linux-kernel - Re: [PATCH v2 3/3] btrfs: update stripe

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Message-ID: <ca001842-92f4-46ff-80ee-e7a8a97fc433@suse.com>
Date: Thu, 11 Jul 2024 17:14:50 +0930
From: Qu Wenruo <wqu@...e.com>
To: Johannes Thumshirn <jth@...nel.org>, Chris Mason <clm@...com>,
 Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 Filipe Manana <fdmanana@...e.com>,
 Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH v2 3/3] btrfs: update stripe_extent delete loop
 assumptions



在 2024/7/11 16:25, Qu Wenruo 写道:
> 
> 
> 在 2024/7/11 15:51, Johannes Thumshirn 写道:
>> From: Johannes Thumshirn <johannes.thumshirn@....com>
>>
>> btrfs_delete_raid_extent() was written under the assumption, that it's
>> call-chain always passes a start, length tuple that matches a single
>> extent. But btrfs_delete_raid_extent() is called by
>> do_free_extent_acounting() which in term is called by > 
>> __btrfs_free_extent().
> 
> But from the call site __btrfs_free_extent(), it is still called for a 
> single extent.
> 
> Or we will get an error and abort the current transaction.

Or does it mean, one data extent can have multiple RST entries?

Is that a non-zoned RST specific behavior?
As I still remember that we split ordered extents for zoned devices, so 
that it should always have one extent for each split OE.

Thanks,
Qu
> 
>>
>> But this call-chain passes in a start address and a length that can
>> possibly match multiple on-disk extents.
> 
> Mind to give a more detailed example on this?
> 
> Thanks,
> Qu
> 
>>
>> To make this possible, we have to adjust the start and length of each
>> btree node lookup, to not delete beyond the requested range.
>>
>> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
>> ---
>>   fs/btrfs/raid-stripe-tree.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
>> index fd56535b2289..6f65be334637 100644
>> --- a/fs/btrfs/raid-stripe-tree.c
>> +++ b/fs/btrfs/raid-stripe-tree.c
>> @@ -66,6 +66,11 @@ int btrfs_delete_raid_extent(struct 
>> btrfs_trans_handle *trans, u64 start, u64 le
>>           if (ret)
>>               break;
>> +        start += key.offset;
>> +        length -= key.offset;
>> +        if (length == 0)
>> +            break;
>> +
>>           btrfs_release_path(path);
>>       }
>>
>