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xfs: split direct I/O and DAX path
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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 side effect we also get separate trace points for both I/O types.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Christoph Hellwig authored and Dave Chinner committed Jul 20, 2016
1 parent fa8d972 commit 16d4d43
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Showing 2 changed files with 112 additions and 29 deletions.
139 changes: 110 additions & 29 deletions fs/xfs/xfs_file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -305,13 +305,11 @@ 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;
}

/*
Expand Down Expand Up @@ -360,13 +358,37 @@ 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);
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);
Expand Down Expand Up @@ -399,15 +421,18 @@ 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);

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);
Expand Down Expand Up @@ -755,8 +780,7 @@ 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 */
Expand Down Expand Up @@ -825,14 +849,9 @@ 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) {
Expand All @@ -849,10 +868,70 @@ xfs_file_dio_aio_write(
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;
}

Expand Down Expand Up @@ -934,7 +1013,9 @@ 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);
Expand Down
2 changes: 2 additions & 0 deletions fs/xfs/xfs_trace.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1164,8 +1164,10 @@ 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,
Expand Down

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