[PATCH] filemap_fdatawrite_range() api: clarify -end parameter

I had trouble understanding working out whether filemap_fdatawrite_range()'s
`end' parameter describes the last-byte-to-be-written or the last-plus-one.
Clarify that in comments.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index d4ff48ec269e..c1b1708cc95d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -175,7 +175,7 @@ static int sync_page(void *word)
  * dirty pages that lie within the byte offsets <start, end>
  * @mapping:    address space structure to write
  * @start:      offset in bytes where the range starts
- * @end:        offset in bytes where the range ends
+ * @end:        offset in bytes where the range ends (inclusive)
  * @sync_mode:  enable synchronous operation
  *
  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
@@ -368,6 +368,12 @@ int filemap_write_and_wait(struct address_space *mapping)
 }
 EXPORT_SYMBOL(filemap_write_and_wait);
 
+/*
+ * Write out and wait upon file offsets lstart->lend, inclusive.
+ *
+ * Note that `lend' is inclusive (describes the last byte to be written) so
+ * that this function can be used to write to the very end-of-file (end = -1).
+ */
 int filemap_write_and_wait_range(struct address_space *mapping,
                                  loff_t lstart, loff_t lend)
 {