[PATCH 20/25] libfuse: add atomic write support

@@ -540,6 +540,8 @@ struct fuse_loop_config_v1 {
  * FUSE_IOMAP_SUPPORT_FILEIO: basic file I/O functionality through iomap
  */
 #define FUSE_IOMAP_SUPPORT_FILEIO	(1ULL << 0)
+/* untorn writes through iomap */
+#define FUSE_IOMAP_SUPPORT_ATOMIC	(1ULL << 1)
 
 /**
  * Connection information, passed to the ->init() method

@@ -1234,6 +1236,8 @@ static inline bool fuse_iomap_need_write_allocate(unsigned int opflags,
 #define FUSE_IFLAG_EXCLUSIVE		(1U << 1)
 /* use iomap for this inode */
 #define FUSE_IFLAG_IOMAP		(1U << 2)
+/* enable untorn writes */
+#define FUSE_IFLAG_ATOMIC		(1U << 3)
 
 /* Which fields are set in fuse_iomap_config_out? */
 #define FUSE_IOMAP_CONFIG_SID		(1 << 0ULL)

@@ -248,6 +248,7 @@
  *  - add FUSE_ATTR_IOMAP to enable iomap for specific inodes
  *  - add FUSE_IOMAP_CONFIG so the fuse server can configure more fs geometry
  *  - add FUSE_NOTIFY_IOMAP_DEV_INVAL to invalidate iomap bdev ranges
+ *  - add FUSE_ATTR_ATOMIC for single-fsblock atomic write support
  */
 
 #ifndef _LINUX_FUSE_H

@@ -591,11 +592,13 @@ struct fuse_file_lock {
  * FUSE_ATTR_EXCLUSIVE: This file can only be modified by this mount, so the
  * kernel can use cached attributes more aggressively (e.g. ACL inheritance)
  * FUSE_ATTR_IOMAP: Use iomap for this inode
+ * FUSE_ATTR_ATOMIC: Enable untorn writes
  */
 #define FUSE_ATTR_SUBMOUNT      (1 << 0)
 #define FUSE_ATTR_DAX		(1 << 1)
 #define FUSE_ATTR_EXCLUSIVE	(1 << 2)
 #define FUSE_ATTR_IOMAP		(1 << 3)
+#define FUSE_ATTR_ATOMIC	(1 << 4)
 
 /**
  * Open flags

@@ -168,6 +168,8 @@ static void convert_stat(const struct stat *stbuf, struct fuse_attr *attr,
 		attr->flags |= FUSE_ATTR_EXCLUSIVE;
 	if (iflags & FUSE_IFLAG_IOMAP)
 		attr->flags |= FUSE_ATTR_IOMAP;
+	if (iflags & FUSE_IFLAG_ATOMIC)
+		attr->flags |= FUSE_ATTR_ATOMIC;
 }
 
 static void convert_attr(const struct fuse_setattr_in *attr, struct stat *stbuf)