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From: Josef Bacik <josef@toxicpanda.com>
To: Nikolay Borisov <nborisov@suse.com>,
	linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 4/4] btrfs: fix bytes_may_use underflow in prealloc error condtition
Date: Thu, 13 Feb 2020 10:29:16 -0500	[thread overview]
Message-ID: <42fac191-f4a4-ab70-01ce-307c80909905@toxicpanda.com> (raw)
In-Reply-To: <55467ec8-f966-d4f9-d882-8c5881328f77@suse.com>

On 2/13/20 5:17 AM, Nikolay Borisov wrote:
> 
> 
> On 11.02.20 г. 23:40 ч., Josef Bacik wrote:
>> I hit the following warning while running my error injection stress testing
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 3 PID: 1453 at fs/btrfs/space-info.h:108 btrfs_free_reserved_data_space_noquota+0xfd/0x160 [btrfs]
>> RIP: 0010:btrfs_free_reserved_data_space_noquota+0xfd/0x160 [btrfs]
>> Call Trace:
>> btrfs_free_reserved_data_space+0x4f/0x70 [btrfs]
>> __btrfs_prealloc_file_range+0x378/0x470 [btrfs]
>> elfcorehdr_read+0x40/0x40
>> ? elfcorehdr_read+0x40/0x40
>> ? btrfs_commit_transaction+0xca/0xa50 [btrfs]
>> ? dput+0xb4/0x2a0
>> ? btrfs_log_dentry_safe+0x55/0x70 [btrfs]
>> ? btrfs_sync_file+0x30e/0x420 [btrfs]
>> ? do_fsync+0x38/0x70
>> ? __x64_sys_fdatasync+0x13/0x20
>> ? do_syscall_64+0x5b/0x1b0
>> ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> ---[ end trace 70ccb5d0fe51151c ]---
>>
>> This happens if we fail to insert our reserved file extent.  At this
>> point we've already converted our reservation from ->bytes_may_use to
>> ->bytes_reserved.  However once we break we will attempt to free
>> everything from [cur_offset, end] from ->bytes_may_use, but our extent
>> reservation will overlap part of this.
>>
>> Fix this problem by adding ins.offset (our extent allocation size) to
>> cur_offset so we remove the actual remaining part from ->bytes_may_use.
> This contradicts the code, you are adding ins.objectid which is the
> offset and not the size. This means either the code is buggy.

Ooops you're right, I was getting lucky because we're making the whole 
allocation at once, and ins.objectid was past extent_end so we ended up doing 
the right thing, but for the wrong reasons.  In fact I need to adjust this for 
the other error condition, so I'll fix this up.  Thanks,

Josef

  reply	other threads:[~2020-02-13 15:38 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 21:40 [PATCH 0/4] Error condition failure fixes Josef Bacik
2020-02-11 21:40 ` [PATCH 1/4] btrfs: set fs_root = NULL on error Josef Bacik
2020-02-12  0:55   ` Qu Wenruo
2020-02-13 10:05   ` Johannes Thumshirn
2020-02-13 10:48   ` Nikolay Borisov
2020-02-13 15:31     ` Josef Bacik
2020-02-13 15:32       ` Nikolay Borisov
2020-02-11 21:40 ` [PATCH 2/4] btrfs: do not check delayed items are empty for single trans cleanup Josef Bacik
2020-02-12  0:57   ` Qu Wenruo
2020-02-13 10:28   ` Nikolay Borisov
2020-02-13 11:15   ` Johannes Thumshirn
2020-02-11 21:40 ` [PATCH 3/4] btrfs: handle logged extent failure properly Josef Bacik
2020-02-12  0:58   ` Qu Wenruo
2020-02-13 10:26   ` Nikolay Borisov
2020-02-13 11:16   ` Johannes Thumshirn
2020-02-11 21:40 ` [PATCH 4/4] btrfs: fix bytes_may_use underflow in prealloc error condtition Josef Bacik
2020-02-12  1:00   ` Qu Wenruo
2020-02-13 10:17   ` Nikolay Borisov
2020-02-13 15:29     ` Josef Bacik [this message]
2020-02-13 15:47 [PATCH 0/4][v2] Error condition failure fixes Josef Bacik
2020-02-13 15:47 ` [PATCH 4/4] btrfs: fix bytes_may_use underflow in prealloc error condtition Josef Bacik

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