Re: [PATCH v2 05/12] btrfs: add btrfs_try_lock_ordered_range

[Filipe Manana <fdmanana@kernel.org>]

On Thu, Sep 8, 2022 at 1:26 AM Stefan Roesch <shr@fb.com> wrote:
>
> From: Josef Bacik <josef@toxicpanda.com>
>
> For IOCB_NOWAIT we're going to want to use try lock on the extent lock,
> and simply bail if there's an ordered extent in the range because the
> only choice there is to wait for the ordered extent to complete.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/btrfs/ordered-data.c | 28 ++++++++++++++++++++++++++++
>  fs/btrfs/ordered-data.h |  1 +
>  2 files changed, 29 insertions(+)
>
> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> index 1952ac85222c..3cdfdcedb088 100644
> --- a/fs/btrfs/ordered-data.c
> +++ b/fs/btrfs/ordered-data.c
> @@ -1041,6 +1041,34 @@ void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
>         }
>  }
>
> +/*
> + * btrfs_try_lock_ordered_range - lock the passed range and ensure all pending
> + * ordered extents in it are run to completion in nowait mode.
> + *
> + * @inode:        Inode whose ordered tree is to be searched
> + * @start:        Beginning of range to flush
> + * @end:          Last byte of range to lock
> + *
> + * This function returns 1 if btrfs_lock_ordered_range does not return any
> + * extents, otherwise 0.

Why not a bool, true/false? That's all that is needed, and it's clear.

Thanks.

> + */
> +int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end)
> +{
> +       struct btrfs_ordered_extent *ordered;
> +
> +       if (!try_lock_extent(&inode->io_tree, start, end))
> +               return 0;
> +
> +       ordered = btrfs_lookup_ordered_range(inode, start, end - start + 1);
> +       if (!ordered)
> +               return 1;
> +
> +       btrfs_put_ordered_extent(ordered);
> +       unlock_extent(&inode->io_tree, start, end);
> +       return 0;
> +}
> +
> +
>  static int clone_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pos,
>                                 u64 len)
>  {
> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> index 87792f85e2c4..ec27ebf0af4b 100644
> --- a/fs/btrfs/ordered-data.h
> +++ b/fs/btrfs/ordered-data.h
> @@ -218,6 +218,7 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr,
>  void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
>                                         u64 end,
>                                         struct extent_state **cached_state);
> +int btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end);
>  int btrfs_split_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pre,
>                                u64 post);
>  int __init ordered_data_init(void);
> --
> 2.30.2
>