Re: [PATCH 7/8] xfs: add DAX IO path support

Brian Foster
2015-04-06T17:49:22Z

On Tue, Mar 24, 2015 at 09:51:05PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> DAX does not do buffered IO (can't buffer direct access!) and hence
> all read/write IO is vectored through the direct IO path. Hence we
> need to add the DAX IO path callouts to the direct IO
> infrastructure.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_aops.c | 35 +++++++++++++++++++++++++++--------
> 1 file changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 3fc5052..97979e9 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1559,6 +1559,30 @@ xfs_end_io_direct_write(
> }
> }
>
> +static inline ssize_t
> +xfs_vm_do_dio(
> + struct inode *inode,
> + int rw,
> + struct kiocb *iocb,
> + struct iov_iter *iter,
> + loff_t offset,
> + void (*endio)(struct kiocb *iocb,
> + loff_t offset,
> + ssize_t size,
> + void *private),
> + int flags)
> +{
> + struct block_device *bdev;
> +
> + if (IS_DAX(inode))
> + return dax_do_io(rw, iocb, inode, iter, offset,
> + xfs_get_blocks_direct, endio, 0);
> +

I assume this is supposed to be get_blocks_direct and not
get_blocks_dax, based on the I/O codepath. The naming is starting to get
a little confusing though. xfs_get_blocks_dax() implies to me that it's
for any DAX I/O, but we only appear to use it internally for
truncate/zeroing/mmap and such. Alas, I can't think of a better name atm
and the code seems Ok to me:

Reviewed-by: Brian Foster <bfoster@redhat.com>

... but a comment somewhere around here and/or at the
xfs_get_blocks_dax() function would be helpful.

Brian

> + bdev = xfs_find_bdev_for_inode(inode);
> + return __blockdev_direct_IO(rw, iocb, inode, bdev, iter, offset,
> + xfs_get_blocks_direct, endio, NULL, flags);
> +}
> +
> STATIC ssize_t
> xfs_vm_direct_IO(
> int rw,
> @@ -1567,17 +1591,12 @@ xfs_vm_direct_IO(
> loff_t offset)
> {
> struct inode *inode = iocb->ki_filp->f_mapping->host;
> - struct block_device *bdev = xfs_find_bdev_for_inode(inode);
>
> if (rw & WRITE) {
> - return __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
> - offset, xfs_get_blocks_direct,
> - xfs_end_io_direct_write, NULL,
> - DIO_ASYNC_EXTEND);
> + return xfs_vm_do_dio(inode, rw, iocb, iter, offset,
> + xfs_end_io_direct_write, DIO_ASYNC_EXTEND);
> }
> - return __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
> - offset, xfs_get_blocks_direct,
> - NULL, NULL, 0);
> + return xfs_vm_do_dio(inode, rw, iocb, iter, offset, NULL, 0);
> }
>
> /*
> --
> 2.0.0
>
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