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Date:   Mon, 24 Apr 2023 20:54:56 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-nfs@...r.kernel.org, cluster-devel@...hat.com,
        linux-xfs@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
        "Darrick J. Wong" <djwong@...nel.org>,
        linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        David Howells <dhowells@...hat.com>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-ext4@...r.kernel.org, ceph-devel@...r.kernel.org
Subject: Re: [Cluster-devel] [PATCH 05/17] filemap: update ki_pos in generic_perform_write

On Mon, Apr 24, 2023 at 8:22 AM Christoph Hellwig <hch@....de> wrote:
> All callers of generic_perform_write need to updated ki_pos, move it into
> common code.

We've actually got a similar situation with
iomap_file_buffered_write() and its callers. Would it make sense to
fix that up as well?

> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/ceph/file.c | 2 --
>  fs/ext4/file.c | 9 +++------
>  fs/f2fs/file.c | 1 -
>  fs/nfs/file.c  | 1 -
>  mm/filemap.c   | 8 ++++----
>  5 files changed, 7 insertions(+), 14 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index f4d8bf7dec88a8..feeb9882ef635a 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1894,8 +1894,6 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
>                  * can not run at the same time
>                  */
>                 written = generic_perform_write(iocb, from);
> -               if (likely(written >= 0))
> -                       iocb->ki_pos = pos + written;
>                 ceph_end_io_write(inode);
>         }
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 0b8b4499e5ca18..1026acaf1235a0 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -291,12 +291,9 @@ static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
>
>  out:
>         inode_unlock(inode);
> -       if (likely(ret > 0)) {
> -               iocb->ki_pos += ret;
> -               ret = generic_write_sync(iocb, ret);
> -       }
> -
> -       return ret;
> +       if (unlikely(ret <= 0))
> +               return ret;
> +       return generic_write_sync(iocb, ret);
>  }
>
>  static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f4ab23efcf85f8..5a9ae054b6da7d 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4511,7 +4511,6 @@ static ssize_t f2fs_buffered_write_iter(struct kiocb *iocb,
>         current->backing_dev_info = NULL;
>
>         if (ret > 0) {
> -               iocb->ki_pos += ret;
>                 f2fs_update_iostat(F2FS_I_SB(inode), inode,
>                                                 APP_BUFFERED_IO, ret);
>         }
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index 893625eacab9fa..abdae2b29369be 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -666,7 +666,6 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
>                 goto out;
>
>         written = result;
> -       iocb->ki_pos += written;
>         nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
>
>         if (mntflags & NFS_MOUNT_WRITE_EAGER) {
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 2723104cc06a12..0110bde3708b3f 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3960,7 +3960,10 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
>                 balance_dirty_pages_ratelimited(mapping);
>         } while (iov_iter_count(i));
>
> -       return written ? written : status;
> +       if (!written)
> +               return status;
> +       iocb->ki_pos += written;

Could be turned into:
iocb->ki_pos = pos;

> +       return written;
>  }
>  EXPORT_SYMBOL(generic_perform_write);
>
> @@ -4039,7 +4042,6 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>                 endbyte = pos + status - 1;
>                 err = filemap_write_and_wait_range(mapping, pos, endbyte);
>                 if (err == 0) {
> -                       iocb->ki_pos = endbyte + 1;
>                         written += status;
>                         invalidate_mapping_pages(mapping,
>                                                  pos >> PAGE_SHIFT,
> @@ -4052,8 +4054,6 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>                 }
>         } else {
>                 written = generic_perform_write(iocb, from);
> -               if (likely(written > 0))
> -                       iocb->ki_pos += written;
>         }
>  out:
>         current->backing_dev_info = NULL;
> --
> 2.39.2
>

Thanks,
Andreas

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