[RFC 2/8] fs: Reserve inode flag FS_ATOMICWRITES_FL for atomic writes

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

This reserves FS_ATOMICWRITES_FL for flags and adds support in
fileattr to support atomic writes flag & xflag needed for ext4
and xfs.

Co-developed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ioctl.c               | 4 ++++
 include/linux/fileattr.h | 4 ++--
 include/uapi/linux/fs.h  | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 76cf22ac97d7..e0f7fae4777e 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -481,6 +481,8 @@ void fileattr_fill_xflags(struct fileattr *fa, u32 xflags)
 		fa->flags |= FS_DAX_FL;
 	if (fa->fsx_xflags & FS_XFLAG_PROJINHERIT)
 		fa->flags |= FS_PROJINHERIT_FL;
+	if (fa->fsx_xflags & FS_XFLAG_ATOMICWRITES)
+		fa->flags |= FS_ATOMICWRITES_FL;
 }
 EXPORT_SYMBOL(fileattr_fill_xflags);
 
@@ -511,6 +513,8 @@ void fileattr_fill_flags(struct fileattr *fa, u32 flags)
 		fa->fsx_xflags |= FS_XFLAG_DAX;
 	if (fa->flags & FS_PROJINHERIT_FL)
 		fa->fsx_xflags |= FS_XFLAG_PROJINHERIT;
+	if (fa->flags & FS_ATOMICWRITES_FL)
+		fa->fsx_xflags |= FS_XFLAG_ATOMICWRITES;
 }
 EXPORT_SYMBOL(fileattr_fill_flags);
 
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index 47c05a9851d0..ae9329afa46b 100644
--- a/include/linux/fileattr.h
+++ b/include/linux/fileattr.h
@@ -7,12 +7,12 @@
 #define FS_COMMON_FL \
 	(FS_SYNC_FL | FS_IMMUTABLE_FL | FS_APPEND_FL | \
 	 FS_NODUMP_FL |	FS_NOATIME_FL | FS_DAX_FL | \
-	 FS_PROJINHERIT_FL)
+	 FS_PROJINHERIT_FL | FS_ATOMICWRITES_FL)
 
 #define FS_XFLAG_COMMON \
 	(FS_XFLAG_SYNC | FS_XFLAG_IMMUTABLE | FS_XFLAG_APPEND | \
 	 FS_XFLAG_NODUMP | FS_XFLAG_NOATIME | FS_XFLAG_DAX | \
-	 FS_XFLAG_PROJINHERIT)
+	 FS_XFLAG_PROJINHERIT | FS_XFLAG_ATOMICWRITES)
 
 /*
  * Merged interface for miscellaneous file attributes.  'flags' originates from
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index b5b4e1db9576..17f52530f9c8 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -264,6 +264,7 @@ struct fsxattr {
 #define FS_EA_INODE_FL			0x00200000 /* Inode used for large EA */
 #define FS_EOFBLOCKS_FL			0x00400000 /* Reserved for ext4 */
 #define FS_NOCOW_FL			0x00800000 /* Do not cow file */
+#define FS_ATOMICWRITES_FL		0x01000000 /* Inode supports atomic writes */
 #define FS_DAX_FL			0x02000000 /* Inode is DAX */
 #define FS_INLINE_DATA_FL		0x10000000 /* Reserved for ext4 */
 #define FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
-- 
2.43.0