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From: Johannes Thumshirn <jthumshirn@suse.de>
To: Nikolay Borisov <nborisov@suse.com>, linux-btrfs@vger.kernel.org
Cc: jeffm@suse.com
Subject: Re: [PATCH 04/15] btrfs: combine device update operations during transaction commit
Date: Tue, 5 Feb 2019 10:21:22 +0100
Message-ID: <ed2ac10d-121c-00cc-3d70-c40fd1f81222@suse.de> (raw)
In-Reply-To: <93ad2335-d23a-2a9e-eec2-3a67347f2cfc@suse.com>

On 04/02/2019 15:48, Nikolay Borisov wrote:
> 
> 
> On 4.02.19 г. 15:25 ч., Johannes Thumshirn wrote:
>> On 30/01/2019 15:50, Nikolay Borisov wrote:
>>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>>> index 888d72dda794..25dab68070dc 100644
>>> --- a/fs/btrfs/disk-io.c
>>> +++ b/fs/btrfs/disk-io.c
>>> @@ -4498,6 +4498,15 @@ void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
>>>  	ASSERT(list_empty(&cur_trans->dirty_bgs));
>>>  	ASSERT(list_empty(&cur_trans->io_bgs));
>>>  
>>> +	while (!list_empty(&cur_trans->dev_update_list)) {
>>> +		struct btrfs_device *dev;
>>> +
>>> +		dev = list_first_entry(&cur_trans->dev_update_list,
>>> +				       struct btrfs_device,
>>> +				       post_commit_list);
>>> +		list_del_init(&dev->post_commit_list);
>>> +	}
>>> +
>>
>> Why not?
>>
>> 	list_for_each_entry_safe(dev, next, &cur_trans->dev_update_list,
>> 				 post_commit_list)
>> 		list_del_init(&dev->post_commit_list);
> 
> Yep, that should work as well, given that there could be no new updates
> in the transaction at the point we are cleaning it up.

Well if there are updates added to the dev_update_list
list_for_each_entry_safe() won't work yes, but if there are concurrent
updates the dev_update_list must be protected by a lock or both of the
above constructs will break into pieces.

	Johannes

-- 
Johannes Thumshirn                            SUSE Labs Filesystems
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-30 14:50 [PATCH 00/15] Improvements to fitrim Nikolay Borisov
2019-01-30 14:50 ` [PATCH 01/15] btrfs: Honour FITRIM range constraints during free space trim Nikolay Borisov
2019-01-31 15:21   ` David Sterba
2019-01-31 15:35     ` Nikolay Borisov
2019-01-31 15:48       ` David Sterba
2019-01-31 19:30       ` Jeff Mahoney
2019-01-31 21:45         ` Nikolay Borisov
2019-01-30 14:50 ` [PATCH 02/15] btrfs: Make WARN_ON in a canonical form Nikolay Borisov
2019-01-31 15:22   ` David Sterba
2019-02-04 13:12   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 03/15] btrfs: Remove EXTENT_FIRST_DELALLOC bit Nikolay Borisov
2019-01-31 15:23   ` David Sterba
2019-02-04 13:15   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 04/15] btrfs: combine device update operations during transaction commit Nikolay Borisov
2019-02-04 13:25   ` Johannes Thumshirn
2019-02-04 14:48     ` Nikolay Borisov
2019-02-05  9:21       ` Johannes Thumshirn [this message]
2019-01-30 14:50 ` [PATCH 05/15] btrfs: Handle pending/pinned chunks before blockgroup relocation during device shrink Nikolay Borisov
2019-02-04 13:29   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 06/15] btrfs: Rename and export clear_btree_io_tree Nikolay Borisov
2019-02-04 13:31   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 07/15] btrfs: Populate ->orig_block_len during read_one_chunk Nikolay Borisov
2019-01-30 14:50 ` [PATCH 08/15] btrfs: Introduce new bits for device allocation tree Nikolay Borisov
2019-01-30 14:50 ` [PATCH 09/15] btrfs: replace pending/pinned chunks lists with io tree Nikolay Borisov
2019-01-30 14:50 ` [PATCH 10/15] btrfs: Remove 'trans' argument from find_free_dev_extent(_start) Nikolay Borisov
2019-02-04 14:36   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 11/15] btrfs: Factor out in_range macro Nikolay Borisov
2019-02-04 13:57   ` Johannes Thumshirn
2019-01-30 14:50 ` [PATCH 12/15] btrfs: Optimize unallocated chunks discard Nikolay Borisov
2019-01-30 14:51 ` [PATCH 13/15] btrfs: Fix gross misnaming Nikolay Borisov
2019-01-30 14:51 ` [PATCH 14/15] btrfs: Implement find_first_clear_extent_bit Nikolay Borisov
2019-02-04 14:04   ` Johannes Thumshirn
2019-02-04 16:57   ` Nikolay Borisov
2019-01-30 14:51 ` [PATCH 15/15] btrfs: Switch btrfs_trim_free_extents to find_first_clear_extent_bit Nikolay Borisov
2019-01-31 15:38   ` [PATCH v2] " Nikolay Borisov
2019-01-31 15:41   ` [PATCH v3] " Nikolay Borisov

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