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From:   harshad shirwadkar <harshadshirwadkar@gmail.com>
Date:   Thu, 23 Dec 2021 12:11:17 -0800
Message-ID: <CAD+ocbxF=GdQdVryoSgbf5uJJk7H0uawLoQTKdDCKfnWgbmuxA@mail.gmail.com>
Subject: Re: [PATCH 1/2] ext4: use ext4_ext_remove_space() for fast commit
 replay delete range
To:     Xin Yin <yinxin.x@bytedance.com>
Cc:     "Theodore Y. Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>,
        linux-kernel@vger.kernel.org
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Precedence: bulk

Looks good to me.

Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>

On Wed, Dec 22, 2021 at 7:24 PM Xin Yin <yinxin.x@bytedance.com> wrote:
>
> For now ,we use ext4_punch_hole() during fast commit replay delete range
> procedure. But it will be affected by inode->i_size, which may not
> correct during fast commit replay procedure. The following test will
> failed.
>
> -create & write foo (len 1000K)
> -falloc FALLOC_FL_ZERO_RANGE foo (range 400K - 600K)
> -create & fsync bar
> -falloc FALLOC_FL_PUNCH_HOLE foo (range 300K-500K)
> -fsync foo
> -crash before a full commit
>
> After the fast_commit reply procedure, the range 400K-500K will not be
> removed. Because in this case, when calling ext4_punch_hole() the
> inode->i_size is 0, and it just retruns with doing nothing.
>
> Change to use ext4_ext_remove_space() instead of ext4_punch_hole()
> to remove blocks of inode directly.
>
> Signed-off-by: Xin Yin <yinxin.x@bytedance.com>
> ---
>  fs/ext4/fast_commit.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> index aa05b23f9c14..3deb97b22ca4 100644
> --- a/fs/ext4/fast_commit.c
> +++ b/fs/ext4/fast_commit.c
> @@ -1708,11 +1708,14 @@ ext4_fc_replay_del_range(struct super_block *sb, struct ext4_fc_tl *tl,
>                 }
>         }
>
> -       ret = ext4_punch_hole(inode,
> -               le32_to_cpu(lrange.fc_lblk) << sb->s_blocksize_bits,
> -               le32_to_cpu(lrange.fc_len) <<  sb->s_blocksize_bits);
> -       if (ret)
> -               jbd_debug(1, "ext4_punch_hole returned %d", ret);
> +       down_write(&EXT4_I(inode)->i_data_sem);
> +       ret = ext4_ext_remove_space(inode, lrange.fc_lblk,
> +                               lrange.fc_lblk + lrange.fc_len - 1);
> +       up_write(&EXT4_I(inode)->i_data_sem);
> +       if (ret) {
> +               iput(inode);
> +               return 0;
> +       }
>         ext4_ext_replay_shrink_inode(inode,
>                 i_size_read(inode) >> sb->s_blocksize_bits);
>         ext4_mark_inode_dirty(NULL, inode);
> --
> 2.20.1
>