just to be sure, Can you reconfirm if the below blkid output is taken
> at the time of the bootup where you are running btrfs dev scan in the
> script ?

It's taken after the problem was fixed with a 2nd btrfs scan. It's a
server doing a 3 day long copy. Can't reboot it right now :)

> If you have a choice pls add, 'btrfs fi show -d' as well for the outputs
> to be taken at the time of boot just before system's 'btrfs dev scan',

I'll do that next time, thanks.

> Pls do share your /etc/fstab output for /var/local/space (I guess
> you don't have -o degrade option) which is good for this debugging,
> which means mount fails if any one of the device is missing.

Nothing fancy:
LABEL=btrfs_space      /var/local/space btrfs   subvol=varlocalspace,defaults,compress=lzo,skip_balance,noatime,noexec 0 0

I'll do more debugging if it happens agian, but I'm pretty sure it was a
one time thing.
Next boot will tell :)

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Sun, Feb 28, 2016 at 09:44:36AM +0800, Anand Jain wrote:
> If you have a choice pls add, 'btrfs fi show -d' as well for the outputs
> to be taken at the time of boot just before system's 'btrfs dev scan',
 
Ok, I had to reboot anyway, so here's the state when it's bad:

gargamel:~# btrfs fi show -d
Label: 'btrfs_boot'  uuid: e4c1daa8-9c39-4a59-b0a9-86297d397f3b
        Total devices 1 FS bytes used 43.52GiB
        devid    1 size 79.93GiB used 62.13GiB path /dev/mapper/cryptroot
 
Label: 'dshelf2'  uuid: d4a51178-c1e6-4219-95ab-5c5864695bfd
        Total devices 1 FS bytes used 4.27TiB
        devid    1 size 7.28TiB used 4.44TiB path /dev/mapper/dshelf2
 
Label: 'btrfs_space'  uuid: 01334b81-c0db-4e80-92e4-cac4da867651
        Total devices 2 FS bytes used 1.09TiB
        devid    1 size 836.13GiB used 641.03GiB path /dev/mapper/raid0d1
        devid    2 size 836.13GiB used 641.03GiB path /dev/mapper/raid0d2
 
Label: 'dshelf1'  uuid: 5d0847f8-b243-494a-9e31-0a7c9adbd764
        Total devices 1 FS bytes used 8.88TiB
        devid    1 size 21.83TiB used 8.92TiB path /dev/bcache1

gargamel:~# mount /var/local/space
mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so
[ 3209.752862] BTRFS info (device dm-6): disk space caching is enabled
[ 3209.775418] BTRFS: failed to read the system array on dm-6
[ 3209.807673] BTRFS: open_ctree failed

blkid shows:
/dev/mapper/raid0d1: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="a87c0954-e0d5-4cdb-acb9-05ed290c16df" TYPE="btrfs" 
/dev/mapper/raid0d2: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="b4ea90fa-4262-489a-830d-3bd4e7518ff2" TYPE="btrfs" 

but mount fails.

And then:
gargamel:~# btrfs dev scan
Scanning for Btrfs filesystems
gargamel:~# mount /var/local/space
gargamel:~# 

Does this make any sense to you?

Thanks,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901

Re: btrfs check --repair is clean, but mount fails

[Anand Jain]

On 02/28/2016 01:17 PM, Marc MERLIN wrote:
> On Sun, Feb 28, 2016 at 09:44:36AM +0800, Anand Jain wrote:
>> If you have a choice pls add, 'btrfs fi show -d' as well for the outputs
>> to be taken at the time of boot just before system's 'btrfs dev scan',
>
> Ok, I had to reboot anyway, so here's the state when it's bad:
>
> gargamel:~# btrfs fi show -d
> Label: 'btrfs_boot'  uuid: e4c1daa8-9c39-4a59-b0a9-86297d397f3b
>          Total devices 1 FS bytes used 43.52GiB
>          devid    1 size 79.93GiB used 62.13GiB path /dev/mapper/cryptroot
>
> Label: 'dshelf2'  uuid: d4a51178-c1e6-4219-95ab-5c5864695bfd
>          Total devices 1 FS bytes used 4.27TiB
>          devid    1 size 7.28TiB used 4.44TiB path /dev/mapper/dshelf2
>
> Label: 'btrfs_space'  uuid: 01334b81-c0db-4e80-92e4-cac4da867651
>          Total devices 2 FS bytes used 1.09TiB
>          devid    1 size 836.13GiB used 641.03GiB path /dev/mapper/raid0d1
>          devid    2 size 836.13GiB used 641.03GiB path /dev/mapper/raid0d2
>
> Label: 'dshelf1'  uuid: 5d0847f8-b243-494a-9e31-0a7c9adbd764
>          Total devices 1 FS bytes used 8.88TiB
>          devid    1 size 21.83TiB used 8.92TiB path /dev/bcache1
>
> gargamel:~# mount /var/local/space
> mount: wrong fs type, bad option, bad superblock on /dev/mapper/raid0d1,
>         missing codepage or helper program, or other error
>         In some cases useful info is found in syslog - try
>         dmesg | tail  or so
> [ 3209.752862] BTRFS info (device dm-6): disk space caching is enabled
> [ 3209.775418] BTRFS: failed to read the system array on dm-6
> [ 3209.807673] BTRFS: open_ctree failed
>
> blkid shows:
> /dev/mapper/raid0d1: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="a87c0954-e0d5-4cdb-acb9-05ed290c16df" TYPE="btrfs"
> /dev/mapper/raid0d2: LABEL="btrfs_space" UUID="01334b81-c0db-4e80-92e4-cac4da867651" UUID_SUB="b4ea90fa-4262-489a-830d-3bd4e7518ff2" TYPE="btrfs"
>
> but mount fails.
>
> And then:
> gargamel:~# btrfs dev scan
> Scanning for Btrfs filesystems
> gargamel:~# mount /var/local/space
> gargamel:~#
>
> Does this make any sense to you?

  Not really. Here we are trying to understand why the first 'btrfs dev
  scan' doesn't help. And, as I understand the first 'btrfs dev scan' is
  during boot up by some system'd script. But the above output seems to
  be taken from the terminal which is after the system has booted up.
  That does not help. We need those commands output during the bootup
  at the time and just before when systemd issues 'btrfs dev scan'.
  Hope I sound clearer now, sorry if it wasn't before.

Thanks, Anand


> Thanks,
> Marc
>

Re: btrfs check --repair is clean, but mount fails

[Duncan]

Marc MERLIN posted on Sat, 27 Feb 2016 19:09:30 -0800 as excerpted:

[line in fstab]
> LABEL=btrfs_space      /var/local/space btrfs subvol=varlocalspace,defaults,compress=lzo,skip_balance,noatime,noexec 0 0

Nothing to do with your issue at hand, but some potentially useful info, FWIW...

The "defaults" mount option in fstab is just that, the defaults, and
doesn't really apply as an option because they /are/ the defaults.  The
only reason for "defaults" as an explicit option to exist is to hold the
options field in the case of no non-default option being there to hold it,
so once there's _any_ non-default option added, "defaults" can be removed,
as the non-default option is now holding the field and the defaults apply
anyway unless overruled by some other option.

Additionally, with any reasonably modern util-linux, the last two fields,
dump and fsck-passno, both default to 0 if not present, so don't need to
be explicitly included if zero, unless of course you want to as a matter of
style, possibly for consistency with other fstab entries where the fields are
needed, perhaps because fsck-passno isn't zero and you need the dump field
of zero as a field-holder to have the non-zero fsck-passno in the correct
field.

Of course neither the two trailing zero fields nor the defaults mount
option do any harm, and you may simply be including them as a matter of
style.  But because the options field in particular can be rather long, as
yours certainly is, knowing that you can skip "defaults" as a mount option
can be quite a useful hint, if you weren't aware of it before.

So FWIW, YMMV, etc, but I thought it might be worth mentioning, for other
readers for whom it might be new and useful info, even if it's "the way
you like it, ****it!" for you. =:^)

FWIW the fstab (5) manpage is the official documentation for it, but it
says effectively what I said above. =:^)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: btrfs check --repair is clean, but mount fails

[Marc MERLIN]

On Sun, Feb 28, 2016 at 06:49:21AM +0000, Duncan wrote:
> The "defaults" mount option in fstab is just that, the defaults, and
> doesn't really apply as an option because they /are/ the defaults.  The

Yeah, been having this for some 20 years, cut and paste, and I should get
used to just removing it :)

> Additionally, with any reasonably modern util-linux, the last two fields,
> dump and fsck-passno, both default to 0 if not present, so don't need to
> be explicitly included if zero, unless of course you want to as a matter of

Correct. That one is mostly style/cut&paste and an fstab that was created in
1999 or so :)

Cheers,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/