[PATCH 4/8] xfs: split xfs_file_read_iter into buffered and direct I/O helpers

[Christoph Hellwig <hch@xxxxxx>]

Similar to what we did on the write side a while ago.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/xfs/xfs_file.c | 83 ++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 57 insertions(+), 26 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 09a5a78..e584333 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -239,35 +239,33 @@ xfs_file_fsync(
 }
 
 STATIC ssize_t
-xfs_file_read_iter(
+xfs_file_dio_aio_read(
        struct kiocb            *iocb,
        struct iov_iter         *to)
 {
-       struct file             *file = iocb->ki_filp;
-       struct inode            *inode = file->f_mapping->host;
+       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;
-       size_t                  size = iov_iter_count(to);
+       size_t                  count = iov_iter_count(to);
+       struct xfs_buftarg      *target;
        ssize_t                 ret = 0;
-       loff_t                  pos = iocb->ki_pos;
 
-       XFS_STATS_INC(mp, xs_read_calls);
+       trace_xfs_file_direct_read(ip, count, iocb->ki_pos);
 
-       if ((iocb->ki_flags & IOCB_DIRECT) && !IS_DAX(inode)) {
-               xfs_buftarg_t   *target =
-                       XFS_IS_REALTIME_INODE(ip) ?
-                               mp->m_rtdev_targp : mp->m_ddev_targp;
+       if (XFS_IS_REALTIME_INODE(ip))
+               target = ip->i_mount->m_rtdev_targp;
+       else
+               target = ip->i_mount->m_ddev_targp;
+
+       if (!IS_DAX(inode)) {
                /* DIO must be aligned to device logical sector size */
-               if ((pos | size) & target->bt_logical_sectormask) {
-                       if (pos == i_size_read(inode))
+               if ((iocb->ki_pos | count) & target->bt_logical_sectormask) {
+                       if (iocb->ki_pos == i_size_read(inode))
                                return 0;
                        return -EINVAL;
                }
        }
 
-       if (XFS_FORCED_SHUTDOWN(mp))
-               return -EIO;
-
        /*
         * Locking is a bit tricky here. If we take an exclusive lock for direct
         * IO, we effectively serialise all new concurrent read IO to this file
@@ -279,7 +277,7 @@ xfs_file_read_iter(
         * serialisation.
         */
        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
-       if ((iocb->ki_flags & IOCB_DIRECT) && inode->i_mapping->nrpages) {
+       if (mapping->nrpages) {
                xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
                xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);
 
@@ -294,8 +292,8 @@ xfs_file_read_iter(
                 * flush and reduce the chances of repeated iolock cycles going
                 * forward.
                 */
-               if (inode->i_mapping->nrpages) {
-                       ret = filemap_write_and_wait(VFS_I(ip)->i_mapping);
+               if (mapping->nrpages) {
+                       ret = filemap_write_and_wait(mapping);
                        if (ret) {
                                xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
                                return ret;
@@ -306,23 +304,56 @@ xfs_file_read_iter(
                         * we fail to invalidate a page, but this should never
                         * happen on XFS. Warn if it does fail.
                         */
-                       ret = invalidate_inode_pages2(VFS_I(ip)->i_mapping);
+                       ret = invalidate_inode_pages2(mapping);
                        WARN_ON_ONCE(ret);
                        ret = 0;
                }
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
        }
 
+       ret = generic_file_read_iter(iocb, to);
+       xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+
+       return ret;
+}
+
+STATIC ssize_t
+xfs_file_buffered_aio_read(
+       struct kiocb            *iocb,
+       struct iov_iter         *to)
+{
+       struct xfs_inode        *ip = XFS_I(file_inode(iocb->ki_filp));
+       ssize_t                 ret;
+
+       trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos);
+
+       xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+       ret = generic_file_read_iter(iocb, to);
+       xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+
+       return ret;
+}
+
+STATIC ssize_t
+xfs_file_read_iter(
+       struct kiocb            *iocb,
+       struct iov_iter         *to)
+{
+       struct xfs_mount        *mp = XFS_I(file_inode(iocb->ki_filp))->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)
-               trace_xfs_file_direct_read(ip, size, pos);
+               ret = xfs_file_dio_aio_read(iocb, to);
        else
-               trace_xfs_file_buffered_read(ip, size, pos);
+               ret = xfs_file_buffered_aio_read(iocb, to);
 
-       ret = generic_file_read_iter(iocb, to);
        if (ret > 0)
                XFS_STATS_ADD(mp, xs_read_bytes, ret);
-
-       xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
 }
 
@@ -578,7 +609,7 @@ xfs_file_dio_aio_write(
        end = iocb->ki_pos + count - 1;
 
        /*
-        * See xfs_file_read_iter() for why we do a full-file flush here.
+        * See xfs_file_dio_aio_read() for why we do a full-file flush here.
         */
        if (mapping->nrpages) {
                ret = filemap_write_and_wait(VFS_I(ip)->i_mapping);
-- 
2.1.4