Re: [PATCH v2 3/3] btrfs: update stripe_extent delete loop assumptions

[Qu Wenruo <wqu@suse.com>]

在 2024/7/11 15:51, Johannes Thumshirn 写道:
> From: Johannes Thumshirn <johannes.thumshirn@wdc.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.

> 
> 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@wdc.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);
>   	}
>   
>