[01/20] iomap: better document the IOMAP_F_* flags

Commit Message

Christoph Hellwig Oct. 8, 2019, 7:15 a.m. UTC

The documentation for IOMAP_F_* is a bit disorganized, and doesn't
mention the fact that most flags are set by the file system and consumed
by the iomap core, while IOMAP_F_SIZE_CHANGED is set by the core and
consumed by the file system.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Allison Collins <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
---
 include/linux/iomap.h | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

Patch

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 46ce730b1590..17cf63717681 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -30,21 +30,36 @@  struct vm_fault;
 #define IOMAP_INLINE	0x05	/* data inline in the inode */
 
 /*
- * Flags for all iomap mappings:
+ * Flags reported by the file system from iomap_begin:
+ *
+ * IOMAP_F_NEW indicates that the blocks have been newly allocated and need
+ * zeroing for areas that no data is copied to.
  *
  * IOMAP_F_DIRTY indicates the inode has uncommitted metadata needed to access
  * written data and requires fdatasync to commit them to persistent storage.
+ *
+ * IOMAP_F_SHARED indicates that the blocks are shared, and will need to be
+ * unshared as part a write.
+ *
+ * IOMAP_F_MERGED indicates that the iomap contains the merge of multiple block
+ * mappings.
+ *
+ * IOMAP_F_BUFFER_HEAD indicates that the file system requires the use of
+ * buffer heads for this mapping.
  */
-#define IOMAP_F_NEW		0x01	/* blocks have been newly allocated */
-#define IOMAP_F_DIRTY		0x02	/* uncommitted metadata */
-#define IOMAP_F_BUFFER_HEAD	0x04	/* file system requires buffer heads */
-#define IOMAP_F_SIZE_CHANGED	0x08	/* file size has changed */
+#define IOMAP_F_NEW		0x01
+#define IOMAP_F_DIRTY		0x02
+#define IOMAP_F_SHARED		0x04
+#define IOMAP_F_MERGED		0x08
+#define IOMAP_F_BUFFER_HEAD	0x10
 
 /*
- * Flags that only need to be reported for IOMAP_REPORT requests:
+ * Flags set by the core iomap code during operations:
+ *
+ * IOMAP_F_SIZE_CHANGED indicates to the iomap_end method that the file size
+ * has changed as the result of this write operation.
  */
-#define IOMAP_F_MERGED		0x10	/* contains multiple blocks/extents */
-#define IOMAP_F_SHARED		0x20	/* block shared with another file */
+#define IOMAP_F_SIZE_CHANGED	0x100
 
 /*
  * Flags from 0x1000 up are for file system specific usage: