Re: Delayed inode operations not doing the right thing with enospc

[Josef Bacik <josef@redhat.com>]

On 06/06/2011 09:39 PM, Miao Xie wrote:
> On fri, 03 Jun 2011 14:46:10 -0400, Josef Bacik wrote:
>> I got a lot of these when running stress.sh on my test box
>>
>> [ 9792.654889] ------------[ cut here ]------------
>> [ 9792.654898] WARNING: at fs/btrfs/extent-tree.c:5681
>> btrfs_alloc_free_block+0xca/0x27c [btrfs]()
>> [ 9792.654899] Hardware name: To Be Filled By O.E.M.
>> [ 9792.654900] Modules linked in: btrfs zlib_deflate libcrc32c
>> ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables
>> arc4 rt61pci rt2x00pci rt2x00lib snd_hda_codec_hdmi mac80211
>> snd_hda_codec_realtek cfg80211 snd_hda_intel edac_core snd_seq rfkill
>> pcspkr serio_raw snd_hda_codec eeprom_93cx6 edac_mce_amd sp5100_tco
>> i2c_piix4 k10temp snd_hwdep snd_seq_device snd_pcm floppy r8169 xhci_hcd
>> mii snd_timer snd soundcore snd_page_alloc ipv6 firewire_ohci pata_acpi
>> ata_generic firewire_core pata_via crc_itu_t radeon ttm drm_kms_helper
>> drm i2c_algo_bit i2c_core [last unloaded: scsi_wait_scan]
>> [ 9792.654919] Pid: 2762, comm: rm Tainted: G        W   2.6.39+ #1
>> [ 9792.654920] Call Trace:
>> [ 9792.654922]  [<ffffffff81053c4a>] warn_slowpath_common+0x83/0x9b
>> [ 9792.654925]  [<ffffffff81053c7c>] warn_slowpath_null+0x1a/0x1c
>> [ 9792.654933]  [<ffffffffa038e747>] btrfs_alloc_free_block+0xca/0x27c
>> [btrfs]
>> [ 9792.654945]  [<ffffffffa03b8562>] ? map_extent_buffer+0x6e/0xa8 [btrfs]
>> [ 9792.654953]  [<ffffffffa038189b>] __btrfs_cow_block+0xfc/0x30c [btrfs]
>> [ 9792.654963]  [<ffffffffa0396aa6>] ? btrfs_buffer_uptodate+0x47/0x58
>> [btrfs]
>> [ 9792.654970]  [<ffffffffa0382e48>] ? read_block_for_search+0x94/0x368
>> [btrfs]
>> [ 9792.654978]  [<ffffffffa0381ba9>] btrfs_cow_block+0xfe/0x146 [btrfs]
>> [ 9792.654986]  [<ffffffffa03848b0>] btrfs_search_slot+0x14d/0x4b6 [btrfs]
>> [ 9792.654997]  [<ffffffffa03b8562>] ? map_extent_buffer+0x6e/0xa8 [btrfs]
>> [ 9792.655022]  [<ffffffffa03938e8>] btrfs_lookup_inode+0x2f/0x8f [btrfs]
>> [ 9792.655025]  [<ffffffff8147afac>] ? _cond_resched+0xe/0x22
>> [ 9792.655027]  [<ffffffff8147b892>] ? mutex_lock+0x29/0x50
>> [ 9792.655039]  [<ffffffffa03d41b1>]
>> btrfs_update_delayed_inode+0x72/0x137 [btrfs]
>> [ 9792.655051]  [<ffffffffa03d4ea2>] btrfs_run_delayed_items+0x90/0xdb
>> [btrfs]
>> [ 9792.655062]  [<ffffffffa039a69b>]
>> btrfs_commit_transaction+0x228/0x654 [btrfs]
>> [ 9792.655064]  [<ffffffff8106e8da>] ? remove_wait_queue+0x3a/0x3a
>> [ 9792.655075]  [<ffffffffa03a2fa5>] btrfs_evict_inode+0x14d/0x202 [btrfs]
>> [ 9792.655077]  [<ffffffff81132bd6>] evict+0x71/0x111
>> [ 9792.655079]  [<ffffffff81132de0>] iput+0x12a/0x132
>> [ 9792.655081]  [<ffffffff8112aa3a>] do_unlinkat+0x106/0x155
>> [ 9792.655083]  [<ffffffff81127b83>] ? path_put+0x1f/0x23
>> [ 9792.655085]  [<ffffffff8109c53c>] ? audit_syscall_entry+0x145/0x171
>> [ 9792.655087]  [<ffffffff81128410>] ? putname+0x34/0x36
>> [ 9792.655090]  [<ffffffff8112b441>] sys_unlinkat+0x29/0x2b
>> [ 9792.655092]  [<ffffffff81482c42>] system_call_fastpath+0x16/0x1b
>> [ 9792.655093] ---[ end trace 02b696eb02b3f768 ]---
>>
>>
>> This is because use_block_rsv() is having to do a
>> reserve_metadata_bytes(), which shouldn't happen as we should have
>> reserved enough space for those operations to complete.  This is
>> happening because use_block_rsv() will call get_block_rsv(), which if
>> root->ref_cows is set (which is the case on all fs roots) we will use
>> trans->block_rsv, which will only have what the current transaction
>> starter had reserved.
>>
>> What needs to be done instead is we need to have a block reserve that
>> any reservation that is done at create time for these inodes is migrated
>> to this special reserve, and then when you run the delayed inode items
>> stuff you set trans->block_rsv to the special block reserve so the
>> accounting is all done properly.
>>
>> This is just off the top of my head, there may be a better way to do it,
>> I've not actually looked that the delayed inode code at all.
>>
>> I would do this myself but I have a ever increasing list of shit to do
>> so will somebody pick this up and fix it please?  Thanks,
>
> Sorry, it's my miss.
> I forgot to set trans->block_rsv to global_block_rsv, since we have migrated
> the space from trans_block_rsv to global_block_rsv.
>
> I'll fix it soon.
>

Great thanks Miao,

Josef