[PATCH v2 14/14] fs: xfs: Support setting FMODE_CAN_ATOMIC_WRITE

[John Garry]

For when an inode is enabled for atomic writes, set FMODE_CAN_ATOMIC_WRITE
flag. We check for direct I/O and also check that the bdev can actually
support atomic writes.

We rely on the block layer to reject atomic writes which exceed the bdev
request_queue limits, so don't bother checking any such thing here.

Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
 fs/xfs/xfs_file.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index cecc5428fd7c..e63851be6c15 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1234,6 +1234,25 @@ xfs_file_remap_range(
 	return remapped > 0 ? remapped : ret;
 }
 
+static bool xfs_file_open_can_atomicwrite(
+	struct inode		*inode,
+	struct file		*file)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
+
+	if (!(file->f_flags & O_DIRECT))
+		return false;
+
+	if (!xfs_inode_atomicwrites(ip))
+		return false;
+
+	if (!bdev_can_atomic_write(target->bt_bdev))
+		return false;
+
+	return true;
+}
+
 STATIC int
 xfs_file_open(
 	struct inode	*inode,
@@ -1243,6 +1262,8 @@ xfs_file_open(
 		return -EIO;
 	file->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC | FMODE_BUF_WASYNC |
 			FMODE_DIO_PARALLEL_WRITE | FMODE_CAN_ODIRECT;
+	if (xfs_file_open_can_atomicwrite(inode, file))
+		file->f_mode |= FMODE_CAN_ATOMIC_WRITE;
 	return generic_file_open(inode, file);
 }
 
-- 
2.31.1