Date:   Tue, 29 May 2018 18:41:44 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     overlayfs <linux-unionfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/39] vfs: dedupe: extract helper for a single dedup

On Tue, May 29, 2018 at 5:43 PM, Miklos Szeredi <mszeredi@...hat.com> wrote:
> Extract vfs_dedupe_file_range_one() helper to deal with a single dedup
> request.
>
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
>  fs/read_write.c | 89 +++++++++++++++++++++++++++++++--------------------------
>  1 file changed, 49 insertions(+), 40 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 1818581cadf6..82a53c44c0aa 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1964,6 +1964,44 @@ int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
>  }
>  EXPORT_SYMBOL(vfs_dedupe_file_range_compare);
>
> +static s64 vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
> +                                    struct file *dst_file, loff_t dst_pos,
> +                                    u64 len)
> +{
> +       s64 ret;
> +
> +       ret = mnt_want_write_file(dst_file);
> +       if (ret)
> +               return ret;
> +
> +       ret = clone_verify_area(dst_file, dst_pos, len, true);
> +       if (ret < 0)
> +               goto out_drop_write;
> +
> +       ret = -EINVAL;
> +       if (!(capable(CAP_SYS_ADMIN) || (dst_file->f_mode & FMODE_WRITE)))
> +               goto out_drop_write;
> +
> +       ret = -EXDEV;
> +       if (src_file->f_path.mnt != dst_file->f_path.mnt)
> +               goto out_drop_write;
> +
> +       ret = -EISDIR;
> +       if (S_ISDIR(file_inode(dst_file)->i_mode))
> +               goto out_drop_write;
> +
> +       ret = -EINVAL;
> +       if (!dst_file->f_op->dedupe_file_range)
> +               goto out_drop_write;
> +
> +       ret = dst_file->f_op->dedupe_file_range(src_file, src_pos,
> +                                               dst_file, dst_pos, len);
> +out_drop_write:
> +       mnt_drop_write_file(dst_file);
> +
> +       return ret;
> +}
> +
>  int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
>  {
>         struct file_dedupe_range_info *info;
> @@ -1972,10 +2010,7 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
>         u64 len;
>         int i;
>         int ret;
> -       bool is_admin = capable(CAP_SYS_ADMIN);
>         u16 count = same->dest_count;
> -       struct file *dst_file;
> -       loff_t dst_off;
>         loff_t deduped;
>
>         if (!(file->f_mode & FMODE_READ))
> @@ -2010,54 +2045,28 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same)
>         }
>
>         for (i = 0, info = same->info; i < count; i++, info++) {
> -               struct inode *dst;
>                 struct fd dst_fd = fdget(info->dest_fd);
> +               struct file *dst_file = dst_fd.file;
>
> -               dst_file = dst_fd.file;
>                 if (!dst_file) {
>                         info->status = -EBADF;
>                         goto next_loop;
>                 }
> -               dst = file_inode(dst_file);
> -
> -               ret = mnt_want_write_file(dst_file);
> -               if (ret) {
> -                       info->status = ret;
> -                       goto next_loop;
> -               }
> -
> -               dst_off = info->dest_offset;
> -               ret = clone_verify_area(dst_file, dst_off, len, true);
> -               if (ret < 0) {
> -                       info->status = ret;
> -                       goto next_file;
> -               }
> -               ret = 0;
>
>                 if (info->reserved) {
>                         info->status = -EINVAL;
> -               } else if (!(is_admin || (dst_file->f_mode & FMODE_WRITE))) {
> -                       info->status = -EINVAL;
> -               } else if (file->f_path.mnt != dst_file->f_path.mnt) {
> -                       info->status = -EXDEV;
> -               } else if (S_ISDIR(dst->i_mode)) {
> -                       info->status = -EISDIR;
> -               } else if (dst_file->f_op->dedupe_file_range == NULL) {
> -                       info->status = -EINVAL;
> -               } else {
> -                       deduped = dst_file->f_op->dedupe_file_range(file, off,
> -                                                       dst_file,
> -                                                       info->dest_offset, len);
> -                       if (deduped == -EBADE)
> -                               info->status = FILE_DEDUPE_RANGE_DIFFERS;
> -                       else if (deduped < 0)
> -                               info->status = deduped;
> -                       else
> -                               info->bytes_deduped += deduped;
> +                       goto next_loop;
>                 }
>
> -next_file:
> -               mnt_drop_write_file(dst_file);
> +               deduped = vfs_dedupe_file_range_one(file, off, dst_file,
> +                                                   info->dest_offset, len);
> +               if (deduped == -EBADE)
> +                       info->status = FILE_DEDUPE_RANGE_DIFFERS;
> +               else if (deduped < 0)
> +                       info->status = deduped;
> +               else
> +                       info->bytes_deduped += deduped;
> +
>  next_loop:
>                 fdput(dst_fd);
>

Please note that this patch conflicts with but is also an alternative to commit
227627114799 fs: avoid fdput() after failed fdget() in vfs_dedupe_file_range()
on Al's fixes => for-next branch.

Thanks,
Amir.

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