Re: [PATCH v2 09/12] btrfs: btrfs: plumb NOWAIT through the write path

[Filipe Manana <fdmanana@kernel.org>]

On Thu, Sep 8, 2022 at 1:26 AM Stefan Roesch <shr@fb.com> wrote:
>
> We have everywhere setup for nowait, plumb NOWAIT through the write path.

Note, there's a double "btrfs: " prefix in the subject line.

>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/btrfs/file.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 4e1745e585cb..6e191e353b22 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1653,8 +1653,9 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
>         bool force_page_uptodate = false;
>         loff_t old_isize = i_size_read(inode);
>         unsigned int ilock_flags = 0;
> +       bool nowait = iocb->ki_flags & IOCB_NOWAIT;

Can be made const.

Thanks.

>
> -       if (iocb->ki_flags & IOCB_NOWAIT)
> +       if (nowait)
>                 ilock_flags |= BTRFS_ILOCK_TRY;
>
>         ret = btrfs_inode_lock(inode, ilock_flags);
> @@ -1710,17 +1711,22 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
>                 extent_changeset_release(data_reserved);
>                 ret = btrfs_check_data_free_space(BTRFS_I(inode),
>                                                   &data_reserved, pos,
> -                                                 write_bytes, false);
> +                                                 write_bytes, nowait);
>                 if (ret < 0) {
>                         int tmp;
>
> +                       if (nowait && (ret == -ENOSPC || ret == -EAGAIN)) {
> +                               ret = -EAGAIN;
> +                               break;
> +                       }
> +
>                         /*
>                          * If we don't have to COW at the offset, reserve
>                          * metadata only. write_bytes may get smaller than
>                          * requested here.
>                          */
>                         tmp = btrfs_check_nocow_lock(BTRFS_I(inode), pos,
> -                                                    &write_bytes, false);
> +                                                    &write_bytes, nowait);
>                         if (tmp < 0)
>                                 ret = tmp;
>                         if (tmp > 0)
> @@ -1737,7 +1743,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
>                 WARN_ON(reserve_bytes == 0);
>                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
>                                                       reserve_bytes,
> -                                                     reserve_bytes, false);
> +                                                     reserve_bytes, nowait);
>                 if (ret) {
>                         if (!only_release_metadata)
>                                 btrfs_free_reserved_data_space(BTRFS_I(inode),
> @@ -1767,10 +1773,11 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
>                 extents_locked = lock_and_cleanup_extent_if_need(
>                                 BTRFS_I(inode), pages,
>                                 num_pages, pos, write_bytes, &lockstart,
> -                               &lockend, false, &cached_state);
> +                               &lockend, nowait, &cached_state);
>                 if (extents_locked < 0) {
> -                       if (extents_locked == -EAGAIN)
> +                       if (!nowait && extents_locked == -EAGAIN)
>                                 goto again;
> +
>                         btrfs_delalloc_release_extents(BTRFS_I(inode),
>                                                        reserve_bytes);
>                         ret = extents_locked;
> --
> 2.30.2
>