linux-kernel - Re: [PATCH RFC 07/10] xfs: Add xfs_file_dio_write

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Message-ID: <48acbfac-4f76-4959-b0eb-c205ebf69629@oracle.com>
Date: Mon, 10 Feb 2025 16:59:33 +0000
From: John Garry <john.g.garry@...cle.com>
To: brauner@...nel.org, djwong@...nel.org, cem@...nel.org, dchinner@...hat.com,
        hch@....de
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com,
        ritesh.list@...il.com, martin.petersen@...cle.com
Subject: Re: [PATCH RFC 07/10] xfs: Add xfs_file_dio_write_atomic()

On 04/02/2025 12:01, John Garry wrote:
> +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;
> +	bool			use_cow = false;
> +	unsigned int		dio_flags;
> +	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 (use_cow) {
> +		ret = xfs_reflink_unshare(ip, iocb->ki_pos,
> +			iov_iter_count(from));
> +		if (ret)
> +			goto out_unlock;
> +	}
> +
> +	trace_xfs_file_direct_write(iocb, from);
> +	if (use_cow)
> +		dio_flags = IOMAP_DIO_ATOMIC_COW;

note to self:

We should also set IOMAP_DIO_FORCE_WAIT and call inode_dio_wait() here, 
similar to xfs_file_dio_write_unaligned()

> +	else
> +		dio_flags = 0;
> +
> +	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) && !use_cow) {
> +		xfs_iunlock(ip, iolock);
> +		iolock = XFS_IOLOCK_EXCL;
> +		use_cow = true;
> +		goto retry;
> +	}
> +
> +out_unlock:
> +	if (iolock)
> +		xfs_iunlock(ip, iolock);
> +	return ret;
> +}
> +