[PATCH 3/6] ext4: Support setting FMODE_CAN_ATOMIC_WRITE

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

FS needs to add the fmode capability in order to support atomic writes
during file open (refer kiocb_set_rw_flags()). Let's check if inode can
support atomic writes then enable FMODE_CAN_ATOMIC_WRITE.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/ext4.h | 7 +++++++
 fs/ext4/file.c | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a41e56c2c628..78475ff14aa2 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3863,6 +3863,13 @@ static inline int ext4_buffer_uptodate(struct buffer_head *bh)
 extern int ext4_block_write_begin(handle_t *handle, struct folio *folio,
 				  loff_t pos, unsigned len,
 				  get_block_t *get_block);
+
+static inline bool ext4_inode_can_atomicwrite(struct inode *inode)
+{
+	return  ext4_test_mount_flag(inode->i_sb, EXT4_MF_ATOMIC_WRITE) &&
+			S_ISREG(inode->i_mode);
+}
+
 #endif	/* __KERNEL__ */
 
 #define EFSBADCRC	EBADMSG		/* Bad CRC detected */
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index b06c5d34bbd2..f9516121a036 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -898,6 +898,9 @@ static int ext4_file_open(struct inode *inode, struct file *filp)
 			return ret;
 	}
 
+	if (ext4_inode_can_atomicwrite(inode))
+		filp->f_mode |= FMODE_CAN_ATOMIC_WRITE;
+
 	filp->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
 	return dquot_file_open(inode, filp);
 }
-- 
2.46.0