Re: [PATCH v2 08/11] xfs: Add xfs_file_dio_write_atomic()

Darrick J. Wong
2025-02-24T20:32:44Z

On Thu, Feb 13, 2025 at 01:56:16PM +0000, John Garry wrote:
> Add xfs_file_dio_write_atomic() for dedicated handling of atomic writes.
>
> In case of -EAGAIN being returned from iomap_dio_rw(), reissue the write
> in CoW-based atomic write mode.
>
> For CoW-based mode, ensure that we have no outstanding IOs which we
> may trample on.
>
> Signed-off-by: John Garry <john.g.garry@oracle.com>

Looks fine,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/xfs/xfs_file.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 258c82cbce12..9762fa503a41 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -619,6 +619,46 @@ xfs_file_dio_write_aligned(
> return ret;
> }
>
> +static noinline ssize_t
> +xfs_file_dio_write_atomic(
> + struct xfs_inode *ip,
> + struct kiocb *iocb,
> + struct iov_iter *from)
> +{
> + unsigned int iolock = XFS_IOLOCK_SHARED;
> + unsigned int dio_flags = 0;
> + ssize_t ret;
> +
> +retry:
> + ret = xfs_ilock_iocb_for_write(iocb, &iolock);
> + if (ret)
> + return ret;
> +
> + ret = xfs_file_write_checks(iocb, from, &iolock);
> + if (ret)
> + goto out_unlock;
> +
> + if (dio_flags & IOMAP_DIO_FORCE_WAIT)
> + inode_dio_wait(VFS_I(ip));
> +
> + trace_xfs_file_direct_write(iocb, from);
> + ret = iomap_dio_rw(iocb, from, &xfs_direct_write_iomap_ops,
> + &xfs_dio_write_ops, dio_flags, NULL, 0);
> +
> + if (ret == -EAGAIN && !(iocb->ki_flags & IOCB_NOWAIT) &&
> + !(dio_flags & IOMAP_DIO_ATOMIC_COW)) {
> + xfs_iunlock(ip, iolock);
> + dio_flags = IOMAP_DIO_ATOMIC_COW | IOMAP_DIO_FORCE_WAIT;
> + iolock = XFS_IOLOCK_EXCL;
> + goto retry;
> + }
> +
> +out_unlock:
> + if (iolock)
> + xfs_iunlock(ip, iolock);
> + return ret;
> +}
> +
> /*
> * Handle block unaligned direct I/O writes
> *
> @@ -723,6 +763,8 @@ xfs_file_dio_write(
> return -EINVAL;
> if ((iocb->ki_pos | count) & ip->i_mount->m_blockmask)
> return xfs_file_dio_write_unaligned(ip, iocb, from);
> + if (iocb->ki_flags & IOCB_ATOMIC)
> + return xfs_file_dio_write_atomic(ip, iocb, from);
> return xfs_file_dio_write_aligned(ip, iocb, from);
> }
>
> --
> 2.31.1
>
>