xfs: pulling read IO path locking up to protect S_DAX checks

From: Dave Chinner <dchinner@redhat.com>

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_file.c | 77 +++++++++++++++++--------------------------------------
 1 file changed, 24 insertions(+), 53 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index b8a4a3f29b36..7d31a0e76b68 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -176,28 +176,12 @@ xfs_file_dio_aio_read(
 	struct kiocb		*iocb,
 	struct iov_iter		*to)
 {
-	struct xfs_inode	*ip = XFS_I(file_inode(iocb->ki_filp));
-	size_t			count = iov_iter_count(to);
-	ssize_t			ret;
-
-	trace_xfs_file_direct_read(ip, count, iocb->ki_pos);
-
-	if (!count)
-		return 0; /* skip atime */
+	trace_xfs_file_direct_read(XFS_I(file_inode(iocb->ki_filp)),
+					iov_iter_count(to), iocb->ki_pos);
 
 	file_accessed(iocb->ki_filp);
-
-	if (iocb->ki_flags & IOCB_NOWAIT) {
-		if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
-			return -EAGAIN;
-	} else {
-		xfs_ilock(ip, XFS_IOLOCK_SHARED);
-	}
-	ret = iomap_dio_rw(iocb, to, &xfs_read_iomap_ops, NULL,
+	return iomap_dio_rw(iocb, to, &xfs_read_iomap_ops, NULL,
 			is_sync_kiocb(iocb));
-	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
-
-	return ret;
 }
 
 static noinline ssize_t
@@ -205,27 +189,12 @@ xfs_file_dax_read(
 	struct kiocb		*iocb,
 	struct iov_iter		*to)
 {
-	struct xfs_inode	*ip = XFS_I(iocb->ki_filp->f_mapping->host);
-	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 */
-
-	if (iocb->ki_flags & IOCB_NOWAIT) {
-		if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
-			return -EAGAIN;
-	} else {
-		xfs_ilock(ip, XFS_IOLOCK_SHARED);
-	}
-
-	ret = dax_iomap_rw(iocb, to, &xfs_read_iomap_ops);
-	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+	trace_xfs_file_dax_read(XFS_I(file_inode(iocb->ki_filp)),
+					iov_iter_count(to), iocb->ki_pos);
 
 	file_accessed(iocb->ki_filp);
-	return ret;
+	return dax_iomap_rw(iocb, to, &xfs_read_iomap_ops);
+
 }
 
 STATIC ssize_t
@@ -233,21 +202,10 @@ 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);
+	trace_xfs_file_buffered_read(XFS_I(file_inode(iocb->ki_filp)),
+					iov_iter_count(to), iocb->ki_pos);
 
-	if (iocb->ki_flags & IOCB_NOWAIT) {
-		if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
-			return -EAGAIN;
-	} else {
-		xfs_ilock(ip, XFS_IOLOCK_SHARED);
-	}
-	ret = generic_file_read_iter(iocb, to);
-	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
-
-	return ret;
+	return generic_file_read_iter(iocb, to);
 }
 
 STATIC ssize_t
@@ -256,7 +214,8 @@ xfs_file_read_iter(
 	struct iov_iter		*to)
 {
 	struct inode		*inode = file_inode(iocb->ki_filp);
-	struct xfs_mount	*mp = XFS_I(inode)->i_mount;
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_mount	*mp = ip->i_mount;
 	ssize_t			ret = 0;
 
 	XFS_STATS_INC(mp, xs_read_calls);
@@ -264,6 +223,16 @@ xfs_file_read_iter(
 	if (XFS_FORCED_SHUTDOWN(mp))
 		return -EIO;
 
+	if (!iov_iter_count(to))
+		return 0; /* skip atime */
+
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
+			return -EAGAIN;
+	} else {
+		xfs_ilock(ip, XFS_IOLOCK_SHARED);
+	}
+
 	if (IS_DAX(inode))
 		ret = xfs_file_dax_read(iocb, to);
 	else if (iocb->ki_flags & IOCB_DIRECT)
@@ -271,6 +240,8 @@ xfs_file_read_iter(
 	else
 		ret = xfs_file_buffered_aio_read(iocb, to);
 
+	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+
 	if (ret > 0)
 		XFS_STATS_ADD(mp, xs_read_bytes, ret);
 	return ret;