linux-kernel - Re: [PATCH v2 07/14] btrfs: implement hole punching for RAID stripe extents

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Message-ID: <CAL3q7H5arrRQJvGPVJzfTsmfX6+xDMemM11sg6Y=aPnXLkCJKQ@mail.gmail.com>
Date: Thu, 9 Jan 2025 15:32:26 +0000
From: Filipe Manana <fdmanana@...nel.org>
To: Johannes Thumshirn <jth@...nel.org>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, 
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Filipe Manana <fdmanana@...e.com>, Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH v2 07/14] btrfs: implement hole punching for RAID stripe extents

On Tue, Jan 7, 2025 at 12:59 PM Johannes Thumshirn <jth@...nel.org> wrote:
>
> From: Johannes Thumshirn <johannes.thumshirn@....com>
>
> If the stripe extent we want to delete starts before the range we want to
> delete and ends after the range we want to delete we're punching a
> hole in the stripe extent:
>
>   |--- RAID Stripe Extent ---|
>   | keep |--- drop ---| keep |
>
> This means we need to a) truncate the existing item and b)
> create a second item for the remaining range.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>

Reviewed-by: Filipe Manana <fdmanana@...e.com>

Looks good, thanks.

> ---
>  fs/btrfs/ctree.c            |  1 +
>  fs/btrfs/raid-stripe-tree.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
>
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index c93f52a30a16028470594de1d1256dbec5c7899c..92071ca0655f0f1920eb841e77d3444a0e0d8834 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -3833,6 +3833,7 @@ static noinline int setup_leaf_for_split(struct btrfs_trans_handle *trans,
>         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
>
>         BUG_ON(key.type != BTRFS_EXTENT_DATA_KEY &&
> +              key.type != BTRFS_RAID_STRIPE_KEY &&
>                key.type != BTRFS_EXTENT_CSUM_KEY);
>
>         if (btrfs_leaf_free_space(leaf) >= ins_len)
> diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
> index 893d963951315abfc734e1ca232b3087b7889431..d15df49c61a86a4188b822b05453428e444920b5 100644
> --- a/fs/btrfs/raid-stripe-tree.c
> +++ b/fs/btrfs/raid-stripe-tree.c
> @@ -138,6 +138,55 @@ int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start, u64 le
>                 trace_btrfs_raid_extent_delete(fs_info, start, end,
>                                                found_start, found_end);
>
> +               /*
> +                * The stripe extent starts before the range we want to delete
> +                * and ends after the range we want to delete, i.e. we're
> +                * punching a hole in the stripe extent:
> +                *
> +                *  |--- RAID Stripe Extent ---|
> +                *  | keep |--- drop ---| keep |
> +                *
> +                * This means we need to a) truncate the existing item and b)
> +                * create a second item for the remaining range.
> +                */
> +               if (found_start < start && found_end > end) {
> +                       size_t item_size;
> +                       u64 diff_start = start - found_start;
> +                       u64 diff_end = found_end - end;
> +                       struct btrfs_stripe_extent *extent;
> +                       struct btrfs_key newkey = {
> +                               .objectid = end,
> +                               .type = BTRFS_RAID_STRIPE_KEY,
> +                               .offset = diff_end,
> +                       };
> +
> +                       /* "right" item */
> +                       ret = btrfs_duplicate_item(trans, stripe_root, path,
> +                                                  &newkey);
> +                       if (ret)
> +                               break;
> +
> +                       item_size = btrfs_item_size(leaf, path->slots[0]);
> +                       extent = btrfs_item_ptr(leaf, path->slots[0],
> +                                               struct btrfs_stripe_extent);
> +
> +                       for (int i = 0; i < btrfs_num_raid_stripes(item_size); i++) {
> +                               struct btrfs_raid_stride *stride = &extent->strides[i];
> +                               u64 phys;
> +
> +                               phys = btrfs_raid_stride_physical(leaf, stride);
> +                               phys += diff_start + length;
> +                               btrfs_set_raid_stride_physical(leaf, stride, phys);
> +                       }
> +
> +                       /* "left" item */
> +                       path->slots[0]--;
> +                       btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
> +                       btrfs_partially_delete_raid_extent(trans, path, &key,
> +                                                          diff_start, 0);
> +                       break;
> +               }
> +
>                 /*
>                  * The stripe extent starts before the range we want to delete:
>                  *
>
> --
> 2.43.0
>
>