On Wed, Jun 22, 2016 at 05:27:15PM +0200, Christoph Hellwig wrote:
> So far the DAX code overloaded the direct I/O code path. There is very little
> in common between the two, and untangling them allows to clean up both variants.
>
> As a ѕide effect we also get separate trace points for both I/O types.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_file.c | 139 ++++++++++++++++++++++++++++++++++++++++++-----------
> fs/xfs/xfs_trace.h | 2 +
> 2 files changed, 112 insertions(+), 29 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 24b267d..0e74325 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -262,13 +262,11 @@ xfs_file_dio_aio_read(
> else
> target = ip->i_mount->m_ddev_targp;
>
> - if (!IS_DAX(inode)) {
> - /* DIO must be aligned to device logical sector size */
> - if ((iocb->ki_pos | count) & target->bt_logical_sectormask) {
> - if (iocb->ki_pos == isize)
> - return 0;
> - return -EINVAL;
> - }
> + /* DIO must be aligned to device logical sector size */
> + if ((iocb->ki_pos | count) & target->bt_logical_sectormask) {
> + if (iocb->ki_pos == isize)
> + return 0;
> + return -EINVAL;
> }
>
> /*
> @@ -317,13 +315,37 @@ xfs_file_dio_aio_read(
> }
>
> data = *to;
> - if (IS_DAX(inode)) {
> - ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct,
> - NULL, 0);
> - } else {
> - ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
> - xfs_get_blocks_direct, NULL, NULL, 0);
> + ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
> + xfs_get_blocks_direct, NULL, NULL, 0);
> + if (ret > 0) {
> + iocb->ki_pos += ret;
> + iov_iter_advance(to, ret);
> }
> + xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
> +
> + file_accessed(iocb->ki_filp);
So I noticed that generic/323 starts crashing in file_accessed -> touch_atime
because iocb->ki_filp->f_path.dentry == NULL. For a while I thought it was
some weird reflink bug, but I finally had time to go build a vanilla 4.8-rc8
kernel and that blew up here too. I'm not sure why this line got inserted
here, since it wasn't there prior to this patch, AFAICT.
<shrug>
--D
> + return ret;
> +}
> +
> +STATIC ssize_t
> +xfs_file_dax_read(
> + struct kiocb *iocb,
> + struct iov_iter *to)
> +{
> + struct address_space *mapping = iocb->ki_filp->f_mapping;
> + struct inode *inode = mapping->host;
> + struct xfs_inode *ip = XFS_I(inode);
> + struct iov_iter data = *to;
> + size_t count = iov_iter_count(to);
> + ssize_t ret = 0;
> +
> + trace_xfs_file_dax_read(ip, count, iocb->ki_pos);
> +
> + if (!count)
> + return 0; /* skip atime */
> +
> + xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
> + ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct, NULL, 0);
> if (ret > 0) {
> iocb->ki_pos += ret;
> iov_iter_advance(to, ret);
> @@ -356,7 +378,8 @@ xfs_file_read_iter(
> struct kiocb *iocb,
> struct iov_iter *to)
> {
> - struct xfs_mount *mp = XFS_I(file_inode(iocb->ki_filp))->i_mount;
> + struct inode *inode = file_inode(iocb->ki_filp);
> + struct xfs_mount *mp = XFS_I(inode)->i_mount;
> ssize_t ret = 0;
>
> XFS_STATS_INC(mp, xs_read_calls);
> @@ -364,7 +387,9 @@ xfs_file_read_iter(
> if (XFS_FORCED_SHUTDOWN(mp))
> return -EIO;
>
> - if (iocb->ki_flags & IOCB_DIRECT)
> + if (IS_DAX(inode))
> + ret = xfs_file_dax_read(iocb, to);
> + else if (iocb->ki_flags & IOCB_DIRECT)
> ret = xfs_file_dio_aio_read(iocb, to);
> else
> ret = xfs_file_buffered_aio_read(iocb, to);
> @@ -586,8 +611,7 @@ xfs_file_dio_aio_write(
> mp->m_rtdev_targp : mp->m_ddev_targp;
>
> /* DIO must be aligned to device logical sector size */
> - if (!IS_DAX(inode) &&
> - ((iocb->ki_pos | count) & target->bt_logical_sectormask))
> + if ((iocb->ki_pos | count) & target->bt_logical_sectormask)
> return -EINVAL;
>
> /* "unaligned" here means not aligned to a filesystem block */
> @@ -656,14 +680,9 @@ xfs_file_dio_aio_write(
> trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
>
> data = *from;
> - if (IS_DAX(inode)) {
> - ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct,
> - xfs_end_io_direct_write, 0);
> - } else {
> - ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
> - xfs_get_blocks_direct, xfs_end_io_direct_write,
> - NULL, DIO_ASYNC_EXTEND);
> - }
> + ret = __blockdev_direct_IO(iocb, inode, target->bt_bdev, &data,
> + xfs_get_blocks_direct, xfs_end_io_direct_write,
> + NULL, DIO_ASYNC_EXTEND);
>
> /* see generic_file_direct_write() for why this is necessary */
> if (mapping->nrpages) {
> @@ -680,10 +699,70 @@ out:
> xfs_rw_iunlock(ip, iolock);
>
> /*
> - * No fallback to buffered IO on errors for XFS. DAX can result in
> - * partial writes, but direct IO will either complete fully or fail.
> + * No fallback to buffered IO on errors for XFS, direct IO will either
> + * complete fully or fail.
> + */
> + ASSERT(ret < 0 || ret == count);
> + return ret;
> +}
> +
> +STATIC ssize_t
> +xfs_file_dax_write(
> + struct kiocb *iocb,
> + struct iov_iter *from)
> +{
> + struct address_space *mapping = iocb->ki_filp->f_mapping;
> + struct inode *inode = mapping->host;
> + struct xfs_inode *ip = XFS_I(inode);
> + struct xfs_mount *mp = ip->i_mount;
> + ssize_t ret = 0;
> + int unaligned_io = 0;
> + int iolock;
> + struct iov_iter data;
> +
> + /* "unaligned" here means not aligned to a filesystem block */
> + if ((iocb->ki_pos & mp->m_blockmask) ||
> + ((iocb->ki_pos + iov_iter_count(from)) & mp->m_blockmask)) {
> + unaligned_io = 1;
> + iolock = XFS_IOLOCK_EXCL;
> + } else if (mapping->nrpages) {
> + iolock = XFS_IOLOCK_EXCL;
> + } else {
> + iolock = XFS_IOLOCK_SHARED;
> + }
> + xfs_rw_ilock(ip, iolock);
> +
> + ret = xfs_file_aio_write_checks(iocb, from, &iolock);
> + if (ret)
> + goto out;
> +
> + /*
> + * Yes, even DAX files can have page cache attached to them: A zeroed
> + * page is inserted into the pagecache when we have to serve a write
> + * fault on a hole. It should never be dirtied and can simply be
> + * dropped from the pagecache once we get real data for the page.
> */
> - ASSERT(ret < 0 || ret == count || IS_DAX(VFS_I(ip)));
> + if (mapping->nrpages) {
> + ret = invalidate_inode_pages2(mapping);
> + WARN_ON_ONCE(ret);
> + }
> +
> + if (iolock == XFS_IOLOCK_EXCL && !unaligned_io) {
> + xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
> + iolock = XFS_IOLOCK_SHARED;
> + }
> +
> + trace_xfs_file_dax_write(ip, iov_iter_count(from), iocb->ki_pos);
> +
> + data = *from;
> + ret = dax_do_io(iocb, inode, &data, xfs_get_blocks_direct,
> + xfs_end_io_direct_write, 0);
> + if (ret > 0) {
> + iocb->ki_pos += ret;
> + iov_iter_advance(from, ret);
> + }
> +out:
> + xfs_rw_iunlock(ip, iolock);
> return ret;
> }
>
> @@ -765,7 +844,9 @@ xfs_file_write_iter(
> if (XFS_FORCED_SHUTDOWN(ip->i_mount))
> return -EIO;
>
> - if ((iocb->ki_flags & IOCB_DIRECT) || IS_DAX(inode))
> + if (IS_DAX(inode))
> + ret = xfs_file_dax_write(iocb, from);
> + else if (iocb->ki_flags & IOCB_DIRECT)
> ret = xfs_file_dio_aio_write(iocb, from);
> else
> ret = xfs_file_buffered_aio_write(iocb, from);
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 2504f94..1451690 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -1165,8 +1165,10 @@ DEFINE_EVENT(xfs_file_class, name, \
> TP_ARGS(ip, count, offset))
> DEFINE_RW_EVENT(xfs_file_buffered_read);
> DEFINE_RW_EVENT(xfs_file_direct_read);
> +DEFINE_RW_EVENT(xfs_file_dax_read);
> DEFINE_RW_EVENT(xfs_file_buffered_write);
> DEFINE_RW_EVENT(xfs_file_direct_write);
> +DEFINE_RW_EVENT(xfs_file_dax_write);
> DEFINE_RW_EVENT(xfs_file_splice_read);
>
> DECLARE_EVENT_CLASS(xfs_page_class,
> --
> 2.1.4
>
> _______________________________________________
> xfs mailing list
> xfs@xxxxxxxxxxx
> http://oss.sgi.com/mailman/listinfo/xfs
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
