use_block_rsv problems with 3.6.1

use_block_rsv problems with 3.6.1

[Stefan Priebe]

Hello,

on i've seen the following backtrace a lot on 3.6.1:
[ 2231.644332] use_block_rsv: 1451 callbacks suppressed
[ 2231.645249] btrfs: block rsv returned -28
[ 2231.645250] ------------[ cut here ]------------
[ 2231.646163] WARNING: at fs/btrfs/extent-tree.c:6323 
use_block_rsv+0x19a/0x1a0 [btrfs]()
[ 2231.647092] Hardware name: Bochs
[ 2231.648051] Modules linked in: ipt_REJECT xt_tcpudp k8temp 
iptable_filter ip_tables x_tables ext2 usbhid microcode i2c_piix4 button 
i2c_core btrfs zlib_deflate lzo_compress sg sd_mod virtio_net uhci_hcd 
ata_generic virtio_scsi ehci_hcd virtio_pci virtio_ring virtio floppy 
usbcore usb_common ata_piix
[ 2231.651137] Pid: 4155, comm: btrfs Tainted: G        W    3.6.1+2-ph #1
[ 2231.652217] Call Trace:
[ 2231.653248]  [<ffffffff8104988a>] warn_slowpath_common+0x7a/0xb0
[ 2231.654296]  [<ffffffff810498d5>] warn_slowpath_null+0x15/0x20
[ 2231.655327]  [<ffffffffa00e91aa>] use_block_rsv+0x19a/0x1a0 [btrfs]
[ 2231.656379]  [<ffffffffa00ed4d8>] btrfs_alloc_free_block+0x38/0x220 
[btrfs]
[ 2231.657377]  [<ffffffff8111d49b>] ? kmem_cache_free+0x1b/0xf0
[ 2231.658347]  [<ffffffffa010f01f>] ? btrfs_get_token_64+0x5f/0xf0 [btrfs]
[ 2231.659293]  [<ffffffffa0112633>] ? read_extent_buffer+0xb3/0x110 [btrfs]
[ 2231.660258]  [<ffffffffa00d96e1>] __btrfs_cow_block+0x121/0x510 [btrfs]
[ 2231.661189]  [<ffffffffa00da0ff>] btrfs_cow_block+0xef/0x200 [btrfs]
[ 2231.662113]  [<ffffffffa00dd149>] btrfs_search_slot+0x359/0x7b0 [btrfs]
[ 2231.663045]  [<ffffffffa00f0de9>] btrfs_del_csums+0x249/0x330 [btrfs]
[ 2231.663980]  [<ffffffffa0113ea7>] ? free_extent_buffer+0x37/0x90 [btrfs]
[ 2231.664938]  [<ffffffffa00eb417>] __btrfs_free_extent+0x547/0x730 [btrfs]
[ 2231.665866]  [<ffffffffa00eb8b1>] run_delayed_data_ref+0x151/0x160 
[btrfs]
[ 2231.666799]  [<ffffffffa00eb972>] run_one_delayed_ref+0xb2/0xc0 [btrfs]
[ 2231.667731]  [<ffffffff8127b3d6>] ? __rb_erase_color+0x166/0x1d0
[ 2231.668692]  [<ffffffffa00eba93>] run_clustered_refs+0x113/0x3a0 [btrfs]
[ 2231.669625]  [<ffffffffa00ebe10>] btrfs_run_delayed_refs+0xf0/0x2f0 
[btrfs]
[ 2231.670563]  [<ffffffffa01075d2>] ? btrfs_orphan_cleanup+0x2a2/0x450 
[btrfs]
[ 2231.671498]  [<ffffffffa00fc0b3>] btrfs_commit_transaction+0xa3/0x9e0 
[btrfs]
[ 2231.672465]  [<ffffffff8106c440>] ? wake_up_bit+0x40/0x40
[ 2231.673399]  [<ffffffffa01247db>] create_subvol+0x4db/0x5e0 [btrfs]
[ 2231.674336]  [<ffffffffa00d4c01>] ? btrfs_set_path_blocking+0x31/0x70 
[btrfs]
[ 2231.675276]  [<ffffffff81055800>] ? inode_capable+0x10/0x20
[ 2231.676257]  [<ffffffffa0126c86>] btrfs_mksubvol+0x176/0x190 [btrfs]
[ 2231.677197]  [<ffffffffa0126dc2>] 
btrfs_ioctl_snap_create_transid+0x122/0x190 [btrfs]
[ 2231.678144]  [<ffffffffa0126e89>] btrfs_ioctl_snap_create+0x59/0x80 
[btrfs]
[ 2231.679080]  [<ffffffff81001772>] ? __switch_to+0x1a2/0x440
[ 2231.680036]  [<ffffffffa012a7b3>] btrfs_ioctl+0x7f3/0x890 [btrfs]
[ 2231.680970]  [<ffffffff814c629d>] ? __schedule+0x3dd/0x700
[ 2231.681896]  [<ffffffff8113bf4b>] do_vfs_ioctl+0x7b/0x380
[ 2231.682814]  [<ffffffff8113c29a>] sys_ioctl+0x4a/0x80
[ 2231.683741]  [<ffffffff814c7f79>] system_call_fastpath+0x16/0x1b
[ 2231.684696] ---[ end trace 2176d16bf8fdb18d ]---

Stefan

Re: use_block_rsv problems with 3.6.1

[Josef Bacik]

On Thu, Oct 11, 2012 at 12:35:48PM -0600, Stefan Priebe wrote:
> Hello,
> 
> on i've seen the following backtrace a lot on 3.6.1:
> [ 2231.644332] use_block_rsv: 1451 callbacks suppressed
> [ 2231.645249] btrfs: block rsv returned -28

Yeah this is the last deep dark corner of ENOSPC, we don't quite hold enough
reserved to handle deleting lots of csums.  Technically this is supposed to be
taken care of by ye olde global block rsv, but in some cases it's not enough.
On the bright side if you are just seeing the warnings then we're able to find
space somewhere and you are a-ok, but it is kind of annoying.  Once I finish my
fsync stuff I'll go back to this problem and try and figure out a real solution.
Thanks,

Josef

Re: use_block_rsv problems with 3.6.1

[Stefan Priebe]

Am 11.10.2012 20:51, schrieb Josef Bacik:
> On Thu, Oct 11, 2012 at 12:35:48PM -0600, Stefan Priebe wrote:
>> Hello,
>>
>> on i've seen the following backtrace a lot on 3.6.1:
>> [ 2231.644332] use_block_rsv: 1451 callbacks suppressed
>> [ 2231.645249] btrfs: block rsv returned -28
>
> Yeah this is the last deep dark corner of ENOSPC, we don't quite hold enough
> reserved to handle deleting lots of csums.  Technically this is supposed to be
> taken care of by ye olde global block rsv, but in some cases it's not enough.
> On the bright side if you are just seeing the warnings then we're able to find
> space somewhere and you are a-ok, but it is kind of annoying.  Once I finish my
> fsync stuff I'll go back to this problem and try and figure out a real solution.
> Thanks,

Pretty strange. As this is a freshly created btrfs - added 3 files and i 
was just:
- creating a read only snapshot
- cat file1 >file4
- creating a read only snapshot
- cat file2 >file5
- creating a read only snapshot
- cat file3 >file6
- creating a read only snapshot

nothing else.

Stefan