Re: [PATCH 09/11] btrfs: Mark pinned log extents as excluded

From: Nikolay Borisov <nborisov@suse.com>
To: dsterba@suse.cz, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 09/11] btrfs: Mark pinned log extents as excluded
Date: Thu, 30 Jan 2020 16:03:40 +0200	[thread overview]
Message-ID: <1b88a583-d90c-58e3-02b2-93c60a097110@suse.com> (raw)
In-Reply-To: <20200130135330.GR3929@twin.jikos.cz>

On 30.01.20 г. 15:53 ч., David Sterba wrote:
> On Mon, Jan 20, 2020 at 04:09:16PM +0200, Nikolay Borisov wrote:
>> In preparation to making pinned extents per-transaction ensure that
>> log such extents are always excluded from caching. To achieve this in
>> addition to marking them via btrfs_pin_extent_for_log_replay they also
>> need to be marked with btrfs_add_excluded_extent to prevent log tree
>> extent buffer being loaded by the free space caching thread. That's
>> required since log treeblocks are not recorded in the extent tree, hence
>> they always look free.
>>
>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
>> ---
>>  fs/btrfs/extent-tree.c | 8 ++++++++
>>  fs/btrfs/tree-log.c    | 2 +-
>>  2 files changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index 7dcf9217a622..d680f2ac336b 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -2634,6 +2634,8 @@ int btrfs_pin_extent_for_log_replay(struct btrfs_trans_handle *trans,
>>  	struct btrfs_block_group *cache;
>>  	int ret;
>>  
>> +	btrfs_add_excluded_extent(trans->fs_info, bytenr, num_bytes);
> 
> Again lack of error handling, I thought that untangling and cleaning up
> the extent pinning was motivated to actually handle the errors.

It is but it will be done in a follow up series. For now I want to have
the pinned extents be per-transaction and not be more broken (e.g. no
error handling) than we currently are.

> 
>> +
>>  	cache = btrfs_lookup_block_group(trans->fs_info, bytenr);
>>  	if (!cache)
>>  		return -EINVAL;
>> @@ -2920,6 +2922,12 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
>>  			mutex_unlock(&fs_info->unused_bg_unpin_mutex);
>>  			break;
>>  		}
>> +		if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags)) {
>> +			clear_extent_bits(&fs_info->freed_extents[0], start,
>> +					  end, EXTENT_UPTODATE);
>> +			clear_extent_bits(&fs_info->freed_extents[1], start,
>> +					  end, EXTENT_UPTODATE);
>> +		}
>>  
>>  		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
>>  			ret = btrfs_discard_extent(fs_info, start,
>> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
>> index b535d409a728..f89de24838d5 100644
>> --- a/fs/btrfs/tree-log.c
>> +++ b/fs/btrfs/tree-log.c
>> @@ -2994,7 +2994,7 @@ static inline void btrfs_remove_log_ctx(struct btrfs_root *root,
>>  	mutex_unlock(&root->log_mutex);
>>  }
>>  
>> -/* 
>> +/*
>>   * Invoked in log mutex context, or be sure there is no other task which
>>   * can access the list.
>>   */
>> -- 
>> 2.17.1