Re: [PATCH v2 14/14] fs: xfs: Support setting FMODE_CAN_ATOMIC_WRITE

Dave Chinner
2024-03-06T21:33:44Z

On Mon, Mar 04, 2024 at 01:04:28PM +0000, John Garry wrote:
> For when an inode is enabled for atomic writes, set FMODE_CAN_ATOMIC_WRITE
> flag. We check for direct I/O and also check that the bdev can actually
> support atomic writes.
>
> We rely on the block layer to reject atomic writes which exceed the bdev
> request_queue limits, so don't bother checking any such thing here.
>
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
> fs/xfs/xfs_file.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index cecc5428fd7c..e63851be6c15 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1234,6 +1234,25 @@ xfs_file_remap_range(
> return remapped > 0 ? remapped : ret;
> }
>
> +static bool xfs_file_open_can_atomicwrite(
> + struct inode *inode,
> + struct file *file)
> +{
> + struct xfs_inode *ip = XFS_I(inode);
> + struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> +
> + if (!(file->f_flags & O_DIRECT))
> + return false;
> +
> + if (!xfs_inode_atomicwrites(ip))
> + return false;
> +
> + if (!bdev_can_atomic_write(target->bt_bdev))
> + return false;

Again, this is static blockdev information - the inode atomic write
flag should not be set if the bdev cannot do atomic writes. It
should be checked at mount time - the filesystem probably should
only mount read-only if it is configured to allow atomic writes and
the underlying blockdev does not support atomic writes...

-Dave.
--
Dave Chinner
david@fromorbit.com